Hippeastrum vittatum

PEST

   NAME

     Caterpillars (General)

     Various species

Description of the Pest

There are many types of caterpillars from moths or butterflies, cutworms, bag moths, case moths, leaf rollers leaf skeletonises. The larvae generally eat leaves, seeds, flowers or buds by chewing out pieces. The size of the piece will depend on the size of the caterpillar and generally they are voracious eaters. The method of eating varies such as the leaf skeletoniser which leaves a network of veins or whole leaves are consumed.

The larvae have mainly 4 or 5 pairs of prolegs except Loopers which have 2 -3 pairs of prolegs. The number of prolegs can help in identifying the insect.

Small and Large Types     

Casuarina Moth (Pernattia exposita) is gregarious, brown with a large head and tufts of hairs that line the slender body. It grows to 25 mm long and forms a tightly woven cocoon on the side of branchlets. The large female adult moth has a stocky body and generally slow moving, the male is smaller.

The larvae cause extensive damage to A. littoralis, A. stricta, C. cunninghamiana, C. glauca, and C. equisetifolia.

The hairy larva feed on the 'leaves" phyllodes, and stems, this can lead to ringbarking and death of branches.

Monitoring

Place sheets on the ground and disturb (shake) the tree for the larva drop to the ground on silken threads.

Spruce Budworm (Choristoneura fumiferana) is a reddish brown with a yellow stripe on its side and chews on the opening buds and the needles of the host. The adult moth is dull grey with brown bands and spots on the wings, appearing in early summer.  The larva is very destructive in northern hemisphere coniferous forests.

Banksia Moth (Danima banksiae) is a caterpillar up to 60 mm long and is brown with black and white markings on its sides and when disturbed it arch backwards and reveal an extruded red underside, close to its head. The grey adult moth has an orange coloured body with a wing span that is up to 80mm across with black and white markings.

Banana moth (Opogona sacchari) is in the order Lepidoptera. This nocturnal moth as a wing span up to 25 mm wide and is bright yellowish brown with a dark brown spot on the wings.  It has a life cycle that lasts approximately 3 months with the eggs hatching in 12 days and the whitish larva with a reddish brown head is up to, 26 mm long, and lives for 50 days at 15° C. In warmer climates life cycle is quicker with up to eight generations per season. The female moth uses a ovipositor to lay up to 500 eggs in groups of five amongst the crevices of the plant. The voracious larvae tunnel into the plant, avoiding light.  In bananas it infests developing fruit and in ornamental plants it prefers the fleshy stems, particularly in cacti, begonias, African violets and is also a serious pest of Pritchardia and Chamaedorea species. Symptoms include tunnelling activity, which may be difficult to see then dead areas appear on the stems. As the caterpillars destroyed xylem tubes leaves begin to wilt and the plant may collapse and die. In European countries it is a glasshouse pest that is controlled chemically.

Pritchardi species      Banana moth larvae

European Pine Shoot Moth (Rhyacionia buoliana) lays eggs on Pinus species during late spring on the new buds and the emerging caterpillars in late summer feed on the shoots causing them to fold and become deformed, eventually dieing.  A major problem in the pine forests of the northern hemisphere

Large Grass Yellow Butterfly (Eurema hecabe) is a small attractive yellow butterfly. with a wing span of 40 mm that lays its eggs on the feathery leaves on Acacia species such as A. baileyana, (Cootamundra wattle), A. spectabilis (glory wattle). Other plant foods include Cassia spp, Caesalpinia spp, Senna spp. Albizia julibrissin (silk tree) A. paraserianthes (Albizia) sp Aeschynomene sp (Budda pea), Indigofera australis (Australian indigo's), Sesbania cannabina (yellow pea-bush), Senna surattensis (Glossy shower), Leucaena leucocephala (wild tamarind).

The small lava are up to 15mm long, green with white lateral bands and feed on the leaves at night in small groups, hiding under the leaves during the day. Large infestations may strip trees and require control. The larva of this insect does not feed on grasses. The adults are important pollinators of many Australian native plants. Various sub species of this insect are found through out Asia.

Gypsy Moth (Porthetria dispar) lava is a hairy grey caterpillar that is marked with blue and red dots along its back and can grow to 75mm long. It is capable of defoliating large trees and is a major problem for several species. A major problem in the northern hemisphere.

Lawn Armyworm

Lawn Armyworm (Spodoptera mauritia) is a plump, smooth caterpillar that is darkish brown to black with multiple stripes and pattens along its body. It can grow to 50mm long and tapers from the head. They are gregarious and move around in groups, like an army. If disturbed the larva drop to the ground and curl up, "faking death"  The larva pupate in the soil. They are a pest of grasses and monocotyledon crops mainly.

This insect is also found throughout Asia.

Monitoring

Drench a known area with old fashion soap 2L / 1000 cm 2. Note the numbers of larvae emerging.

Oblique-banded Leaf Roller (Choristoneura roseceana) lava feeds on the leaves and forms a nest by drawing the leaf margins together using silk threads. The adult moth is up to 25mm across the wingspan and is reddish brown with three darker brown bands across the wings. This is a problem in the apple growing areas of North America. It feeds on Maples, hawthorns, crab apples, Blackberry (bramble) and raspberries.

Red Humped Caterpillar (Schizura concinna) is a lava has a red head and humps with yellow and black strips on the body. It grows from eggs that were laid on the underside of leaves by the adult greyish brown moth that has a wing span up to 30mm across.

Tailed Emperor Caterpillar (Polyura pyrrhus spp. sempronius) adult is a large butterfly with a wing span up to 110 mm with four long tapering tails and the rear of the wings. The fleshy caterpillar with four obvious backward facing horns on a shield shape head. It is dark green with yellowish bands and transversal stripes over its back and grows up to 80 mm in length.

It is commonly found solitary or in small groups. Found over much on mainland Australia. The adults are attracted to overripe fruits they become drunk on this and so are easy to capture. The larvae feed on many plants including, Acacia baileyana (Cootamundra Wattle, A. spectabilis (Glory wattle), Delonix regia (Poinciana), Cinnamomum camphora (Camphor laurel) Robinia pseudoacacia (Black or false locust) Lagerstroemia indica (Crepe Myrtle), Argyrodendron actinophyllum (Black booyong), Celtis spp (Hackberry), Brachychiton spp (Kurrajongs) Gleditsia triacanthos (Honey locust).

Verbena Moth (Crambodes talidiformis) lays its eggs on the outside of the plant and the small green caterpillar that attacks seed pods by entering and eating the contents. It half emerges while pupating appearing as a small brown bump circled by a black ring. Native to North America

White Tussock Moth (Hemerocampa leucostigma) produces lava that is up to 50mm long. It has a red head with a yellow body that is marked in black and has four tufts of hair. The caterpillars pupate on the branches and the eggs laid by the adult moth overwinter on the trunk and are covered in a white waxy material. They are found on Aesculus species. A pest in North America of Oaks.

Life Cycle

This insect has a Holometabolous life cycle, i.e. it has a larval and a pupal stage.

Distribution of the Pest

Many species are found throughout the world from tropical to temperate regions and most of the adults are capable of by flying

Many hairy caterpillars can be irritating      Leaf Skeletonised

Period of Activity

Most active during the warmer months from spring to autumn.

.

Damage Caused

Leaf Rollers

Caterpillar Inside a Tomato

Susceptible Plants

A wide range of native and exotic plants are attacked and can be a major problem in commercial crops or turf grasses. Plants with soft-textured foliage (eg vegetables, some indoor plants) are preferred, but trees and shrubs are commonly attacked.

Malvaceae Abutilon spp, Hibiscus spp and other members of the family are attacked by the castor oil looper, Croton caterpillar (Achaea janata) which feed on leaves. The tip borer Cotton tipworm (Crocidosema plebejana), Rough bollworm (Earias huegeliana) which feeds on young stems, flowers and seeds. A leaf miner (Phyllonorycter spp)

Acer saccharinum and Fagus species are attacked in North America by the Maple Leafcutter (Paraclemensia acerifoliella) that forms a small cocoon in leaves that it skeletonises.

In Australia Case moths and Painted apple moths (Teia anartoides)

Ailanthus altissima is attacked by the Cynthia Moth (Samia cynthia) light green lava, which eats leaves and the Ailanthus Webworm (Atteva aurea) which are olive-brown caterpillars that form web nests in the leaves.

Antirrhinum species are attacked by the Leaf Tier (Udea rubigalis) lava. This caterpillar eats pieces out of leaves and binds them together forming a nest. It is more commonly found in glasshouse culture.

Berberis species may become infested with the Barberry Worm (Omphalocera dentosa). This small caterpillar is black with white spots, up to 14mm long and feeds on young shoots and leaves. It also binds the shoots with a silken thread to form a nest.

Betula species are attacked by the Leaf Skeletonizer (Bucculatrix canadensiella). The small adult moth has brown wings with a whitish underside and its yellow green, 7mm long lava skeletonise the undersides of the leaf turning it brown.

Brachychiton, Senna and feathery-leaved Acacia species are attacked by the Tailed Emperor Caterpillar, particularly in dryer periods.

Catalpa species are attacked Catalpa Sphinx (Ceratomia catalpae). This large yellow and black Caterpillar grows to 76mm long and attacks the leaves.  Large infestations can completely stripped a tree and control is carried out by spraying.

Calendula and Canna species are attacked by the Woollybear Caterpillar (Diacrisia virginica) which has yellow and black lines down its body is up to 50mm long and eats the leaves or flower buds. In Canna species the chewed holes tend to be in a straight line across the leaf.

Celtis species are attacked by the Spiny Caterpillar (Nymphalis antiopa) which is reddish, up to 50mm long and feeds on the leaves at the top of branched in groups.

Cheiranthus species are attacked by the Diamond-backed Moth (Plutella maculipennis) lava, which is a small green caterpillar to 14mm long that feeds on the underside of leaves and may form a shot hole appearance. It forms a small cocoon to pupate in and in cooler climates it may be found in glasshouses.

Cotinus, Fraxinus, Betula, Cornus, Crataegus, Aesculus, Tilia, Acer, Quercus and Populus species are susceptible to attacked by the Oblique-banded Leaf Roller (Archips rosaceana)

Iris and Antirrhinum species are attacked by Verbena Moth.

Picea, Abies, Tsuga and Pinus species are attacked by Budworm commonly found in the northern hemisphere.

Populus and Carya species are attacked by the Red Humped Caterpillar which chews the leaves.

Quercus species are attacked by several caterpillars including Saddleback Caterpillar (Sibine stimulea) and Datana Caterpillar (Datana ministra) that feed on the leaves.

Samanea saman is attacked by several caterpillars (Ascalapha odorata, Polydesma indomita and Melipotis indomita). These caterpillars defoliate the tree but cause no long term problems.

Spiraea, Fraxinus, Betula, Cornus, Crateagus, Acer, Quercus and Populus species are attacked by the Oblique-banded Leaf Roller.

Ulmus, Salix, Crateagus, Tilia, Quercus and Populus species, Pseudotsuga menziesii are attacked by the Gypsy Moth (Porthetria dispar).

Ulmus species are attacked by the Spring Cankerworm (Paleacrita vernata), which chews the leaves during spring and the Fall Cankerworm (Alosphila pometaria), which also eats the leaves during autumn. Ulmus  species are also attacked by several caterpillars including the lava of the Leopard Moth (Zeuzera pyrina) and the Tussock Moth (Hemerocampa leucostigma).

Cultural Control

Small numbers may be removed by hand and squashed while others species such as the Casuarina Caterpillar drop to the ground when disturbed by hitting with a stick or shaking the plant. On the ground they can be squashed or collected and placed in a bucket of soapy water.  All rubbish around plants and glasshouses should be cleared as certain moths overwinter in such places.

Biological Control

There are many natural predators that reduce numbers including birds, lizards, frogs; other predators are wasps, viruses, and fungi.

Chemical Control

The small plant may be sprayed using Pyrethrum-based insecticide to reduce numbers or dusted with an equally environmental friendly chemical. In severe cases crops may be sprayed with Carbaryl.

Note

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

PEST

   NAME

     Slugs and Snails

     Various Snails Species

Description of the Pest

Slugs and snails are land molluscs. Snails produce an external spiral shell; slugs do not. The common garden snail Helix asperasa, grows up to 25 mm, long. Its body is slimy, broad, elongated and greyish, with two pairs of reticulated tentacles, with eyes at the ends of the longer pair. The mouth parts of snails and slugs contain a file-like organ known as the radula, which is used to rasp away at the host plant's tissue. Movement of the animal is by a muscular sliding movement, along a slippery trail of mucous; this solidifies on exposure to the air (typically described as a "silvery trail").

                 

Appearance and Distribution of the Pest

Slugs and snails occur world-wide. Slugs tend to be more prevalent in heavier soil types.

Life Cycle

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

Snail eggs are laid in moist soil, 20-40mm deep; eggs are white, spherical and appear in clusters of 30-100. Under favourable conditions, eggs hatch in 2-3 weeks. Newly emerged snails resemble tiny adults. When the weather is cold and dry, snails seal themselves into their shells where they survive, dormant, for 1-3 years.

Period of Activity

More active during the warmer months, although some species may remain active throughout the year.

Damage Caused

Native Australian slugs and snails are not commercial pests. Introduced species chew holes in foliage or skeletonise leaves; some plants may be completely defoliated plants; tubers and seedlings may be completely eaten. Slugs and snails feed mainly at night, especially after rain or watering; they shelter in cool, moist locations during the day. When the weather is dry, snails seal themselves into their shells with a mucous membrane, where they survive, dormant, for 1-3 years. Some species may consume up to one third of their body weight each day.

                 

Susceptible Plants

A wide range of leafy plants, including ground crops, potatoes, tubers, leafy vegetables and seedlings.

Fern species are attacked causing serious damage. New fronds are repetitively eaten causing the plant to become stunted. Attacks are normally more severe during wet periods during which time control measures should be taken.

Morinda citrifolia is attacked by the Giant African Snail (Achatina fulica) which defoliates trees.

                 

Cultural Control

Remove possible hiding places and avoid overhead watering to reduce humidity. Cultivate soil regularly; in commercial situations, allow the soil to remain fallow for one season to reduce numbers. Domestic infestations may be removed by hand. Traps may be created by inverting small pots near where snails and slugs are feeding; they will gather in these shelters during the day, and may be collected and destroyed. The popular Australian "beer trap" consists of a vertically-sided container, sunk into the ground and filled with beer, which intoxicates and drowns the snails.

Biological Control

Natural predators such as birds, frogs, and lizards reduce numbers, but do not provide effective control. Orchardists have used running ducks to control snails with some success.

Chemical Control

Commercial baits - molluscicides - made from methiocarb or metaldehyde are effective when used in combination with sanitation. Their effectiveness varies according to soil and weather conditions; it is generally recommended to avoid watering after application.

Note

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

PEST

   NAME

     Cutworms

     Agrotis species

   ORDER

     Lepidoptera

   FAMILY

     Noctuidae

Description of the Pest

Cut worm larvae live in the soil, congregating in weedy areas; they chew off young seedlings at the base. They are smooth, thick fleshy grubs that vary in colour, from pinkish brown to olive green, or almost black. They grow up to 40mm long and 5mm thick. Larvae curl up when disturbed, pretending to be dead. Larvae burrow down into the soil to a depth of about 50mm to pupate. Adults are dark brown, hairy moths, with a wingspan of about 60mm.

These insects have a Holometabolous life cycle, ie. When metamorphosis is observed during the pupal stage.

    

Appearance of the Pest

Adult moths are strong fliers capable of flying many kilometres laying eggs over a wide area. The eggs may remain dormant for several weeks until it rains or emerge within a few days under the right weather conditions.

Three similar species are commonly found in Australia:

·        Agrotis ifusa (Bogong moth) is up to 50mm across and has three spots on its forewing.

·        Agrotis munda (pink cut worm); and

·        Agrotis ipsilon (black cut worm).

Agrotis munda

Period of Activity

Different species are active throughout the year, their prevalence being determined by rainfall and temperature. They are normally most active at night. Larvae will appear in greatest numbers when favourable environmental conditions produce lush growth.

Susceptible Plants

Cutworms prefer soft, succulent seedlings or fleshy annuals, perennials and a variety for ferns or orchids. They feed at night and remain in the soil during the day.  They are most commonly found in soil that is infested with weeds or soil that is poorly drained and moist. Well-drained soils harbour less lava.

Senecio and Dianthus species are attacked by the Cutworm (Peridroma margaritosa) which eats seedlings, leaves and flower buds. Under glasshouse conditions all stages of the lifecycle are present.

Turf Grasses are attacked by several Agrotis species causing damage during different seasons according to there individual life cycle. All feed at night on the leaves when young and mature larvae shear plants stems at ground level.

Damage Caused

Young larvae feed on the lower epidermis of leaves. Adults attack stems and seedlings at the base, eating the soft new growth, on one side, or completely through. The damaged plant normally topples over (hence the common name). Mature plants may wilt or the foliage becomes yellowish as a result of the damage, but normally recovers.

Cultural Control

Weed removal and cultivation to improve the drainage of the soil will provide some reduction in of numbers. Seedlings may be protected by a physical barrier, (eg plastic tube pushed into the soil around the seedling).  Heavily infected soil can be laid fallow with for several weeks to disrupt the life cycle or the soil can be covered in black or clear plastic until weeds and lava are dead.

A molasses based bait that has hardwood sawdust and bran mixed with water creates a stick mass that the lava is attracted to but cannot escape. At sunrise they die from dehydration.

Biological Control

Natural predators such as birds, ground beetles and certain bugs help keep numbers down. Wasps and certain species of flies also attack the lava.

Encouraging earthworms by mulching and increasing the humus level is an excellent way to rid the soil of lava.

Chemical Control

Chemical treatment (Carbaryl) may be effective if sprayed in the evening, when the caterpillars emerge to feed.

Note

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

DISEASE

   NAME

     Leaf Scorch

     Stagonospora curtisii

Description

This is a casual fungal problem that infects the leaves.

Symptoms

The leaf tips are reddish brown soon after emerging, with small raised or lacerated spots that form longitudinal lines. These spots may also appear on the bulb scales and the flower, turning yellow-brown with a scorched appearance.

The infected areas become thin and papery while the lower leaf forms oval brown spots.  As the spots enlarge the enclosed tissue turns white and dies.  The leaf generally has a pale green washed out appearance and a heavy infection causes the leaf to bend and die.

Slimy base          Clivia miniata

Source and Dispersal

The fungus is found in the bud scales which are normally at ground level. The young leaves are infected as they grow past the scales.  The spores are dispersed by wind or by the introduction of infested bulbs.  

Hemerocallis species      White mycelium

Favoured Conditions

It prefers warm wet conditions that normally occur during spring as the leaves emerge.  

        

Affected Plants

This fungus affects many bulbous plants including Daffodils, Jonquils, Belladonna lilies, Crinums, African lilies, Hippeastrums, Kaffir lilies.

Hemerocallis and Clivia species may be infected Leaf Scorch causing the tips of the leaves to brown off and die.

                  Clivia miniata

Non-chemical Control

Infected leaves should be cut off and disposed of by burning.  Heavily infested bulbs should be dispensed with.

Chemical Control

Preventative spraying of copper oxychloride (fungicide) should be carried out as the leaves emerge.

DISEASE

   NAME

     Virus (Generally)

     Various Virus Species

Viruses can infect any plant and there are hundreds of types, but unlike fungi and bacteria viruses can only reproduce inside a living cell. Viruses are small requiring a magnification of x 10,000 to be seen and infection can be transmitted from one plant to another causing a variety of symptoms. Infected cells normal function, in the plant is diverted to aid the virus to reproduce by supplying nutrients and energy.  The virus can spread from cell to cell or travel through the vascular system in the plant and may only infect a specific part of the plant, normally the new growth or the whole plant.

Lethal Yellowing

This fatal disease is not a virus, but of uncertain origin that is associated with mycroplasmas or mycroplasma-like-organism and infects palms, particularly Cocos nucifera (Coconut Palm).

The symptoms include premature dropping of the fruit at all stages (shelling) and these have brown-black water soaked areas under the calyx.  The second symptom is the blacking of the new inflorescence as it is exposed from the spathe. Male flowers are also blackish and fruit will not set.

The third stage of this infection causes the lower fronds to turn yellow, eventually engulfing the entire crown. The fronds turn brown and easily fall from the plant and the infection kills the entire plant within 3 to 6 months with the crown falling away leaving a bare trunk.

Some palm species only exhibit the third stage making it difficult to diagnose, but generally a solitary frond will turn yellow, known as 'Flagging' and indicates Lethal Yellowing.

It is known to be transmitted by a plant-hopper (Myndus crudus) and currently there is no practical control.

Mosaic Virus generally is a viral problem that involves several viruses altering the production of chlorophyll in the leaf. It may only be seen on certain parts but the whole plant will be infected.

Symptoms

Mosaic Virus on Roses form variable yellow pattens on some of the leaves that are fine lined, imitating the veins with blotches or larger marks forming streaks.

Mosaic Virus on Cabbage, cauliflower and broccoli form yellow rings on immature leaves that turn shades of green as the leaf matures and eventually turning purplish-black in cooler weather.

The virus (Marmor iridis) infects Iris and Watsonia species leaves develop pale green streaks on the leaf that become larger then turn brown eventually killing the leaf. The virus prevails in the rhizome from season to season and is a serious problem reducing and damaging flower production.

Phloem Necrosis (Morsus ulmi) is a serious disease of Ulmus species. The initial symptoms occur at the apex and on branch tips where the leaves droop as the petiole is affected. The leaf margins curve upwards and the leaf turns greyish then yellow and then falls, overall giving the tree a sparse appearance. As the virus matures it infects the phloem tubes turning them yellowish, and then brown eventually killing the cells. The roots die and the entire tree may gradually decline over eighteen months, or in acute cases a tree may die within three weeks.

Pumpkin and zucchini are attacked from a virus commonly known as 'Watermelon virus' which affects the leaves by making them mottled in light or dark green and may become distorted. This inhibits the size of the plant and the fruit may have sunken areas with concentric rings.

Tobacco is infected by a Tobacco Mosaic virus (Marmor tabaci) and a Ring virus (Annulus tabaci).

Tulip Breaking (Marmor mite) causes yellowish-white, light coloured striping or spotting of the flower and reduces the size and vigour of the plant in Tulipa species. It may also affect the growth of the bulb and offsets and is more prevalent in double-flowering varieties.

Yellows (Chlorogenus callistephi) is a viral disease that causes leaves to turn yellow and produces shoots that are simular to Witches Broom or flowers that have poor colouring. The infection will not kill the plant as it overwinters and spreads infection from the living host via the Leaf Hopper (Macrosteles fascifrons). It is not found in the soil or in seeds but is a major problem for Aster species.

Source and Dispersal

The source and the dispersal vary depending on the particular Virus that is involved. In roses the virus overwinters on fallen leaves or pruned pieces of plant material. It is also found on infected plants and is spread by infected propagation material. Aphids transmit this Mosaic Virus.

Infected cabbage, cauliflower and broccoli are an excellent source for aphids, such as the green peach aphid to disperse.

Iris rhizomes are the source and the virus (Marmor iridis) is spread by aphids and infected rhizomes during propagation.

Phloem Necrosis is thought to be transmitted by the Elm Leafhopper (Scaphoideus luteolus) or by infected rootstocks.

Pumpkin and zucchini are infected from surrounding weeds or other infected plants by several aphids including the cotton aphid and the green peach aphid.

Generally plants are infected by viruses by, rubbing against each other or through grafting, budding and other vegetative means such as wounds. Insects also transmit viruses by sucking sap or transferring infected pollen.

Favoured Conditions

Viruses prefer warm humid climate.

        

Affected Plants

A wide range of plants are affected from a range of Mosaic viruses causing simular symptoms. These include roses, cabbage, cauliflower, broccoli, iris, pumpkin, zucchini, turnips, capsicum, swedes, stocks, alyssum and wallflowers. Shrubs and trees such as Ulmus species are also infected.

Abutilon species may be infected by the Mosaic Virus ((Marmor abutilon) which causes variegation of the leaves.

Aquilegi, Berberis Passiflora and Tulipa species are infected by the Cucumber Mosaic Virus (Marmor cucumeris). This causes yellow streaking or mottling in the leaves and dark coloured patches to appear on the flowers. It also stunts the plant and prevents flowering.

Lilium and Tulipa species are infected by the Mosaic virus (Marmor mite) causing yellow mottling on the leaves.

Palms are infected by Lethal Yellowing include, Pritchardia martii and Phoenix canariensis.

Non-chemical Control

With roses if the problem is minor it may be ignored as the flower production will be normal. Heavily affected plants should be disposed of.

Other plants that are infected should be removed and destroyed. The spread may be arrested by the eradication of aphids by applying soapy water.

Chemical Control

Once the virus is seen it is too late to spray. Preventative spraying to control aphids should be carried out in spring using Dimethoate. There is no satisfactory chemical control for viruses.

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

     Armillaria Root Rot, Honey Fungi

     Armillaria luteobubalina

  

Description

This naturally occurring fungus grows between the bark and wood of trees producing distinctive cream sheets of hyphae. The toadstool-like fruiting bodies are yellowish brown and appear from the soil or sprout out of the base of the host plant.

Image by Dr Brett Summerell

Symptoms

This is a vigorous fungus that attacks the roots of trees and is not normally noticed until dieback starts to occur. Affected plants generally appear declined, with some dieback and by this stage; the disease may be well established. Leaves can turn yellow, shrivel and fall from the plant and the branches die back. Citrus trees may produce a heavy crop of fruit just before death. Splits often occur on the trunk of affected trees and the bark may lift revealing white sheets of mycelium or hyphae under the bark. These hyphae will have a distinctive "mushroom" smell. Affected roots become spongy, powdery or jelly-like and when dissected reveal similar white sheaths under the bark. Infected plants may survive for many years before final death of the tree.

                 

Image by Dr Brett Summerell

Source and Dispersal

This fungus is a native species that is naturally found in Eucalyptus forests and woodlands throughout eastern Australia and south-western Australia. It is commonly found on old tree trunks and decaying wood where honey coloured toadstools appear from the base of the host or surrounding soil in May-June. The toadstools produce white spores that are dispersed by wind, but generally the fungus spreads underground through contact between infected and uninfected roots. The fungus can grow about 1-1.5 metres per year along a root. This species, unlike those in the northern hemisphere does not produce rhizomorphs, thick strands that are flat resembling shoe-strings.

Mycelium on wood     

Image by Dr Brett Summerell

The fungus is not spread by contaminated soil as it only grows in root material. Spread to new sites is either through spore movement (very rare), movement of infected plants or through movement of contaminated wood chip used for mulch. Dead or dying trees should be inspected for the presence of this pathogen prior to use as mulch.

This fungus can survive for many years in infested root and stem material depending on the size of the material and speed of decomposition of the wood.

Favoured Conditions

This fungus prefers sandy soil types and is more frequently found in more freely drained soils. Moisture is required for growth of the fungus along the root system. Generally the damage caused to plants is greater on plants that are already under stress or weakened. The retention of infested root systems and stumps in the soil has contributed to an increase in the occurrence of this disease.

Affected Plants

The host range for this fungus is extremely wide and includes many ornamentals and Australian native plants. Fruit trees and perennials are also commonly attacked. The most susceptible species include oaks, camellias, azaleas, roses and eucalypts.

Amaryllis, Narcissus and Hippeastrum species are also infected.

Cedrus species trunk     

Image by Dr Brett Summerell

Cedrus species are also affected by Armillaria root rot causing the roots to rot and the trunk to swell and spilt open. There is no control for these infections.

Non-chemical Control

Control of this disease is totally dependent on removal of the inoculum of the fungus from the soil. To be effective this will require removal of the infested roots and stem, a process that may be difficult in garden beds. Infected plants should be removed and disposed of, but it is not necessary to remove the surrounding soil as the fungus only occurs in the plant.  When clearing affected land for cultivation, remove all stumps and roots and allow 2 to 3 years prior to replanting.

Trees that are in the early stages of attack may be saved by removal of the affected roots and leaving remaining roots exposed for several years. Top soil around the trunk should also be removed for a distance of up to 1m and affected trees should be fertilised and watered to encourage vigour.

Chemical Control

There is no practical or effective chemical control. Fumigation has been carried out to eradicate the fungus but success is dependent on the removal of large sources of inoculum. However many of the chemicals used for this purpose are highly toxic and have restricted usage now.

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