Euphorbia pulcherrima

PEST

   NAME

     Whitefly, Snow flies

     Various Whitefly Species

   ORDER

     Hemiptera

   FAMILY

     Aleyrodidae

Description of the Pest

This is a small sap sucking moth-like insect up to 3mm long with winged adults that have a covering of fine white powder, hence the common name. The wings are folded flat over the body and males live for one month and females live up to three months. The eggs are laid on the underside of the leaf and the wingless nymphs are immobile, flattened-round scale -like with a fringe of waxy filaments. The nymphs are translucent to greenish, congregating on young plant tissue and both adults and nymphs suck sap and producing honeydew.  

There are several species such as Ash whitefly (Siphoninus phillyreae), Tobacco whitefly (Bemesia tabaci), Silverleaf whitefly and Spiralling whitefly (Aleurodicus disperses)

Greenhouse whitefly (Trialeurodes vaporariorum)

This species of whitefly normally grow to 2mm long with two pairs of wings. Their colour is due to a covering of a fine white wax and the insect has a white-moth appearance. If disturbed the insects swarm and resettle on the plant quickly. The first nymphal stage is mobile and the later stage is scale-like with fine waxy marginal hairs. These nymphal stages produce honeydew, which encourages sooty mould. It is a persistent pest commonly found in glasshouses.

Adult                   Appearance under the leaf

The Hakea Whitefly (Synaleurodicus hakeae) is a small, moth-like up to 0.15mm wide with wings that have a powdery coating and produce flattened scale-like nymphs. Both adult and nymph gather together in colonies and suck sap.

Appearance and Distribution of the Pest

The eggs are laid during the spring and the adults tend to stay on the underside of the leaf until disturbed, when they fly in mass and may infect other plants. Many plants are only susceptible to this insect when cultivated under glass.

Life Cycle

This insect has a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.

White flies have a gradual metamorphosis, egg and four nymphal stages. One generation occurs from three to eight weeks and is dependant on the current weather. Hundreds of eggs are deposited on the underside of leaves in arch or circles each with a short stalk.

Eggs laid in a pattern      Eggs laid in a pattern

After hatching the first nymphal stage wanders around on the leaf surface for several days. Then selects a place to suck sap where it goes through all nymphal stages emerging as an adult after the fourth stage.

Period of Activity

This peat is found from tropical to temperate regions and is most active during warm weather. It is difficult to predict an infestation, as some years it is severe and other years it is absent. In glasshouse conditions it is often a problem and may extend outside the normal period of activity. They overwinter in the egg stage or find sheltered places to hide.

Damage Caused

Affected plants have leaves with yellowish to white mottling on the upper surface or with shiny secretions on new shoots or on the underside. Heavy infestations cause leaves to wilt and sooty mould to appear on the honeydew. Plant looses vigour and in some cases die.

                  Tagetes erecta

Susceptible Plants

Whiteflies attack a wide range of plants affected by this insect, including Abutilon, Boronia, Hibiscus and Fuchsia species. Citrus, Vegetables, Ferns and certain weed species are venerable. Australian native plants are also attacked, such as the Hakea species.

Greenhouse whitefly (Trialeurodes vaporariorum) attacks a wide range of ornamental plants, weeds and vegetables including; Phaseolus (beans), Lycopersicon  (tomatoes), potatoes, Cucumis (cucurbits), Lactuca (lettuce), Dendranthema (Chrysanthemum), Dahlia and Hibiscus species.

Several ferns, including Adiantum, Asplenium, Davallia, Nephrolepis, Onychium, Platycerium and Pteris species are attacked with nymphs congregating on the underside of the fronds, normally causing little damage.

Rhododendron species are attacked by the Rhododendron White Fly (Dialeurodes chittendeni) causing yellowish mottled appearance on the upper surface of the leaf.

Cultural Control

It is difficult to control with out the application of chemicals, though strong jets of water greatly disturb the colonies. Companion plantings with basil or other aromatic plants deters white flies or spray the plants with onion-garlic spray.

In an enclosed environment sticky fly paper can reduce numbers. When the nymphal stage is found an application of white oil will reduce numbers.

Biological Control

A parasitic wasp (Encarsia Formosa) attacks nymphal stages reducing numbers. Other predators include small birds, spiders, ladybirds and there lava, hover flies, damsel flies and mantids.

Chemical Control

Plants may be sprayed with Dimethoate, permethrin, bifenthrin or pirimiphos-methyl, but some insects have immunity to chemicals. The pest may also be sprayed with a mixture of white oil and nicotine sulphate or pyrethrum.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

PEST

 

   NAME

     Mealybugs

     Various Mealybug Species

 

   ORDER

     Hemiptera

 

   FAMILY

     Pseudococcidae

 

Description of the Pest

Adult females are 3-5mm long, flattened oval-shaped white insects, which secrete a white, mealy wax that forms a row of hair-like filaments of fairly uniform length around the edge of the body; the hind end bears one or two pairs of filaments that are longer than the others. They are mobile but slow-moving. The seldom-seen adult males are tiny winged insects with a pair of long waxy tail filaments. Early stage nymphs are tiny, pink and mobile; later stages resemble adult females.

 

                 

 

There are many types of mealybugs including;

·        Longtailed Mealybugs (Pseudococcus longispinus) generally have tail filaments that are longer than there body. If squashed yellow body fluid is revealed and the eggs are laid under the body and normally hatch immediately.

 

·        Citrus Mealybug (Planococcus citri). This insect has tail filaments that are less than 1/3 the length of its body. It produces yellow orange body fluid and lays eggs in a cottony mass.

 

·        Citrophilous Mealybug ( Pseudococcus calceolariae). This insect has tail filaments that are about 1/3 the length of its body. It produces dark red body fluid and the eggs are laid in a cottony sac.

 

·        Root Mealybug (Rhizeocus falcifer). This insect is not normally seen but produces a open white mass as it feeds on the outer or terminal roots, normally container plants, particularly cacti species. The eggs are laid in the waxy mass and adults may dispersed by ants.

 

·        Hibiscus Mealybug (Maconellicoccus hirsutus)

·        Tuber Mealybug (Pseudococcus affinis)

 

The Mealybugs (Pseudococcus  adonidum) and (Planococcus citri) are a major pest of cacti species,  sucking sap and turning the infected area yellow. These pests are also found on Strelitzia, Camellia and Yucca species.

 

Appearance and Distribution of the Pest

Mealy bugs are found worldwide. The above ground species are found in sheltered areas such as under a leaf or in leaf bases. They are also found where two fruits or leaves touch and are not readily noticeable.

 

The below ground species are only found when a plant is re-potted or the infected plant wilts and dies. Mealybugs are distributed several ways including slowly walking to a new host or transferred on clothing, contaminated plants or strong wind and on visiting insects. They are also farmed by ants which in a nursery situation infest pots by tunnelling and carrying mealybugs to the roots.

 

Attending Ants

 

Life Cycle

These insects have a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.

Up to 200 young are produced in 2-3 weeks; eggs may hatch as they are being laid. The life cycle includes eggs, nymphs (3 to 4 stages) to adult takes 6 weeks, in warmer months; several generations appear throughout the year.

 

Period of Activity

Active all year, particularly in spring and autumn. Warm, humid conditions are preferred and the insect overwinter outdoors as eggs. These may be found on surrounding weeds. In Citrus species many longtailed mealybugs overwinter as juveniles, maturing during spring. In a Glasshouse conditions mealybugs are active through the year.

 

Damage Caused

Adults and nymphs suck sap, congregating in sheltered parts of the plants; some species feed undetected on roots. Early infestations may go unnoticed until the plant begins to wilt. The insect also produces honeydew, which gives rise to sooty mould.

 

         Clivia miniata

 

Susceptible Plants

Mealybugs are found on a wide variety of trees and shrubs. They are also destructive to many ornamentals; including indoor plants (especially African violets and ferns), and are a major greenhouse pest.

 

Cactus species

Many species of mealybug are common pest of cactus and succulents.  The small, grey to light brown mealy bugs are difficult to see amongst the spines. Nesting females appear as the small balls of white fluff on cactus spines or around the base and under the rim of the pots.  The female will produce eggs or living nymphs and the insect will produce honeydew that attracts ants.  Ants should be discouraged as they farm mealy bugs, moving them from one place to another in a cactus collection.

Cactus is also attacked by the root mealybugs that infest the roots of plants and their damage allows fungal and bacterial infections to enter the plant tissue.  They can be identified by white fluffy deposits in the soil or underneath a pot and appeared as tiny pinkish brown wood lice up to 3 mm long.

 

Catalpa species are susceptible to the mealybug (Pseudococcus comstocki) which is a wax covered mealybug that causes distorted growth of the branches and branchlets.

 

Fern species are commonly attacked by mealy bugs and can be recognised by small white, waxy secretions as it feeds in the crevices at vein junctions or on the exposed rhizome.

 

Hedera and Crassula species are susceptible to three species of mealybugs including Citrus Mealybug (Planococcus citri) and not normally requiring control.

 

Laburnum anagyroides is infested with the Grape Mealybug (Pseudococcus maritimus) infesting the branches and twigs.

 

Plumeria acutifolia becomes infested with mealybugs on the new growth but normally control is not required.

 

Psidium species are attacked by the Longtailed Mealybugs (Pseudococcus longispinus).

 

Sequoia species are attacked by three species of Mealybugs including (Planococcus citri).

 

Thymus species are attacked by the Root Mealybug (Rhizeocus falcifer).

 

Thuja species Cupressus macrocarpa and Araucaria heterophylla are can be infested with the mealybugs (Pseudococcus ryani).

 

Turf Grass may be infested with mealybugs causing severs damage and often go undetected and build up large colonies quickly. The turf forms brown dry patches and looks simular to Dollar Spot the infestation may also occur around core holes and can be discouraged by generous watering. Agrostis palustris (Bent) and Cynodon species (Couch) are commonly attacked.

 

Yucca species are attacked by the mealybug (Planococcus citri).

 

Cultural Control

Small plants may be sprayed with a soapy water solution or sponged down preferably during the evening. Heavily infected areas should be pruned and destroyed or the whole plant removed. Infested pot-plants should be discarded and thoroughly disinfect pots before recycling). Maintain vigour by watering to replace sap loss, this helps infected plants to recover.

As a preventative measure for root mealybugs grind up mothballs and add them to the potting mix to discourage infestations.  Care should be taken as the chemicals in mothballs can damage plastic pots (use clay pots) and in some countries such as the UK. mothballs must be used as directed on the label.

 

Biological Control

Lacewing and ladybeetle larvae (Cryptolaemus montrouzeri) control small infestations. This predator insect requires temperatures of at least 21° C. (70°F) and in small infestations it is difficult to maintain a balance between predator and prey.  

 

     

Ladybird beetle larvae eats Mealybugs                              Ladybird beetle up to 4 mm long

 

Chemical Control

Spray with white oil may have an effect on the population or spray Omethoate. Contact insecticides are usually ineffective because of the insect's protective waxy coating.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

PEST

   NAME

     Two-spotted Mite, Red Spider Mite

     Tetranychus urticae

   ORDER

     Acarina

   FAMILY

     Tetranychidae

Description of the Pest

Also known as the red spider mite. Females are pale green or yellowish, depending on the host plant, and have two dark lateral markings; the mite becomes red in winter, retaining their dark markings. Nymphs are six-legged, with another pair of legs appearing as the mite matures. Males are smaller and narrower. Fully-grown adults are just visible to the naked eye. Two-spotted mites spread by crawling between nearby plants or movement of dead leaves.

Appearance and Distribution of the Pest

Found world-wide; an introduced pest in Australia. They congregate in protected places, such as under bark and at the base of trees, during winter. During spring, they become green in colour, and migrate back into the leaves. During heavy infestations, the leaves may be covered in visible webs, which they spin as they feed. Leaves may eventually wither and fall. Mites can spread via the movement of dead leaves, or in webs that have become attached to birds or large insects. They initially appear on the undersides of leaves.

Spruce Spider Mite (Oligonychus ununguis) is a tiny greenish black adult which lays eggs on twigs where they overwinter. The pale green young spiders suck the sap turning the leaves yellow to brown. Heavy infestations form webbing and the pest is found on Abies and Juniperus species.

Banana spider mite (Tetranychus lambi) is a major widespread pest of bananas.  It differs from two spotted mite by not producing copious amount of webbing.  It is highly active during the dry spring to summer period and with the onset of the wet season mite numbers are reduced.  The warm dry conditions that are created under plastic bunch covers is ideal for building up banana spider mite numbers.

Damage is normally confined to the underside of leaves appearing as rusty patches that coalesce along the leaf veins eventually turning the whole leaf brown-grey before it collapses.  Fruit is damaged, close to the bunch stalk causing the area to become dull red purple-black, which in turn becomes dry then cracks.

  Damage fruit

Control methods include careful water management during dry periods, and the reduction of dust from roadways.  Regular desuckering and leaf trimming of plants will assist with a good coverage when spraying miticides.

Life Cycle

Mites have a gradual metamorphosis, with several nymphal stages. Each female lays up to 100 eggs that hatch in 7-14 days, with several generations appearing throughout the year. Females may become inactive during cold weather.

Webbing         

Period of Activity

The Two-spotted mite is most active in hot dry conditions. Under optimum conditions, the population can double every four days. It produces large quantities of webbing for over-wintering nests. Many plants are only susceptible to this insect when cultivated under glass.

Damage Caused

Adults and nymphs lacerated the undersides of the leaves with there rasping mouth parts, although infestations on both surfaces are not uncommon. Infestations cause leaf mottling leaf fall; premature leaf loss causes loss of vigour and reduces the quality and quantity of future crops. Repeated infestations, year after year, may weaken root growth and kill herbaceous plants.

Susceptible Plants

A wide range of plants are attacked by the Red Spider Mite including annuals, fruit trees and vegetables, ornamental shrubs and trees.

Note

Many plant species are more susceptible to Red Spider Mite when they are cultivated under glass.

Other species of mite that are mentioned below have simular characteristics.

Calluna, Rose, Tropaeolum and Viola and species are infested with the Red Spider Mite (Tetranychus telarius) commonly in greenhouse situations.

Musa species are attacked by two spotted mite and banana spider mite damaging foliage and fruit.

Juglans species can be infested with up to four types of mites including red spider.

Cultural Control

Heavy rain or irrigation can reduce numbers; some plants may benefit from replanting in cooler locations. Generally, however, infested material should be completely removed and destroyed.

Preventative measures such as removing weeds or mulching around trees or shrubs or scrubbing the loose bark of susceptible trees during winter helps reduce numbers. During spring sticky bands can be wrapped around trunks close to the ground to trap the mites.

Biological Control

Natural predators include lacewings, ladybirds and thrips help keep the numbers down. Insecticide-resistant predatory mites (Typhlodromus occidenyalis) are also available commercially to control the Two-spotted Mite only on a large scale, as they require ample mites to survive.

Chemical Control

Spraying should be carried out as a last resort as many predators are killed during the operation and spraying can have the opposite effect by increasing numbers in the long term. Dimethoate will reduce numbers; however, Two-spotted mites are resistant to insecticides in some areas. Dusting with wettable sulphur may also prove effective.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

PEST

   NAME

     Cottonycushion Scale

     Icerya purchasi

   ORDER

     Hemiptera

   FAMILY

     Margarodidae

Description of the Pest

This pest is also known as Ribbed Scale or Bark-louse. The small soft bodied female is oval shaped, reddish-brown, and produces an extended fluted egg sack up to 10mm long that is covered with white, waxy threads. The crawlers are red with dark legs and the adult males are winged. The nymphs infest the ribs and veins of leaves, sucking the sap. Adults and nymphs suck sap with piercing and sucking mouth-parts and ants are attracted to the honeydew produced by feeding nymphs.

       Image by B. Sonsie

Appearance and Distribution of the Pest

This insect has a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.

Adults appear during the warmer months and infest twigs branches and are found on the trunks of some trees.  Ants will usually be present as feeding nymphs produce honeydew, as will the Verdalia ladybeetle, (Rodolia cardinalis), which feeds on the nymphs.

This Australian native insect has been introduced to many countries such as the USA, India, Egypt and South Africa and was only brought under control by the introduction of the Verdalia ladybeetle.

Period of Activity

There are usually two hatches each year, in early spring and late summer.

Susceptible Plants

There are many plants that are attacked by this insect including Australian native species such as Acacia, Eucalyptus, Pittosporum, Hakea and Grevilleas.

Ornamental trees and shrubs are also attacked including fruit trees and citrus, Liquidambar, Salix, Nerium, Magnolia, and Rosa species.

Palm such as Archontophoenix and Howea species are also attacked particularly when grown as an indoor or glasshouse specimen.

Damage Caused

Heavy infestations may cause die-back, particularly where natural predators are absent (eg in glass-houses). The excretion of honeydew promotes sooty mold that restricts the leaves capability to photosynthesize.

Cultural Control

Dead or damaged parts of the plant should be removed and destroyed including fallen fruit. Small infestations may be removed by hand or squashed on the stems. Healthy plants are less susceptible to attack, so maintain vigour of the plant and avoid using high-nitrogen fertiliser that produces excessive soft young growth.

When pruning susceptible plants paint the cuts with antifungal sealant paint as scale insects are attracted to the sweet smell of the sap. This will reduce the infection rate of the plant.

Biological Control

Natural predators such as parasitic wasps may reduce numbers of active nymphs; parasitic wasps are bred commercially in some areas for this purpose and the main natural predator is the Verdalia ladybeetle, (Rodolia cardinalis). It should be noted, however, that wasps would avoid dusty conditions.

Other predators that assist in control are assassin bugs, lacewings, hover flies and scale eating caterpillars. A variety of birds also attack scales.

Chemical Control

Normally not necessary.

PEST

 

   NAME

     Scale Insect

     Various Scale Species

 

   ORDER

     Hemiptera

 

Description of the Pest

Generally scales are soft bodied insects that have a hard (armoured) or soft covering to hide under. They have piercing and sucking mouth parts that are attached to the host, feed off sap and soft scales commonly producing sweet honeydew, which in turn attracts sooty mould and ants.

The adult female has a circular or oval covering depending on the species and is up to 8mm across. The first stage (crawlers) hatch and wander around the leaf surface until finding a suitable place to suck sap, normally in colonies and the smaller male is relatively inconspicuous.

 

Hard Scale                   Soft Scale, attending Ants

 

Cactus Scale (Diaspis echinocacti) has a circular greyish female and a narrow white male scale and is commonly found on house plants.

 

Chain Scales (Pulvinaria species) adult females are obvious with large group of eggs that are white or cottony-like, and the tiny young light green scales are flat and oval-shaped up to 2mm long. The legged nymphs are normally arranged from head to tail along the mid rib of the leaf, and may move to a new position to feed. They excrete honeydew and attract sooty mould and are found on Acacia and Acronychia species.

 

Chinese Wax Scale

 

Chinese Wax Scale (Ceroplastes sinensis) is a domed wax scale that has dark spots around its margin and immature scales form waxy material around there margins.

 

Fern Scale on Aspidistra elatior

 

Fern Scale or Coconut Scale (Pinnaspis aspidistrae) appears as flecks up to 0.15mm long with a white covering over the male congregating on the underside of the fronds on the axils and among the sporangia causing them to turn yellow. Many species of fern are susceptible to infestation.

 

                  Flat Brown Scale

 

Flat Brown Scale (Eucalymnatus tessellates) are light brown up to 0.5mm long, flat and closely attached both sides of the leaf and causing yellowing of the foliage.

 

Juniper Scale (Diaspis carueli) is tiny and circular, white maturing to grey-black and as it feeds the needles turn yellow and die.

 

Oleander Scale (Aspidiotus hederae) is a pale yellow circular scale up to 3mm across and is found in dense colonies on the stem or leaves.

 

Tea-tree Scale (Eriococcus orariensis) are a creamy blue colour normally packed along the branches and are plump and rounded to 4mm across.

 

                  Wattle Tick Scale

 

Tick or Wattle Scale (Cryptes baccatus) adult is domed, blue-slate colour with a leathery covering up to 10mm long. All stages of growth are found in groups of over forty, packed along the stems and normally tended by ants as they produce large amounts of honeydew. A serious pest of Acacia species found inland or coastal from temperate to sub tropical climates and commonly accompanied by Sooty Mould.

 

Toxic Scale (Hemiberlesia lataniae) is a tiny flat rounded scale up to 0.15mm long and is white to pale pink. It is normally found in colonies on the small branches and twigs of shrubs. It injects a toxic substance into the host as it sucks sap causing the death of the branch.

 

Wattle Scale (Pseudococcus albizziae) is soft, plump and secrets cotton-like threads. It is not a true scale insect and is simular to mealy bugs. It is reddish-brown up to 0.4mm long and secrets large amounts of honeydew as it sucks sap in colonies along the branches.

 

Life Cycle

These insects have a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.

 

Appearance of the Pest

All parts of the plant above the soil may be attacked, but normally the stems and leaves and scale tends to favour well-lit positions.

 

Period of Activity

The nymphs and females are active for most of the year, in warm climates. Once they selected a position they attach and don't move. Normally the winged or wingless males are mobile and only soft scales produce honeydew.

 

Susceptible Plants

There is a wide range of susceptible plants including citrus, willows, holly, and many ornamentals, such as roses or Paeonia species. It also attacks indoor or glasshouse plants and Australian native plants such as wattles, hakeas, grevilleas and eucalyptus.

 

Acacia species are attacked by the Tick or Wattle Scale, which infest twigs and small branches and heavy infestations will kill the host plant.

 

Acer species are attacked by the Cotton Maple Scale (Pulvinaria innumerabilia) which prefers Acer saccharinum. Nymphs first attack the leaves and the brown adult scale is covered in a woolly mass up to 14mm across, normally found on the underside of the stems and twigs.

 

Acmena smithii, Melaleuca, Syzygium and Pittosporum species are attacked by the Chinese Wax Scale.

 

Aesculus species are attacked by several scale insects including the Walnut Scale (Aspidiotus juglans-regiae) which is saucer-shaped and attacks the main trunks.

 

Agave species are susceptible to several types of scale including (Aspidiotus nerii), (Aonidiella aurantii) and (Pinnaspis strachani), but generally do not require control.

 

Asplenium australasicum

 

Asplenium australasicum is susceptible to Coconut Scale or Fern Scale (Pinnaspis aspidistrae). It is normally found on the under side of the fronds. Small infestations cause little damage.

 

Bougainvillea species may be attacked by the soft scale (Coccus hesperidum) outdoors or under glass.

 

Calluna and Vaccinium species are attacked by the Oyster Shell Scale (Lepidosaphes ulmi).

 

Camellia species may be attacked by the Florida Red Scale (Chrysomphalus aonidum), which is small, circular and black and is found firmly attached to the underside of the leaf along the veins. On inspection after removing the scale the insect has a pale yellow body. Camellias are also attacked by a large variety of scale insects including Tea Scale and Camellia Scale.

 

Carpinus species may be attacked by the scale (Phenacoccus acericola). It is found on the underside of the leaves forming a white cotton-like clump along the veins.

 

Casuarina and Allocasuarina species may be attacked by the Casuarina Scale (Frenchia casuarinae), a black hard scale that is upright to 4mm with a pinkish body. During attachment the surrounding tissue swells up and in time can, form galls. This weakens the wood and in severe infestations may kill the tree.

 

Cotoneaster species are attacked by up to four species of scale including the Oyster Shell Scale (Lepidosaphes ulmi).

 

Cupressus species are attacked by Bark Scale (Ehrhornia cupressi) is pink and covered in white wax. Heavy infestations cause the leaves to turn yellow or reddish.

 

Flat Brown Scale on Cycas revoluta

 

Cycads, palms and some species of Callistemon are attacked by the Flat Brown Scale.

 

Erica species are attacked by several species of scale including, Greedy, Oleander and Oystershell scale.

 

Jasminum species can be infested with up to twelve types of scale.

 

Juniperus x media and other conifer species are attacked by the Juniper Scale.

 

Leptospermum species are attacked by the Tea-tree Scale which produces ample honey dew that promotes sooty mould.

 

Palm and Fern species are susceptible to attack by the Coconut Scale or Fern Scale (Pinnaspis aspidistrae) which infests the underside of the leaves. They are also hosts for many other scale species such as red, cottony cushion and tea scale.

 

Pinus species are attacked by several species of scale including the Pine Tortoise Scale (Toumeyella numismaticum) and the Red Pine Scale (Matsucoccus resinosae).

 

Polygonum odoratum is attacked by a small brown scale.

 

 

Sorbus aucuparia is attacked by a five species of scale insect, including Black Cottony Maple, San Jose and Scurfy. Generally they suck on the sap of the new growth and leaves.

 

Strelitzia species are attacked by the Greedy Scale (Aspidiotus camelliae).

 

Damage Caused

Leaves become yellow and are shed prematurely and there may be twig or stem die-back. When the infestation occurs on fruit, the fruit is small and its skin becomes pitted and cracked. Small trees and saplings that are heavily infested may be seriously damaged or die. Sooty mould can cover fruit or leaves causing a secondary problem.

 

Cactus Scale can completely cover the host cactus sucking sap and causing it to die.

 

Cultural Control

Dead or damaged parts of the plant should be removed and destroyed including fallen fruit. Small infestations may be removed by hand or squashed on the stems. Healthy plants are less susceptible to attack, so maintain vigour of the plant and avoid using high-nitrogen fertiliser that produces excessive soft young growth.

When pruning susceptible plants paint the cuts with antifungal sealant paint as scale insects are attracted to the sweet smell of the sap. This will reduce the infection rate of the plant.

 

Biological Control

Natural predators such as parasitic wasps may reduce numbers of active nymphs; parasitic wasps are bred commercially in some areas for this purpose. It should be noted, however, that wasps would avoid dusty conditions.

Other predators that assist in control are assassin bugs, ladybirds, lacewings, hover flies and scale eating caterpillars. A variety of birds also attack scales.

The control of ants that transport aphid from one host to another also reduces infestation and can be carried out by applying at least three greased bandages 5mm apart around the stem or trunk of the plant.

 

Chemical Control

Spray the entire plant with dilute white oil solution; a follow-up spray may be required after four weeks, for heavy infestations. Spraying of chemicals will also kill of natural predators and in some cases the secondary scale infestation is more prolific especially when using copper based chemicals.

Some chemical controls, such as methidathion, are available - please seek advice from your local nursery as to the suitable product for your area.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

Note: Plants affected by this pest are Deer Resistant plants not the susceptible plants.

 

PEST

   NAME

     Deer

     Cervus species

   ORDER

     Artiodactyla

   FAMILY

     Cervidae

 

 

Description of the Pest

There are two species of the deer in North America, the Whitetail (Odocoileus virginianus) and the Mule deer (Odocoileus hemionus) with several regional variations such as the Pacific coastal Blacktail (O.h. columbianus) which is regarded as a sub-species of the Mule deer.

 

The Whitetail on average grows to 112 cm (44in) tall and 180 mm (70 in) long and weigh 68 kgs (150lbs). The fir colour varies according to its environment but generally it is reddish-brown during summer and grey-brown in winter with a pure white underside on its tail. When the tail is erect it is known as the "white flag". Its antlers consist of two main beams from which the points emerge.

 

The Mule deer grow to 105 cm (42 in) tall and are up to 200 cm (80 in) long with the adult buck weighing up to 137 kgs (300 lbs) and the does up to 80 kgs (175 lbs). The fir is generally tawny brown during summer and during winter it has a heaver grey-brown to blue-grey coat with a small white tail that is tipped in black. The other distinguishing features are its ears that are up to 300 mm (1 ft) long (mule-like) and its antlers, with the two beams that are forked into smaller beams, which inturn fork again and again.

 

The Blacktail deer (Pacific coastal Blacktail) grows to 97 cm (38 in) tall and is up to 105 cm (60 in) long and weighs on average 73 kgs (160 lbs). The fir is generally tawny brown during summer and during winter it has a heaver grey-brown to blue-grey coat with a tail that is dark brown at the base then changing to black for 50% of its length. The antlers consist of two beams that are forked into smaller beams, which inturn fork again and again.

 

Appearance and Distribution of the Pest

The Whitetail deer are found throughout eastern United States, on the coast and inland but are not commonly seen in California, Utah or Nevada. They do not migrate but congregate together (yard up) during winter and feed in a part of their existing territory.

 

The Mule Deer are found in the western part of North America from South eastern Alaska to Mexico and from the Pacific coast to Texas. They migrate from highland mountain meadows to southern or lower snow free forested valleys during winter.

 

The Blacktail deer are found on the Pacific coast from Alaska to northern California. There is both resident and migratory Blacktails. The  migratory Blacktails move southwards during late autumn at the first sigh of snow or heavy sustained rain and the resident Blacktails seek cover their existing territory amongst woodlands during the winter months.  

 

Life Cycle

All Deer breed from autumn to early winter and the does give birth from late spring to early summer.

 

Period of Activity

Deer are most active from spring to autumn but can be troublesome during winter when the feed is scarce. In some regions urban landscapes become the major food source both in summer and winter.

 

Damage Caused

Browsing deer will feed on almost any plant and is most commonly noticeable during spring feeding on the new growth or twigs and stems leaving a shredded appearance. Deer also rub their antlers against trees damaging bark and snapping off small branches, this action also incurs damage under hoof as plants, lawns and garden structures are trampled on.

 

Susceptible Plants

Some plants are more palatable to deer but when a deer is hungry or during drought conditions there are no "Deer Proof" plants. There is a range of plants that have a bad taste and are not destroyed and are regarded as (deer resistant plants). Deer resistant plants are the plants that are attached to this file not the susceptible plants.

 

Cultural Control

There are many cultural controls that have been tried to move browsing deer such as frightening them with strobe lights, pyrotechnics or tethered savage dogs. These actions are only temporary and may cause more trouble as the stampeding animals move off. Fencing and netting can be an effective method of discouraging hungry deer from gardens but may be expensive on a large scale and require maintenance. There are several types of fences which include conventional 2.2m (8 ft) deer-proof woven wire fences or single-wire electric fences and slanted deer fences. Plant selection can also be effective, by using less desirable plants (deer resistant plants) as an outer border to the more desirable plant species and  thus discouraging the deer to enter the garden. Hedges and windrows of less desirable thorny plants can also be a deterrent to browsing deer.

 

Chemical Control

There are two main types of repellents contact and area. Contact repellents are applied directly to the plants and deter deer with a bad taste or smell. They can be applied by rubbing or spraying on to the plants and commonly used in an egg mixture. The commercial products have proven to work better than home remedies which include soap or chilli mixtures and hanging bags of human hair.

Area repellents rely on an offensive odour and are placed around areas that are frequently visited.

 

Contact your local distributor for available types and application.

DISEASE

   NAME

     Bacterial Rot

     Various Bacterial Species

Description

Bacterial problem associated with water soaked strips on the leaves, stem, roots, fruit or flower. Bacterial wilts produce causative slime that clogs the water-conductive tissue of a plant.

Symptoms

Bacterial Blight (Pseudomonas mori) forms water soaked spots on the leaves and shoots, becoming sunken and turning black causing the leaves and twigs to wilt and die.

There is also a Bacterial Blight (Pseudomonas syringae pv pisi) that infects legumes during humid weather with water soaked spots on the leaves and stems near the base. The spots become dark and as the stem shrivels, yellow lesions appear. Leaves and fruit pods turn brown and die.

Bacterial Leaf Spot (Pseudomonas viburni) forms wet spots that enlarge becoming brown and sunken. These spots can be seen on the leaves and young stems and the bacteria overwinter in buds or in cankers. It is found on Viburnum species.

Bacterial Wilt (Xanthomonas species) infects palms causing the lower fronds to wilt then turn grey-brown and die. This is followed by the crown becoming spongy (rotted) attacking the vascular tissues and eventually causing the collapse of the crown. There is also a Bacterial Leaf Spot (Xanthomonas species) that causes spots on leaves with water-soaked margins and is found on Alocasia species.

Bacterial Wilt

Bacterial Wilt (Pseudomonas solancearum biovar 1 and 3). This disease initially turns the youngest leaves pail-green to yellow; they then wilt turn brown and die. It eventually affects the entire plant and is found on Heliconia species.

                  Black Rot or Bacterial Wilt

Black Rot or Bacterial Wilt (Xanthomonas campestris) is a bacteria rot that infects the leaves and seedlings of Cruciferous vegetables causing 'V' shaped pale yellow blotches to appear, normally infection occurs along the margin of the leaf or through damaged areas of the leaf. It also causes the flower head to become stunted and the veins or water conducting tubes in the leaves and stems to turn brown or blackish. Heavy infections cause the plant to wilt and die.

Bud Rot (Xanthomonas cannae) infects young leaves and flower buds of Canna species, killing them. Small whitish spots appear as the leaves or buds open, these enlarge then run together turning black. The symptoms also extend to the petioles and stems forming yellowish water soaked areas and the bacterium overwinters in the rhizomes.

Halo Blight of Beans (Pseudomonas syringae pv phaseolicola) forms water soaked or greasy angular spots on the pods or stems of the host. This causes the plants to yellow and become stunted. During humid weather a white slime is exuded from the damaged areas.

Soft Rot (Pecotbacterium carotovorum) affects bulbs, initially stops flowers from blooming or forming correctly. These flowers are shed, and the plant rots at the base causing it to collapse. On inspection of the bulbs a white foul smelling viscous smell is associated with a soft rot.

Wetwood (Erwinia nimipressuralis) causes wilting and branch dieback in Ulmus species. The wood forms dark water soaked areas with no obvious streaking in the outer sapwood.

Yellow Rot in Iris

Yellow Rot (Xanthomonas hyacinthi) is a bacterial disease infects the cell walls of the leaf, stem and bulbs and caused yellowish water soaked areas to appear. These areas become brown and shrivel, or pockets of rot appear, soon engulfing the entire bulb. The disease may start from the leaf down or from the bulb up infecting the whole plant. A cross section reveals vascular tissue that is choked with yellowish slime. Infected plants soon brown off, collapse and die.

Source and Dispersal

The bacterium is found in infected plant material and not necessarily the soil and is spread by splashing water, wind or infected stock.

Favoured Conditions

It prefers warm moist conditions normally during spring.

        

Affected Plants

These bacteria attack many plants including; onions, Hyacinth species and its varieties, this can be a major problem in bulb nurseries.

Vegetables such as potatoes are also infected by blight which forms dark brownish spots on the leaves that become larger, eventually killing them and followed by lesions on the stems. The roots are infected by falling spores and peas suffer from a bacterial blight that forms spongy leaves with dark brown edges. The leaves and stem shrivel and die.

Strelitzia nicolai

Archontophoenix and Strelitzia species are susceptible to the Bacterial Wilt (Pseudomonas solanacearum). The leaves become yellowish and brownish along the margins causes the fronds to wilt and dry out. The vascular tissue in the stems then becomes blackish and the plant dies prematurely.

Berberis species are infected by the Bacterial Leaf Spot (Pseudomonas berberidis) forming irregular dark green water soaked areas that turn purplish brown. It also infects young shoots and petioles or damaged areas.

Bougainvillea and Limonium species are infected by the Bacterial Leaf Spot (Pseudomonas andropogonis) which forms orange angular spots that are lighter in the centre and cause the leaves to fall prematurely. It is most common in tropical regions.

Caryota mitis (Clumping Fish Tail Palm) is infected by the Bacterial Blight (Pseudomonas avenea). The symptoms include water soaked translucent areas along the leaf veins that mature to brown then black with a chlorotic halo that is up to 2 mm wide by 50 mm long.  Leaves of all ages are infected and immature leaves are more severely infected.

Control methods include eliminating overhead watering, removing infected foliage and improve air circulation around the plant.

Caryota mitis

Cheiranthus species and other plants in the Brassicaceae family are infected by the Bacterial Wilt (Xanthomonas campertris) causing the leaves to wilt, turn yellow and die. It also stunts the inflorescence and turns the phloem and xylem blackish. Other plants that are infected include, Arabis, Armoracia, Aubrieta, Brassica, Hesperis, Iberis, Lobularia and Mathiola species.

Corylus species are infected by Blight ((Xanthomonas corylina) that attacks the leaves and branches.

Delphinium species are infected by several leaf spots including the bacterial disease Black Leaf Spot (Pseudomonas delphinii) which produces irregular tar-like spots on the upper surface of the leaf with corresponding brownish areas on the underside. This infection may extent down the petiole to the twigs. It normally occurs during cool weather affecting the lower leaves first.

Dianthus species are infected by the Bacterial Wilt (Pseudomonas caryophylli) which turns the leaves greyish, then yellowish before dieing. Yellowish streaks are also seen on the stems.

Dieffenbachia species are infected by two Bacterial Leaf Spots (Erwinia species) and (Xanthomonas campestris pv. dieffenbachiae). Both form yellowish spots that turn brown on the leaves that have water-soaked margins.

Eschscholtzia species are infected bt the Bacterial Blight (Xanthomonas papavericola) which forms tiny black spots that are water soaked and may be ringed.

Euphorbia pulcherrima is infected by Bacterial Canker (Corynebacterium poinsettiae) which forms streaks on the green stems that are water-soaked. The leaves may also be affected producing spots or blotches.

Gladiolus, Crocus and Freesia species are susceptible to Bacterial Scab (Pseudomonas marginata). This disease attacks the corms by forming slightly raised yellowish lesions that develops a raised rim with a soft sunken centre, producing bacterial exudate. It also infects the leaves with small reddish spots appearing towards the lower part. These spots merge and destroy the basic cell structure (parenchyma tissue) in the petioles causing the leaves to fold downwards, eventually killing the plant.

Hedera helix is susceptible to the Bacterial Leaf Spot or Stem Canker (Xanthomonas hederae). This infection commences with pale green water soaked spots or areas appearing on the leaves. These areas than become brown-black and dry with reddish margins, eventually engulfing the leaf causing it to shrivel. The bacterium then extends along the twigs and into the stems causing cankers. Several Fungal leaf spots develop simular symptoms and may be difficult to distinguish the difference. Generally avoid high humid temperatures and water plants at the base.

          Hedera helix

Morus species are infected by Bacterial Blight (Pseudomonas mori).

Orchids such as Cattleya, Cymbidium, Cypripedium, Dendrobium, Epidendrum, Oncidium, Paphiopedilum, Phalaenopsis and Zygopetalum species are infected by Bacterial Brown Rot (Pseudomonas cattleya) which forms water-soaked leaf spots that turn brown. Phalaenopsis species are particularly susceptible.

Caryota species are susceptible to Bacterial Leaf Blight (Pseudomonas albopercipitans). This disease forms elongated water soaked areas on the fronds that are translucent at first becoming blackish.  

Roystonea regia, Cocos nucifera and Phaseolus  species are infected by Bacterial Wilt (Xanthomonas species).

Tropaeolum species are infected by Bacterial Leaf Spot (Pseudomonas aptata) forming spots and rotting the leaves. They are also infected by the Bacterial Wilt (Pseudomonas solanacearum) which gains access through damaged roots or through the stomates, causing yellowing, wilting and the death of the plant.

Zinnia species are attacked by Bacterial Wilt (Pseudomonas solanacearum).

Non-chemical Control

Remove and destroy any infected plants. As a preventive measure cultivate the surrounding soil to improve drainage, aeration and minimise weed growth. Do not over water and allow the soil surface to dry before rewatering. When handling the plants pick a dry period and take care to minimise damage.

At first sigh of infection the plant should be removed and disposed off and avoid replanting susceptible vegetables such as peas for up to three years.

Chemical Control

There is no satisfactory chemical control. It is important to take preventive measures.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

DISEASE

   NAME

     Crown Gall

     Agrobacterium and other species

Description

Bacterial problem that is associated with wounds, caused by insects or physical damage in plant tissues.

Symptoms

Soft galls appear on the roots, base and up the stem becoming hard with age. The plant responds by loosing vigour and may produce less flowers or fruit.

Source and Dispersal

The spores are found in the soil or are released from decaying galls and are spread by infested soil or plant material and contaminated tools.

Favoured Conditions

Continuous cultivation of infested plants allowing a build up of spores in the soil and poor propagation methods during grafting or handling transmits the disease.

        

Affected Plants

There are many species of woody plants that are affected these include, species in the Rosaceae family, Dahlias, Geraniums, Vitis and Brachychiton species.

Araucaria, Arbutus, Begonia, Chaenomeles, Corylus, Euonymus, Euphorbia, Leucanthemum, Protasparagus, Thunbergia and Wisteria species are infected by a simular crown-gall (Erwinia tumefaciens) which causes smooth swellings to appear on the roots and main stems of the host.

Large cactus species are attacked by the Crown Gall (Agrobacterium tumefaciens). It develops galls on segments and roots with some of the aerial galls attaining a diameter of over 600 mm.  Root galls, become a spongy and may attain a diameter of 300 mm. Galls on aerial parts may be cut from the plant with some success. Control methods include not damaging the plant surface and any bacteria contaminated soil should not be used for propagation.

Sorbus aucuparia is seriously affected by this disease.

Non-chemical Control

Remove and destroy any infected plants and avoid replanting in the same area with susceptible species. Care should also be taken when selecting new plants that they are not infected, look for lumps at the base of the plant. Disinfect pruning or grafting tools to inhibit transmitting the disease.

A treatment of control is to dip seeds, cuttings and seedlings into a solution of a non-pathogenic strain of bacteria such as Agrobacterium rhizogenes before planting. This is commercially available under several brand names.

Chemical Control

There is no chemical control of this bacterial problem.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

DISEASE

   NAME

     Grey Mould

     Botrytis cinerea, B. elliptica

Description

Grey Mold, Shoot Blight, Petal Blight is a fungus problem that generally forms water-soaked spots that rot and produces greyish sclerotia (fungal resting bodies) on the surface. They can be found throughout the year on dead tissue and on live material during under ideal climatic conditions. Damaged areas such as a tear in a leaf or an opening made by an insect are more likely to be infected.

Grey Mold on Begonia species

Image by B. Sonsie

Symptoms

The fungus attacks stems, leaves, flowers and fruit. In roses the fungus is primarily attacks the flowers producing pink rings on the petals and buds that become brown and rotten. This may extend down the peduncle to the stems causing dieback.

In other plants oval yellowish to brown spots appear, then the centre turns greyish and dries out and in humid weather the spots spread, joining up and infecting the entire leaf. This infection may also occur on the stems, and flowers may form abnormally or brown off and die.

When lettuce is infected it starts at the base causing a soft brown rot that may extend up the stem killing the plant, and pears flowers become infected then spreading to the fruit. This develops a sunken brown area that is soft and eventually is covered in grey powdery spores.  

                  Botrytis Blight on Senecio cruentus

Botrytis Blight (Botrytis tulipae) infects leaves, flowers and stems with flecks of brown spots that merge to form light grey rotted areas that have brownish margin that may destroy stems. Affected areas are covered in a grey mould during humid conditions. The spores overwinter in dark brown sclerotia, which are found on the outer scales of the bulb or at the base of the stem in Tulipa species.

Grey Bulb Rot (Rhizoctonia tuliparum), which infects the bulbs of Tulipa species, attacking the base of the leaves and rotting the bulb. When bulbs emerge during spring in infected soil's they soon die off. The greyish mold tends to be dry.

Source and Dispersal

The sclerotia (fungal resting bodies) are found on dead plant material or in the soil and remain viable for many years. The spores are dispersed by wind or splashing water.

Favoured Conditions

It prefers cool moist climate with morning dew.

Affected Plants

Grey Mold attacks a wide range of plants including roses, fruit trees, pelargonium, ferns, grapes and cyclamens. Heliotropium , Amaryllis, Lilium and Hippeastrum species  are also infected.

Agave species are infected by two fungal Leaf Blights (Botrytis cinerea) and (Stagonospora gigantea) that severely damage the leaves particular during wet periods or from excessive watering.

Cactus species are infected by soft rot or Grey Mould (Botrytis cinerea). Stems and pads turn are greyish with the upper surface, rotting then collapsing.  The dieing tissue becomes slimy and is covered with grey mould that develops black sclerotia, which propagates the disease.  It is more prevalent under warm humid conditions and control methods include removing infected parts and destroying them.  In glasshouse situations ventilation should be improved and watering should be restricted to create a drier atmosphere.

Cereus species and other cacti are infected by Grey Mold causing the segments to become discoloured and as the rot progresses it tissue becomes slimy and collapses. Black sclerotia forms on the affected areas that are covered in grey mold during humid conditions.

Cuphea species are infected by this blight.

Orchids such as Cattleya, Cymbidium, Cypripedium, Dendrobium, Epidendrum, Oncidium, Paphiopedilum, Phalaenopsis and Zygopetalum species are infected by Grey Mold or Petal Spot (Botrytis cinerea). Petal and flower stalks form small brown spots.

Paeonia species are infected by Botrytis Blight (Botrytis paeoniae) causing the leaves and flowers to form a grey mold then suddenly collapse and die.

Pseudotsuga menziesii   Douglas Fir is infected by Leaf and Twig Blight (Botrytis cinerea). This is a serious problem in wet conditions and is difficult to control.

Ribes species are attacked by Cain Blight (Botryosphaeria dothidea). The infection causes the cains to become blighted and wilt. To control remove damaged wood and destroy.

Non-chemical Control

Remove and destroy infected plants or fallen leaves. When planting, space as to allow good air movement to reduce humidity. Bulbs that are infected should be discarded and take care that bulb scales are removed from the soil to prevent further infection. Cactus and succulents that are infected should have the damaged areas cut out, or discard the entire plant. Under glasshouse conditions improve the ventilation and reduce watering to create a drier atmosphere.

Chemical Control

Under humid conditions spray regularly using a suitable fungicide such as thiram, mancozeb, dichloran and chlorothalonil.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

DISEASE

   NAME

     Fungi (General)

     Various Fungal species

Description

A fungus is a plant that lacks chlorophyll and conductive tissue. Generally they are made up of branched threads called 'hyphae' and collectively form a vegetative body called 'mycelium'. The fungus is small but the fruiting bodies can become very large up to 600mm across such as bracket fungi or mushrooms. Common fungi are mould and mildews. problem that attacks the roots causing them to rot.

Fungus can reproduce many ways but primarily it is asexually, simular to cuttings of a plant and often occurs with minute portions of the mycelium (spores) separating. The spores can be arranged in a structure such as a sporangia or pycnidia or develop without an enclosed structure called a "conidia". Either way the fungus propagates very rapidly.  Sexually reproduction occurs when two nuclei unite and form sexual fruiting bodies (zygospore).

Strelitzia reginae flower

Symptoms

Fungus attacks all the above or below ground level parts of the plant living within the tissue of the plant and are very small and not normally detected until the fruiting body appears. However parasitic types such as powdery mildew or rust are visible on the outer surface of the plant.

Fungi hyphae may be divided by cross walls and known as "septate" while others with no cross walls are known as "nonseptate". These are the fungi responsible for cell leakage as in rot.

Back Mold (Chalariopsis thielavioides) affects understocks of grafted Rosa species by inhibiting the development of callus. It is whitish-grey maturing to black and can be found in the pith of the rose stem.

Black Root Rot (Chalara elegans).This recently introduced fungal disease in Australia (1993) affect plants by blackening the root systems and turning leaves yellow or purple. It is difficult to identify specifically as other pathogenic root diseases and nutritional deficiencies have simular characteristics.  

The asexual spores are dispersed by wind or water. It is also transmitted on insects and in contaminated growing media or plants preferring humid moist conditions.

This fungus affects a wide range of ornamental plants including; annuals, perennials and shrubs. Examples are Begonia, Boronia, Camellia, Cyclamen, Fuchsia, Gerbera, Grevillea, Impatiens, Pansy, Petunia, Rosa species and Snapdragon.

Black Stem Rot (Pythium splendens) normally is a rot that occurs in cuttings turning the stem progressively black and shrunken. The leaves fall and the plant becomes stunted, eventually dieing.

Bleeding Necrosis (Botyosphaeria ribis) attacks and kills the inner wood causing the bark to split open and bleed sap giving it an oily appearance.

Blight (Endothia parasitica) is a serious pest of Castanea species, entering the twigs and small branches, and then progressively travelling throughout the tree killing it. It may form cankers on the base of the trunk or in the dead branches above with the amber coloured fruiting bodies pushing there way through the bark.

Copper Web ((Rhizoctonia crocorum). This fungal disease appears in defined patches causing the corms in the centre to become a black powdery mass. Corms on the outer ring of the patch that are partially infected forming a felty mass of violet threads on the corm scales. These threads extend into the soil and large sclerotia forms in the soil and on the corms. Healthy corms become infected from contaminated soil that contains mycelium and sclerotia.

Dry Rot (Phyllosticta concave) forms small circular spots that increase to a diameter of 30mm, and then becomes sunken as the cells collapse. The infected area develops minute black fruiting bodies.

Dutch Elm Disease (Ceratocystis ulmi) is a serious fungal problem of Ulmus species that initially causes yellowing then wilting of the leaves that turn brown and die. This may be seen on certain branches of the tree and on inspection under the bark the sapwood reveals brown streaks. A cross section of the affected branch displays round spots that are dark brown. This infection normally spreads quickly throughout, killing the tree in one to two seasons.

Dieback in Camellia (Glomerella cingulate) is a pathogenic fungus that infecting existing wounds such as leaf scars or mechanical damage, forming a sunken area (canker) that spreads around the stem causing die back. The affected plant has new shoots that are brown-black and the tips curl, forming a 'Shepard's Crook' appearance. The leaves also die but are persistent on the plant and the spores are found in soil or on other infected plants.

Curvularia Leaf Spot (Curvularia species) in Turf Grass. This is normally a secondary weak fungal infection that forms spots on the leaves that lengthens turning the leaves greyish. The leaf shrivels then dies and infected areas appear as weak patches in the turf. Preventive measures include minimising leaf wetness and excessive use of nitrogen fertiliser.

Fairy Rings Blue Couch     

Fairy Rings are a fungal problem in Turf Grass and is caused by several species including (Lycoperdon species), (Marasmius species) and (Tricholoma species). Rings appear in the turf as fruiting bodies or dead grass and as lush green foliage. The mycelia expand radially in the turf feeding on soil nutrients and organic matter with water present.

Under severs conditions the mycelia consume all available nutrients resulting in the death of the turf. Lush turf can result from a less developed infection, where the decomposing hyphal releases nitrogen. This available nitrogen may be beneficial to the turf but some forms of nitrogen are detrimental.

Leaf Blister (Taphrina coerulescens) appears as yellowish circular raised areas on the upper side and depressions on the underside of leaves, up to 15mm across. As the fungus spreads the leaf dies but remains attached to the tree and this infection is commonly found on Quercus species..

Leaf Blotch (Guignardia aesculi) forms small or large water soaked spots that are reddish with a bright yellow margin and form black fruiting bodies in the centre. The affected leaf and petiole have a scorched appearance before falling, found on Aesculus species

Grevillea robusta     Leaf Scorch

Leaf Scorch (Verrucispora proteacearum) is a fungal disease that infects leaves causing large parts of the leaf to turn grey-brown, giving the appearance that it has been singed by fire. Black fruiting bodies appear on the affected areas and the leaf soon withers then dies. New, mature leaves are affected during very wet periods towards the end of the branches and Grevillea and Hakea species are susceptible.

Melting Out (Helminthosporium vegans) forms bluish black spots with straw coloured centres on the leaves and may be found on the sheath, encircling it causing Foot Rot. It infects grasses particularly Poa pratensis. There is another fungus that is simular Helminthosporium Blight (Helminthosporium dictyoides) that infects Poa, Festuca and Agrostis species.

Pad decay (Aspergilus alliaceus) infects Cereus and Opuntia species and occurs at during periods of high temperature.  The yellow spores at the epidermal layer through wounds and germinate on mass causing the area to become soft and spongy. An anthracnose called Shot Hole is a similar forming brownish spots the turn grey, and then black destroying pads. Control methods include physically removing damaged pads and allowing the Sun to heal wounds.

Potato Gangrene (Phoma foveate) is a soil borne fungus that infects the roots during harvest primarly through wounds and develops during storage. The potatoes rot from the inside forming rounded depressions on the surface and have a strong odour of rotten fish.

Root Rot Fungi (Phymatotrichum omnivorum) and (Pellicularia filamentosa) cause the roots to rot and the plant suddenly wilts then dies.

Root Rot (Pythium debaryanum) forms water soaked dark brown streaks that affect all parts of the plant causing wilting then dieing. It infects Ranunculus species, it also infects cactus species by forming brown spotting and wilting that appears at the base of the plant then extends towards the top. It quickly spreads from plant to plant in collections and is controlled by avoiding over watering, excessive humidity and are using a sterilised soil when potting up.

This fungus also is responsible for damping off of seedlings in a glasshouse environment.

Spring Dead Spot     

Spring Dead Spot (Leptosphaeri species) is a fungal disease that infects Couch Grass. It first appears during autumn as pale bleaches areas up to 500mm (20in) wide and persists throughout winter. In spring the affected areas do not recover or recover slowly and on inspection the roots or rhizomes are rotted. Runners from the surrounding healthy turf will help with recovery and all signs of the problem disappear by mid summer.

Cactus species      Pachypodium species

Stem Rot (Helminthosporium cactivorum) forms well defined yellow lesions that mature into soft dark brown rot. It commonly infects Cactus species entering through the stomates or wounds. Heavily infected plants collapse and die.

Stem Rot or Basal Rot (Pellicularia rolfsii) is a soil borne fungus that infects the stem root junction and extends into the leaves. In orchids the leaves become discoloured, dry and detach from the base which is covered in a fungal growth that produces sclerotia. The sclerotia is whitish to yellow then becoming dark brown and can be viable for up to four years.

White Mold  (Ramularia desta f. odorati) occurs on both sides of the leaf and looks simular to powdery mildew but forms faint dull, reddish brown elongated spots on the leaf that may be depressed or along the margin where they have a watery appearance. Tufts of hyphae develop in the stomates.

Wilt (Ceratocystis fagacearum) causes leaves to curl then turn brown and the sap wood may also turn brown or black. Heavy infection may kill a tree within two seasons and is found on Quercus species and other ornamental trees.

Witches Broom may be a fungal problem that causes a proliferation of small axillary shoots to appear at the end of the branches. Little is known about this problem, though it affects a wide range of plants including Eucalyptus, Leptospermum and Pinus species.

Source and Dispersal

Fungus is found in the soil or on other infected plants and after releasing the spores, they are dispersed by wind or are transmitted in infected stock, insects and with splashing water.

Wilt is transmitted by infected root stocks, several species of insect and contaminated tools.

Dutch Elm Disease is transmitted by bark beetles such as (Scolytus multistriatus) and (Hylurgopinus rufipes). These beetles deposit eggs in the sapwood where the lava tunnel and pupate. The emerging beetles tunnel the bark and carry the fungus to fresh feeding sites on the tree. Infected beetles may also be transported to fresh sites in waist material.

Favoured Conditions

Prefers cool moist conditions with temperatures from 10º to 25ºC and is more common from autumn to spring when it is wet.    

        

Affected Plants

A wide range of plants and all parts can be infected by various fungal diseases. Bleeding Necrosis is found in Liquidambar species and Stem Rot or Dry Rot infects Cactus species such as Opuntia and Pelargonium.

Abies species are infected by several fungi that cause Leaf Cast which turn the needles yellow to brown then fall prematurely.

Abutilon species are infected by the Stem Rot (Macrophomina phaseolin) affecting the lower stems and is not commonly seen.

Achillea, Cuphea, Leucanthemum, Euphorbia species are infected by the Stem Rot (Pellicularia filamentosa) which enters through the roots and rots the base of the stem.

Alternanthera species are infected by the Leaf Blight (Phyllosticta amaranthi) which forms small brown spots on the leaves causing them to curl and die.

Aloe, Astrophytum, Copiapoa, Echinocactus, Espostoa, Ferocactus, Gymnocalycium, Kalanchoe and Schlumbergerera species are infected by Bipolaris Stem Rot (Bipolaris cactivora). This infection affects many cacti species causing rot in the stems with a blackish appearance.

Amelanchler is affected by the Witches Broom (Apiosporina collinsii).

Antirrhinum species are infected by the Blight (Phyllosticta antirrhini) that forms light brown spots on the upper-side of the leaf and on the stem. As the spots enlarge they turn greyish with black fruiting bodies in the centre, then become brown and killing the affected areas.

Begonia species are infected by the Stem Rot (Pythium ultimum) turning stems black then becoming soft and causing the plant to collapse. This is the same fungus that causes Damping-off.

Betula species are affected by the Leaf Blister (Taphrina bacteriosperma) which curls the leaves and forms reddish blisters.

Chamaedorea and other cain-like species are infected with Gliocladium Stem Rot (Gliocladium vermoseni) which forms a dark basil stem rot generally on damaged plants and produces orange-pink spores.  The mature leaves are first affected and eventually the stems or cains rot and die.

Crocus and Gladiolus species are infected by the Dry Rot (Stromatinia gladioli), which causes lesions on the corms and rots the leaf sheath.

Crocus, Iris, Tulipa, and Narcissus species are infected Copper Web ((Rhizoctonia crocorum).

Dianthus species are infected by Phialophora Wilt (Phialophora cinerescens) that causes the leaves to fade and plants to wilt. There is obvious vascular discoloration which is very dark. It is not found in Australia.

Erythrina x sykesii may be infected by the Root Rot Fungi (Phymatotrichum omnivorum).

Fern species are infected by Tip Blight (Phyllosticta pteridis). This blight produces ash-grey spots with purple brown margins and the fruiting bodies appear as black pimple like spots.  It is transmitted by air or moisture and in infected fronds become brown and die.  Control methods include sprang fungicide on leaves or reducing humidity and avoid wetting the fronds.

Forsythia species are infected by Stem Gall (Phomopsis species). It forms rounded growths along the stems causing them to die and look unsightly.

Gladiolus species are infected by Penicillium Rot of Corms (Penicillium gladioli). This disease forms deeply sunken reddish brown areas that become corky and produce a greenish fungal growth.

Hedera species are susceptible to several Fungal Leaf Spots including (Glomerella cingulate), (Phyllosticta concentrica) and (Ramularia hedericola). All of which cause yellowish spots that develop into dry brown blotches that kill the leaf.

Larix species are susceptible to Leaf Cast (Hypodermella laricis). This fungus attacks the needles and spur shoots turning them yellow at first then brown after which small black fruiting bodies appear on the leaves during winter.

There are several other fungi including (Cladosporium species) and (Lophodermium laricis) cause leaf blight or leaf casts.

Orchids such as Cattleya, Cymbidium, Cypripedium, Dendrobium, Epidendrum, Oncidium, Paphiopedilum, Phalaenopsis and Zygopetalum species are infected by Phomopsis Rot (Phomopsis species). This fungal problem forms a firm brown rot that appears on the leaves, pseudobulbs and rhizomes. The affected areas have yellow margins and the centre is covered in tiny black specks (fruiting bodies). Cattleya species are particularly susceptible. These plants are also infected by Psudobulb Rot (Mycolleptodiscus coloratus implicated). Dark spots appear on the pseudobulbs eventually causing extensive rot and killing the bulb.

Palms are infected by the fungus Butt Rot (Ganoderma sulcatum). The fungus entered the lower trunk normally as a result of mechanical damage (lawn mower). Symptoms include stunting of new growth and yellowing of the lower leaves. Fruiting bodies become evident at the base of the trunk. There is no effective control method and replanting in infected soil should be avoided.

Kikuyu Yellows     

Pennisetum clandestinum (Kikuyu) is susceptible to Kikuyu Yellows (Verrucalvus flavofaciens), thisis a water mould that infects the roots and causes them to rot. The infection extends up the stem and onto the leaves with yellow discolouration and can be limited to a small or large area up to 1m (3ft) wide.

It is found in warm temperate to sub tropical regions and dispersed in infected soil or plant material. There is no chemical control, nitrogen fertiliser masks the symptoms and complete fertiliser encourages stronger roots to fight the disease.

Pittosporum, Antirrhinum, Aquilegia, Echinops and Orchid species are infected by the Stem Rot or Basal Rot (Pellicularia rolfsii) commonly in the northern hemisphere and preferring humid glasshouse conditions.

Solidago species are infected by the fungal Scab (Elsinoe solidaginis) which covers the leaves and stunts the growth of the plant. Young plants may be killed.

Trillium species are infected by the stem rot (Pellicularia rolfsii) and ( Ciborinia trillii). This normally occurs in wet soils and is detrimental to the plants life.

Tsuga species are infected by Sapwood Rot or Butt Rot (Ganoderma lucidum) and (Coniophora puteana), which attacks the sapwood close to the bark, towards the base of the tree. Commonly killing the host.

Tulipa species are affected Blue Mold (Penicillium species) and the fungus (Rhizopus stolonifer) causing rot in the bulbs.

Vinca species are infected by the soil born Root Rot (Pellicularia filamentosa) which rots the stems and roots.

Viola species may be infected with the Scab (Sphaceloma violae) which attacks all parts of the plant including the seed capsule forming yellowish spots that turn brown and in leaves fall out. Stems and petioles can be girdled killing the upper part.

Viola species are also infected with the Stem Rot (Myrothecium roridum) which attacks the stems at ground level causing them to become dry and brittle. The leaves show symptoms by turning purplish-black and this fungus also infects Alcea and Antirrhinum species.

Non-chemical Control

Generally remove and destroy any infected plants or plant parts, when replanting, avoid using susceptible species for 3 years.  When growing crops space the plants to reduce the humidity and airflow and cultivate the soil to increase the drainage.  Remove weed growth from around the susceptible plants.

Avoid over watering the surrounding soil which encourages fungal development. In the case of trees remove any infected branches and heavily infected trees should be cut down and removed. This infected material should be disposed or burnt. Damaged trees should have the wounds dressed and sealed as a preventative measure particularly for Dieback in Camellia.

Deter Potato Gangrene by planting clean stock and be careful not to damage the crop when weeding. When harvesting the tubers choose a dryer period and be careful not to damage them.

     Fairy Rings

Fairy Rings in Turf are difficult to control and may appear or disappear sporadically. Cultural practice such as minimal thatch build-up, regular aeration and a reduction of organic matter spread on the turf will reduce infection.

Chemical Control

No suitable fungicides available, though drenching or spraying the soil with the fungicide dichloran helps control soil born fungi.

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

DISEASE

   NAME

     Chlorosis in Azaleas

     Iron Deficiency

Description

Lack of available iron in the soil or if the soil is too alkaline for the absorption of iron.

Symptoms

The interveinal areas of young leaves become yellowish to white and the margins may become dried. Affected leaves may be smaller than normal and fall prematurely. Twigs and new branches may suffer from dieback.

Favoured Conditions

It is more prevalent in alkaline soils or soils that have had excessive lime added. Planter beds in and around concrete suffer from leaching.        

Affected Plants

A wide range of plants that prefer acid soils, these include Azaleas, Hydrangeas, Gardenias and Euphorbia pulcherrima, Dillenia indica. All are susceptible to chlorosis.

Non-chemical Control

For infected plants apply iron chelates slowly over several weeks in dilution, on the soil and foliage. As a preventative measure, do not apply lime, superphosphate or ash to the soil and when fertilising select a type suitable for acid loving plants, such as blood and bone.

Chemical Control

Iron sulphate or iron chelates can be applied either to the soil or to the leaves as a foliar spray.

DISEASE

   NAME

     Phytophthora Rot

     Phytophthora species

Pathogen Name

A number of Phytophthora species cause these diseases but the most important species in Australia is the cinnamon fungus, Phytophthora cinnamomi. This species is exotic to Australia and probably originated from south east Asia; it has probably been present in Australia for close to 200 years. Phytophthora are fungal-like organisms that are related to some protozoa and algae; they are microscopic and cannot be observed by the naked eye.

Description

There are many types of Phytophthora Rot but generally the disease affects the plant by causing a soft rot of the affected plant part. The most common form of the disease is a rotting of the roots that occurs below ground with no visible symptoms of the disease above ground until the disease starts to cause leaf drop.

Symptoms

The disease is initiated below ground in the soil, usually on the feeder roots of a plant. The pathogen grows through the roots killing cells and eventually causing an extensive root decay. This causes the infected plant to lose vigour and the leaves to yellow and die. Entire branches starting from the top then die, quickly during hot weather or linger for months. The infection occurs on the root hairs causing small and large roots to rot.  The symptoms of the disease are often very difficult to differentiate from drought symptoms, mainly because the affected root system prevents the uptake of moisture from the soil. Once the disease has progressed far enough large branches will die causing the typical dieback symptoms.

  

                 

There are a number of other diseases caused by Phytophthora species

Twig Die Back (Phytophthora ilicis) attacks Ilex species causing black leaf spots and black stem cankers.

Phytophthora cactorum is known by several common names depending on which plant is being attacked and they have various symptoms. Plant species are listed below.

Root Rot (Phytophthora richardiae) infects Zantedeschia species causing the leaves to turn yellow, wilt and die. Flowers are deformed if they bloom and the infection can also be seen in the new growth, eventually killing the plant. On inspection the roots show signs of decay.

Stem Rot (Phytophthora cryptogea) infects the roots and stems turning them brown and seeds are also attacked causing decay. It is commonly found on Tagetes erecta and infected plants wilt, collapse and die.

Source and Dispersal

Sporangia     Zoospores    

Image by Dr Brett Summerell

Phytophthora species produce sporangia that contain specialised zoospores that have flagella that allow them to move through the soil moisture small distances. These spores encyst on the root and then penetrate the root. The pathogen also produces chlamydospores, specialised survival spores that allow it to survive in the soil for extended periods of time. The chlamydospores can be transported in soil, even extremely small amounts, allowing the pathogen to be dispersed very easily throughout an area and from one location to another. The zoospores are easily moved in water flowing through soil and so are easily dispersed down slopes. It is not uncommon for the disease to move in fronts down a slope.

                  Chlamydospores, specialised survival spores

Image by Dr Brett Summerell

Favoured Conditions

Phytophthora root rot is favoured by poorly drained soils or in soils that are waterlogged for short periods of time. The disease generally occurs during periods when the temperature is above 16ºC although it has been observed in snow gum country in the Barrington Tops National Park and in southern Tasmania. It also prefers soils that have little organic material.

        

Affected Plants

                  Xanthorrhoea species

Image by Dr Brett Summerell

The host range that is attacked by Phytophthora cinnamomi is enormous and is still not well understood but includes many Australian native plants, Rhododendrons, Acer  and Prunus species, conifers, cabbage tree and strawberries. Some Australian plant families that are quite susceptible include species in the Proteaceae, Epacridaceae and Xanthorrhoea species.

Alphitonia excelsa

Alphitonia excelsa can be infected by Phytophthora cinnamomi causing loss of foliage, death of the upper branches and cankers on the trunk.

Cactus such as Cereus species may be infected with Slimy Collar Rot (Phytophthora cactorum) which forms a soft black area at the base of the plant that is water soaked.

Chamaecyparis species may be infected with the Root Rot (Phytophthora lateralis) that attacks roots, trunk, stems and leaves.

Cornus species are infected by Crown Canker (Phytophthora cactorum) and in this case the tree is partially infected initially with one side producing smaller leaves that turn reddish in late summer. The leaves may also shrivel and die prematurely, during dry periods and small and large branches die. After a couple of seasons the tree becomes completely infected with poor top growth and an inconspicuous canker develops at the base of the trunk. Eventually the tree dies.

Erica species are infected by (Phytophthora cinnamomi). The symptoms include foliage turning greyish towards the top, and then the plant wilts then dies with evidence of infection at the base.

Phytophthora in Eucalyptus species
Image by B. Sonsie



Image by Dr Brett Summerell

Eucalyptus species are infected by Phytophthora cinnamomi causing rapid die back of the tree with blackened trunk loss or upper growth and is a serious problem for certain species such as Eucalyptus diversicolor (Karri).

Euphorbia pulcherrima is susceptible to Root Rot (Phytophthora and Pythium species). Roots become dark and the rot can extend up the stem. The plant is also susceptible to leaf blight resulting from the same fungal disease.

Hedera species are infected by Phytophthora Blight (Phytophthora palmivora). This fungus causes leaf spots, foliage blight and stem rot.

Palms such as Archontophoenix, Caryota, Chamaedorea, Cocos, Dypsis, Howea, Liculia, Linospadix, Livistona, Phoenix, Ptychosperma, Rhapis, Roystonea, Syagrus, Washingtonia and Wodyetia species are also susceptible to Phytophthora Blight forming large irregular areas on the fronds that become dark and rotten and limited by the veins

Lilium species are infected by Foot Rot (Phytophthora cactorum) which attacking the stems just below the soil level causing the plant to topple and if infection occurs as the leaves are emerging the base of the infected leaves which collapse remain attached to the bulb.

Morinda citrifolia is infected by Phytophthora Blight, black flag disease (Phytophthora species) which causes the foliage to turn black and limp. The fruit and stems are also infected causing them to turn brown-black and whither.

                  Morinda citrifolia

Orchids such as Cattleya, Cymbidium, Cypripedium, Dendrobium, Epidendrum, Paphiopedilum, Phalaenopsis and Zygopetalum species are infected by Black Rot (Phytophthora or Pythium species). This causes the leaves, pseudobulbs, rhizomes and roots to form a dark soft rot, normally occurring towards the base of the plant.

Saintpaulia, Dianthus, Gypsophila, Limonium and Anemone species are infected by Root and Crown Rot (Phytophthora nicotianae). This is a fast moving fungus that turns the roots blackish then extends to the crown and petioles causing wet rot of the crown then wilting, eventually killing the plant. When found as Phytophthora Leaf Spot or Blight, angular spots appear with water-soaked margins as in Cordyline and Philodendron species.

Sedum species can be infected by up to three Stem Rot fungi including (Colletotrichum species), (Phytophthora species) and (Pellicularia filamentosa). Commonly occurring in wet soils.

Ulmus and Acer species are also infected by (Phytophthora cactorum) and this is known as Bleeding Canker. This casual disease initially causes cankers in the bark that ooze sap and the sapwood forms reddish lesions with greenish margins. The leaves on affected branches turn yellow, wilt then die and mildly affected trees may survive.

Many species are infected by the Bleeding Canker including Acer platanoides, Acer rubrum, Acer pseudoplatanus, Acer saccharinum, Betula species, Liquidambar styraciflua, Aesculus x carnea, Tilia, Salix and Quercus species.

Non-chemical Control

The most effective control for all Phytophthora diseases is prevention primarily because it is extremely difficult to control Phytophthora diseases after they are established in the plant. As Phytophthora species are most easily transported in infested soil quarantine is an essential component of control of the disease and it is for this reason many areas have hygiene protocols to stop the pathogen being introduced into an area.  It is recommended that bush walkers take care not to introduce the pathogen on their boots into un-infested areas and for this reason it is suggested that walking boots be cleaned and preferably sterilised (with 70% methylated spirits) prior to starting a walk.

Cultural techniques such as cultivating the soil regularly with added animal manure and other organic substrates to ensure there is good drainage will also help to minimise the impact of the disease. The plants can be mulched with straw or other organic material taking care that the base of the trunk is left clear. Avoid over watering the soil and observe hygiene in regards to tools, containers or shoes to reduce spreading the infection.

Potting mixes should be pasteurised for 30min at 60ºC to ensure that they are free of the pathogen. It is also very important to grow pots off the ground to prevent the splash of infested mix or water from an infected plant to clean plants.

.

Avoid damaging the bark particularly at ground level and seal any wounds that occur. If cactus or tree species are infected it is possible to cut out the infected area when first seen in order to contain it. Correct tree surgery techniques are required for large trees.

Chemical Control

There are a number of fungicides that are registered for use in the control of these diseases. The most effective chemical control are based on the use of chemicals containing potassium phosphonate. This chemical effectively enhances the defence systems of the plant and has been shown to be most effective in controlling Phytophthora diseases. It is essential that the chemical be applied when the plants is exporting nutrients to the roots, so this is best in the warmer months. The chemical can be applied as a stem injection or a foliar spray, and in some situations as a soil drench.  There are specialised stem injecting equipment available for stem injections on larger trees.

Image by Dr Brett Summerell

Note

Always read the label for registration details and direction of use prior to application of any chemicals.

Amendments by

Dr Brett Summerell
Director Science and Public Programs
Royal Botanic Gardens Trust, Sydney

DISEASE

   NAME

     Sclerotinia Rot, Crown Rot

     Sclerotinia species

Description

A fungal problem that attacks plant parts causing them to collapse and rot, including flower, leaf and stems.

Symptoms

This fungus attacks all the above ground parts of the plant but commonly infects the stem at the base, where it forms a soft, light brown watery rot that spreads rapidly. Under humid conditions the rotted areas forms white fluffy mycelium on which black sclerotia up to 10mm long develop.  These sclerotia also form within the stem in affected areas.  When leaves are infected the tissue may brown and dry out, especially during arid conditions.  The resulting affect of infection is the death of the plant.  

Image by B. Sonsie

Crown Rot (Sclerotium delphinii) causes leaves to turn yellow then become dry, and blossoms to wilt eventually killing the entire plant. It is found on Scilla, Viola and Delphinium species.

Flower Blight (Sclerotinia camelliae) infects flowers either by attacking the top of the petals forming brown specks or at the base of the flower where the petals turn brown then fall with out any sign of rot. The fungus develops on the fallen petals where microconidia are produced under moist conditions and eventually sclerotia appear. This form of the fungus can overwinter either above or below soil level until favourable conditions occur, then the spores are released and dispersed by wind.

Source and Dispersal

Sclerotia are found in the soil or on other infected plants and released spores are dispersed by wind.

Favoured Conditions

Prefers cool moist conditions with temperatures from 10º to 25ºC and is more common from autumn to spring when it is wet.  

        

Affected Plants

A wide range of plants can be infected included French beans, peas, celery, cabbage, cauliflowers, carrot, parsnip, dahlia stocks, primula and many weeds.

Actinotus, Dampiera, Westringa species and Helichrysum bracteatum are infected by the Crown Rot (Sclerotinia rolfsii). Basial rot of the plant with cottony fungal growth and is associated with root congestion. Certain species of orchid may also be attacked.

Allium species are infected by the White rot (Sclerotium cepivorum) which is a major fungal disease of plants.

The bulb rot  and are covered in mycelial which develop small black sclerotia (fruiting bodies) and infected plants may fail to produce flowering stem with the leaves become covered in a white mould, turning yellow then dieing off. It is commonly transmitted by infected seedlings and diseased plants should be burnt.  Avoid re-planting Allium species in the infected soil where the spores overwinter. Soil may be infected for several years.

Antirrhinum, Aquilegia, Lobularia and Mathiola species are attacked by the Stem Rot (Sclerotinia sclerotiorum ) which infects the stigma travelling downwards through the flower into the stem where water soaked areas appear causing it to collapse. The flowers become pale and the entire plant may collapse. On inspection flat sclerotia may be seen in the stem.

Camellia species may be infected by Flower Blight (Sclerotinia camelliae) which causes blooms to fall and Stem Rot (Sclerotinia sclerotiorum).

Hyacinthus species can be infected by the fungus Black Slime (Sclerotinia bulborum) that causes the leaves to turn yellow then fall and bulbs to disintegrate.

Iris species are infected by the fungus Rhizome Rot (Botryotinia convoluta) that infects the rhizomes and forms black sclerotia, and is normally found on dieing plants during spring.

Turf Grass in warm climates is susceptible to Rolf's Disease (Sclerotinia rolfsii). The fungus infects the turf causing isolated dead patches up to 450mm across from spring to summer. As it progresses the dead patches increase in size and the white cotton-like mycelium can be seen in the underlying soil. It is not regarded as a major problem, with minor attacks on Cynodon dactylon (Couch) and Zoysia species.

Non-chemical Control

Initially remove and destroy any infected plants, when replanting, avoid using susceptible crops for 3 years.  Space the plants to reduce the humidity and airflow and cultivate the soil to increase the drainage.  Remove weed growth and leaf or flower litter from around the base of the plants to reduce the development of spores

Turf Grass culture such as aerating soil and maintaining a neutral pH helps prevent infection of Rolf's Disease.

Chemical Control

No suitable fungicides available, though drenching or spraying the soil with the fungicide dichloran helps control it.