Picture Disease/Disorder
[Alternaria] [Anthracnose] [Bacterial canker] [Black Spot]  [Black Spot on pawpaw] [Black Spot on roses] [Blossom End Rot] [Catface deformity] [Cercospora spot] [Crown Gall]   [Damping Off] [Dieback] [Downy Mildew] [Fasciation] [Fleck] [Fruit splitting] [Grey Mould] [Gummosis] [Herbicide damage] [Leaf curl on peaches] [Leaf spot]  [Leaf spot on hippeastrum] [Melanose on citrus [Nematodes] [Phosphorous induced iron deficiency] [Phyllody] [Pinks disease] [Powdery Mildew] [Rust] [Rust on frangipani] [Rust on lawns] [Rust on myrtaceae-Myrtle Rust] [Scab] [Scab on citrus] [Scab on passionfruit] [Scab on potatoes] [Sooty Mould]  [Stylar End Rot]  [Target Spot] [Woodiness virus on passionfruit] [Wilt] [Vivipary]

AlternariaAlternaria
This fungal disease is a common, but rarely diagnosed disease of back yard fruit. Symptoms may include large leaf spots (pictured); increased leaf drop; tip dieback; brown spots edged in yellow on fruit skin and/or internal fruit rot.

This disease occurs rapidly during mild temperatures with high humidity and/or during rainy or misting conditions. Avoid wetting foliage when watering. Prune dead and damaged foliage and increase air circulation and exposure to direct sunshine. Avoid fertilizing during periods that favour the disease as new growth is particularly susceptible.

Apply casuarina tea [see Do It Yourself Pest Control]; commercial liquid silica and potash or copper-based sprays. Lemons, mandarins, tangelo, oranges and related citrus are commonly affected. Brown spots on fruit of passionfruit are symptom of Alternaria passiflorae. Parsley is affected by Alternaria petroselini.

Mango AnthracnoseAnthracnose
Anthracnose (Colletotrichum species) is a fungal disease exacerbated by rain and high humidity. During dry weather the disease is virtually absent. This disease is the primary reason why mango, avocado, banana, custard apple, lychee, macadamia, passionfruit, carambola and fruit fail to develop or develop fruit that blacken and drop prematurely. Skin of citrus fruit may be affected although flesh generally remains edible.

Apply casuarina tea [see Homemade pest control]; commercial liquid silica and potash; copper-based sprays immediately prior to flowering and during early fruit set to reduce the effects of anthracnose. However, these preparations rarely control the disease if rain and high humidity persist to favour disease development. Where possible, investigate fruit tree varieties with some degree of natural resistance to anthracnose.

Bacterial canker (image by Yvan)Bacterial canker (Pseudomonas species)
Sunken dead patches on stems; shot-hole on leaves; stem dieback and/or oozing of sap from the trunk and branches are common symptoms of bacterial canker. The disease is particularly prevalent on stone fruit. Make clean cuts when pruning to avoid tree damage. Clean pruning tools with disinfectant between cuts or at least between individual trees. Avoid pruning in winter when trees are more vulnerable due to slow callus growth and environmental conditions that support disease growth. Remove badly affected trees. Use commercial tree wound dressings or biodynamic tree paste [see Homemade pest control] or apply a copper-based spray during winter.

Black Spot
Black spot describes the symptoms of a range of bacterial and fungal diseases affecting ornamental and productive plants.

Black Spot on PawpawBlack Spot on Pawpaw
Fungal infections of Asperisporium caricae cause this disease. Natural plant genetics and nutrition are important factors in disease control. Grow plants from seed of pawpaw local to your region. Increase potassium (sulphate of potash and/or lucerne mulch), phosphorous (rock phosphate or chicken manure) and magnesium levels (Epsom salts) to make plants more disease resistant. Incidence of the disease increases during the cooler months when nutrient uptake slows. Apply liquid seaweed to increase nutrient availability and improve cold tolerance.

Apply casuarina spray; bicarbonate of soda sprays [see Homemade pest control]; commercial liquid silica and potash; wettable sulphur or copper-based sprays prior to the onset of and during the cool weather. Wash ripe fruit in water as hot as your hands can stand and dry thoroughly to control fungal and bacterial spores that cause post-harvest fruit rot.

Black Spot on RosesBlack Spot on Roses
The causal agent is the fungus Diplocarpon rosae. Full sun and good air circulation are essential in combating this disease. Avoid wetting the foliage. Water early in the day. Provide balanced nutrition. Apply foliage applications of seaweed and/or commercial liquid silica and potash to increase disease resistance. Fish-based fertilisers also contain trace elements valuable in building disease resistance. Remove infected leaves and collect fallen leaves from beneath plants. Prune out old canes and diseased wood. Dispose of diseased material offsite. Apply bicarbonate soda sprays [see Homemade pest control-Bicarbonate of Soda Spray]; wettable sulphur or commercial potassium bicarbonate products (Eco-Rose). Contact your local rose society for recommendations of disease resistant rose cultivars.

Black spot on citrus is caused by the fungus Guignardia citricarpa and results in freckle and blotches on fruit. Bacterial black spot on mango is caused by Xanthomonas campestris mangiferaeindicae. For management of these diseases follow guidelines as for pawpaw and roses.

Blossom End RotBlossom End Rot
This disorder has two contributing causes - calcium deficiency and irregular watering. When planting tomatoes, capsicum, chilli, tamarillo and related solanaceae plants add calcium in the form of gypsum (powdered or liquid form) or if the pH of the soil is acidic, apply Dolomite lime. Ensure regular watering. Affected fruit cannot be saved and should be removed. If plants are affected early in the growing season, it is possible to apply calcium and improve watering practices to achieved improve the fruit harvest later in the season.

Catfacing deformity on tomatoesCatfacing deformity on tomatoes
Catfacing deformity on tomatoes is a natural characteristic of some heirloom varieties - part of their character. In other instances, fluctuating temperatures are to blame, particularly very warm days (30 degrees) followed by cooler nights (10-12 degrees). Fruit that form on the same plant outside the temperature fluctuations are generally unaffected. Mite and thrip infestations at flowering and first fruit set also contribute to catfacing. Nutritional imbalance, particularly overfeeding with nitrogen increases the incidence of the disease, often affecting the entire crop. Affected tomatoes can be left to ripen and are perfecting safe to eat. Alternatively, you can use them to make sauce, chutney and pickle.

Cercospora On Silverbeet (image by George)Cercospora spot/ Pseudocercospora spot
Environmental conditions play a major role is these fungal disease outbreaks. Cercospora spot is particularly virulent on leafy greens including spinach, silverbeet, lettuce, beetroot and rocket and also attacks succulent plants like yucca. To avoid disease outbreaks by ensure plants have full sun and great air circulation; apply liquid seaweed; avoid watering late in the day; avoid excess nitrogen (overly rich manure, fertilizers) and balance nitrogen with extra commercial liquid silica and potash and trace elements from rock dust or commercial products. Preventative bicarbonate of soda or milk sprays [see Homemade pest control] or commercial sprays based on potassium bicarbonate like Eco-fungicide help minimise disease outbreaks on soft leaf plants.

Corky blisters on fruit surface of avocado is caused by Pseudocercospora purpurea; Black spots on the leaves of coffee plants results from Cercospora coffeicola. Pseudocercospora annonicola attacks foliage and fruit of custard apples. Pseudocercospora macadamiae affects foliage and fruit of macadamias. Bacterial black spot on yucca is caused by Cercospora yucca. Follow general recommendations above.

Crown Gall image (image by Helen)Crown Gall
This bacterial disease (Agrobacterium tumefaciens) potentially affects a wide range of ornamental and fruiting trees, shrubs and vines. Bacteria are persistent in the soil and enter plants via a wound. Galls develop on the below ground stems and roots. These increase in size over time, affecting the growth and vigour of plants. They can eventually reach an enormous size, but often go un-noticed until the plant is removed. There is no treatment for existing infected plants. Avoid planting back into gardens where crown gall has previously occurred.

Prior to planting susceptible species like roses, soak new plants in beneficial mycorrhizal fungi specifically designed to provide protection from crown gall. Proprietary brands include NOGALL which was developed in Australia, but home gardeners may find it very difficult to source this product. Contact your local rose society. Please note mycorrhizal fungi have no curative effect on plants that are already infected.

Damping Off fungusDamping Off fungusDamping off fungus
This disease is caused by one or more fungal pathogens. It affects germinating seeds and young seedlings. It is transferred via water and affects the water conducting tissues of the plant. Use new seed raising mix or sieved compost made using a hot/aerobic method. Wash all pots and tools in hot, soapy water then allow to dry in the sun before use or soak in household disinfectant for 20 minutes. Make sure mix and pots are well drained. Never sit pots in water. There is no cure for affected plants and they should be disposed.

Newly planted seedlings may appear to suffer from damping off when the real cause may be over watering; or planting into soil where excessive fertiliser or rich compost/manure have been applied; or pests such as cutworm and wireworm are present [See picture the pest].

Dieback on frangipaniDieback on pawpaw by ElaineDieback
Black tip fungus and stem dieback on pawpaw and frangipani result in failure to flower/fruit and withered branches. Tip dieback on pawpaw is most common during the summer months. Stem dieback occurs in summer, but is particularly obvious on frangipani during winter when the majority of species are deciduous. Fruit piercing/sucking moths and fruit spotting bugs have been implicated in these diseases. They create entry wounds and transfer disease organisms to the stems and branches of plants.

Minimise outbreaks by planting in full sun and ensuring soil is well drained. Provide balanced nutrition, particularly in terms of calcium (gypsum); silica and potash and trace elements. Prune damaged stems back to healthy tissue and dispose of prunings off-site. Where possible control moth populations over the summer months.

Downy Mildew (image by Lyndal)Downy mildew
This fungal disease affects a wide range of vegetables (particularly cucurbits) and fruit (grapes). Cool, wet or humid conditions favour disease development as does nutrient imbalance (excess nitrogen), lack of sunshine and air circulation and varietal susceptibility. Zucchini, pumpkins and cucumbers are particularly susceptible on cooler conditions. Grapes affected early during the season require treatment, but less so late in the season prior to leaf drop. Downy mildew on roses is caused by Peronospora sparsa. Angular blotches on rose foliage are symptomatic.


Apply bicarbonate of soda spray [see Homemade pest control] or use commercial organic fungicides based on potassium bicarbonate Eco-Carb or Eco-Fungicide. If the underlying causes of the condition cannot be changed, control will be limited. This disease is commonly confused with powdery mildew, but is more difficult to control.

FasciationFasciationFasciation
This describes an abnormality that results in flattening of the stem and shortening of internodes or similar deformities on flowers and seed pods. It occurs randomly and is generally regarded as a curiosity. Prune off the affected stem. It is unlikely that the plant will continue to produce fascinated stems following pruning. However in some cases, fasciation dominates a plant’s growth and commercial growers capitalize this weird growth habit by propagating plants by cuttings or tissue culture to maintain the fascinated appearance. Examples include plants with crested flowers or stems.

Fleck On QuinceFleck
This fungal disease is caused by Fabraea maculata. It attacks pome or pip fruit like apples, pears and quince trees. This disease causes serious defoliation; tip dieback; tree weakening; negatively affects flowering and fruiting and disfigures and marks fruit. Some varieties are more resistance. Ask staff at your local nursery for varieties best suited to your region. This disease becomes most apparent over summer, but preventative action must be taken during winter and/or at first bud burst. Apply seaweed products; increase silica and potassium levels to aid disease resistance and/or apply copper-based sprays.

Split CitrusSplit BananasFruit splitting
Fruit splitting is common to a wide range of ripe and unripe fruit and results from irregular watering. To overcome this problem, water deeply during periods of low rainfall. Be sure to irrigate beneath and beyond the full canopy of trees and along the full extent of foliage on wine crops. Mulch trees and vines well to help maintain soil moisture level. Apply a wetting agent and/or liquid seaweed where soil has become water repellent. Incorporate plenty of organic matter into the soil prior to planting to help the soil hold moisture.

Grey Mould On RosesGrey mould
Cool temperatures, long periods of rainfall or high humidity favour development of the fungal pathogen Botrytis cinerea. Affected flower buds initially display pink spotting on petals and blooms may fail to open. The distinctive grey mould becomes obvious as the disease progresses. Most flowers are potentially vulnerable. Prune off and dispose of disease affected plant material offsite. Avoid overhead watering. Improve air circulation, sunlight and warmth. Apply seaweed products; increase silica and potassium levels to aid disease resistance and/or apply wettable sulphur or copper-based sprays.

GummosisGummosis
Gummosis is a bacterial canker disease that appears as an oozing gummy residue on trees. Injury caused by pruning, insects or environmental stress can cause trees to become infected, particularly stone fruit. Clean the infected area as much as possible and seal wounds with a biodynamic tree paste, commercial tree paste or spray with Bordeaux (lime and copper sulphate). Make clean cuts when pruning to avoid tree damage. Clean pruning tools with disinfectant between cuts or at least between individual trees. Phytophthora root rot caused by poor drainage or over watering can present similar symptoms to gummosis.

Herbicde Damage On Frangipani (image by Anne-Mary)Herbicde Damage On RosesHerbicide damage
Spray drift, accumulation of herbicides in the soil and movement of herbicides through soil in water causes stunted growth and distorted shoots. Glyphosate; Once A Year Path Weeder; Weed and Feed products that attach to a garden hose and selective herbicides designed to kill broad leaf weeds and clover in lawns most likely to be responsible for the damage. All plants are potentially affected. Once contact is made with plant tissue, it cannot be removed. The plants will never grow out of the damage even if pruned and fertilized. Remove damaged plants.

Leaf Curl On PeachesLeaf curl on peaches
This fungal disease is very familiar to cool climate gardeners and warm climate gardeners growing low chill peaches and nectarines. Affected leaves pucker and turn brown/red. The key to control is growing strong, vigorous plants (apply seaweed, trace elements, gypsum for calcium) and using preventative fungicide sprays like copper when plants dormant or just begin to break into leaf.

Leaf spot – See also alternaria; black spot; cercospora spot/pseudocercospora spot
Leaf spot describes the affects of both bacterial and fungal diseases. Bacterial diseases often create a see-through window or holes within affected leaves. Bacterial soft rots cause by Erwinia caratovora cause lettuce to rot and spotting on Basella rubra. Erwinia and other associated bacterial diseases occur on orchids, zygocactus and other fleshy plants. Affected tissue has a terrible odour. Zanzibar Gem affected by Xanthomonas campestris develops water-soaked spots. Basil is susceptible to Pseudomonas species, while parsley is attacked by the fungus Septoria petroselini. Bacterial diseases also cause stem and root rot.

Remove the affected leaves or remove badly affected plants. Avoid watering late in the day or during cold weather. Grow seasonally appropriate vegetables and look for disease resistant varieties. Increase sunlight and avoid overwatering. Ensure plants receive balanced nutrition including calcium and potassium. Apply preventative sprays of casuarina, bicarbonate of soda and milk sprays [see Homemade pest control] or use liquid silica and potash or commercial organic fungicides based on potassium bicarbonate like Eco-Carb or Eco-Fungicide.

Erwinia on king orchid leaves (image by Julia)
Leaf Spot on Basella

Leaf spot on hippeastrum
Leaf Spot (Stagospora-curtisii) On HippeastrumsLeaf Spot (Stagospora-curtisii) On HippeastrumsRed blotch fungi (Stagospora curtisii) that attacks the leaves of hippeastrums and other bulbs indicates unsuitable growing conditions including bulbs being planted to deeply, overwatering and/or excessive shade. This disease is most prevalent during the cooler months of the year or during periods of prolonged heavy rainfall. Other bulbous plants are affected by similar conditions. Change the growing conditions to make bulbs less susceptible. Remove affected foliage.

Melanose on citrusMelanose on citrus
This disease typically affects more mature trees with foliage close to the ground. Mulch trees with a feeding mulch such as lucerne to prevent spores splashing up onto the foliage when it rains. Lift the lower branches so that foliage is well clear of the soil. Improve general tree health with additional organic nutrients and water.

Spray trees with copper-based compounds after all fruit has been harvested, thoroughly wetting the foliage, trunk and branches. Repeat applications once each year until no further evidence of disease exists. Melanose on citrus is easily confused with brown rust mites which create a similar brown discolouration of the skin, but mites are easily controlled with oil sprays.

Nematodes
Nematodes are microscopic animals found in the soil, within plant tissue and within water. Some nematodes are damaging to plants, but there are also beneficial parasitic nematodes within organic matter that control destructive nematodes. Nematodes are associated with the transfer of some plant diseases.

Root knot nematodes are the most common and obvious. They cause root galls and excessive root branching. This affects the plant’s ability to take in water and causes wilting and stunted growth. Sandy soils and those low in organic matter are prone to nematode infestation. Incorporate home made compost or composted animal manure into soil, grow nematode resistant varieties, rotate crops and pay attention to hygiene.. For severe infestations in vegetable gardens drench with black strap molasses (2 tablespoons per litre of water). Apply at planting to susceptible crops (tomatoes, potatoes, chilli and capsicum).

Nematodes
Nematodes
Root knot nematodes should not be confused with beneficial nitrogen fixing nodules common to peas, beans and other legume plants. A significant distinguishing feature is that root knot nematodes are white in colour then the nodules are broken in half. Beneficial nitrogen fixing nodules are pale pink through to pale red in colour when broken in half. Plants that form these nodules do so as a result of an association with soil organisms. This relationship enables them to convert nitrogen from the soil air into a form of nitrogen that can be used by plants. Nitrogen fixing plants are a mainstay of organic gardening. Nitrogen Fixing Nematodes

Phosphorous induced iron deficiencyPhosphorous induced iron deficiencyPhosphorous induced iron deficiency
The proteaceae family which includes grevillea, banksia, hakea and macadamia amongst others are sensitive to phosphorous. Symptoms occur six to twelve months after planting or after the application of high phosphorous products like chicken manure based fertilisers and compost and mushroom compost. Applications of iron chelates watered around the roots will provide the iron that the banksia needs. Recovery will depend on how the plant has deteriorated prior to application. Raising the soil to pH 6.5 by adding a little Dolomite lime to the soil will also help.

Phyllody on roses (image by Valerie)Phyllody
This is a flower curiosity. Roses, gerberas and other plants produce occasional abnormal flowers where leaves or even completely new stems replace petals in a bloom. A number of factors cause this deformity including latent viruses, phytoplasmas, bacterial and fungal diseases or extreme environmental conditions. Some rose cultivars are susceptible to phyllody due to their breeding genetics. Think back over the growing season and try to link the appearance of phyllody to a particular period of environmental stress and remedy this in coming seasons if possible.
Pinks Disease on citrusPinks disease
Erythricium salmonicolor or pinks disease is a debilitating fungal disease of both productive and ornamental trees. It is often mistaken for lichen. Limbs display sunken circulator patches (lichen is flat or slightly raised) often with a slight pink crusted tinge. Affected limbs are prone to dieback and decay.

High rainfall and humidity favour disease development. Prune infected branches and seal pruning cuts with tree wound dressing or a copper-based tree paste. Prune to increase air circulation and sunlight. Dispose of prunings offsite. Spray trees with a copper-based spray immediately after pruning taking care to treat the entire plant including the trunk and branched. Provided balanced nutrition to trees including adequate calcium, silica and potash. Citrus and custard apples are commonly affected.

Powdery Mildew
Powdery mildew is caused by a group of Ascomycetes fungi and affects a wide range of plants including azaleas, salvia, roses (caused by Sphaerotheca pannosa), azaleas, vegetables (especially peas and cucurbits) and fruit (especially apples and grapes). Affected growth initially looks as though it is lightly covered with talcum powder; leaves become progressively puckered and finally appear burnt. Spores are present in air and soil and tend to germinate in cool, damp or humid conditions (particularly over-night). Plants overly fed with nitrogen are more susceptible as are those grown in the shade or with poor air circulation. Avoid wetting plant foliage.

Remove affected foliage. Increase exposure to sunshine and improve air circulation around plants. Reduce use of high nitrogen fertilizer. Grow strong plants by using balanced nutrition. Apply liquid seaweed; bicarbonate of soda, milk or casuarina spray [see Homemade pest control], wettable sulphur, dusting sulphur or commercial liquid silica and potash. Potassium bicarbonate sprays like Eco-Carb or Eco-Fungicide are also effective. Yellow, mildew eating lady bugs (Illeis galbula) and their larvae eat powdery mildew and assists in controlling the disease.

Powdery Mildew on roses
Mildew on peas

Rust
Rust describes a group of fungal organisms that cause rust-like lesions on foliage. Initial symptoms appear as white, yellow, orange or brown pustules on the undersides of the foliage, progressing to circular yellow leaf markings on the top sides of leaves, followed by leaf drop. The disease worse during periods of high humidity, mist and rain, because spores need moisture to germinate.

Spores travel through the air and also via water splash. Plants may be infected without showing symptoms, then suddenly deteriorate when conditions change. Rust diseases often attack a single host plant or group of related plants. Rust on one plant will not necessarily infect neighbouring plants of a different species. Rust affects roses (Phragmidium tuberculatum); canna (Puccinia thaliae); day lilies (Puccinia hemerocallidis) and geraniums (Puccinia pelargonii-zonalis) are particularly prone to rust. White rust on spinach results from infection by Albugo occidentalis and causes raised white rust pustules on spinach leaves. Remove the infected leaves. Remove infected leaves, avoid overhead watering; improve air circulation and exposure to sunshine. Commercial potassium bicarbonate sprays like Eco-fungicide may provide some protection for susceptible plants.

White rust disease
White rust
Frangipani RustRust on frangipani
Infected frangipani plants develop bright yellow rust pustules on the undersides of leaves. This detracts from the appearance of plants and causes premature leaf drop. Frangipani trees that are severely affected year after year can be weakened, but the disease is rarely fatal. Rainfall and high humidity increase the incidence of the disease. Plants grown in warm north facing, full sun positions are less susceptible. Protective copper-based sprays can be applied when trees first come into leaf, but are largely ineffective if conditions favour the disease or once rust symptoms become evident. Collect and remove fallen leaves. Neighbouring trees that are infected will provide a wind borne source of fungal spores.

Lawn rust (image by Michael)Rust on lawns
Puccinia fungi cause rust on lawns. Susceptibility increases when growth slows and humidity or soil moisture levels are high. Reduce lawn watering. Add gypsum to improve the drainage. Increase available sunlight to lawn where possible by pruning trees causing shading. Avoid high nitrogen fertilizer applications during periods of slowed growth. Lawn rust is generally not fatal and will disappear when the conditions change. Applications of potassium bicarbonate based sprays like Eco-fungicide may help.

Myrtle rust (Austropuccinia psidii)Rust on myrtaceae – Myrtle rust (Austropuccinia psidii)
This exotic fungus was first detected in NSW during 2010. The spread of rust spores is almost impossible to control and attempts to eradicate myrtle rust have failed. This disease potentially affects all native myrtaceae including eucalyptus, callistemon, Chamelaucium uncinatum (Geraldton wax), melaleuca, tea tree, backhousia etc. Commercial growers manage this disease with strict nursery protocols and fungicide sprays. Propagation of naturally resistant plants is the focus of commercial operations. Home gardeners should be prepared to accept some damage particularly during hot, humid weather. Remove highly susceptible species.

Scab
Scab describes the appearance of several different fungal diseases that create crusted lesions on a range of fruiting and edible crops. Citrus, mango, passionfruit and potatoes are particularly susceptible.

Citrus ScabScab on citrus
This fungal disease potentially attacks all citrus, but lemons are most susceptible. The disease does not really affect fruit flesh, but the rind is unattractive and fruit often become mis-shapen. Where infestations are severe, the foliage may also develop scab lesions. Prune off and dispose of infected fruit; clean up fallen fruit and prune twiggy and dead growth that harbours fungal spores. Improve the health of the plant by supplying additional nutrition and spray trees with copper-based products after fruit harvest to control outbreaks.

Scab on mango is caused by the fungus Denticularia mangiferae causes shot hole effect on leaves and lesions on fruit. Rainfall and high humidity increase the incidence of the disease. Take preventative action by pruning to improve air circulation and applying balanced nutrition.

Passionfruit ScabScab on passionfruit
Cladosporium oxysporum results in passionfruit and granadilla developing scab encrusted lesions on fruit. Heavy infestations (like the one pictured) cause fruit to shrivel and drop prematurely. Vines grown in shaded areas and those allowed to grow to thickly are susceptible. Always grow vines in full sun. Prune and train vines to improve air circulation. Avoid wetting the leaves. Remove and dispose of infected fruit (offsite). Look for resistant varieties. Take preventative action by applying a copper-based fungicide. This disease may be confused with the fungus disease Septoria passifloricola, but preventative actions are similar.
Potato scabScab on potatoes
This fungal disease is commonly introduced by using non-certified seed potatoes (or saving seed from previous crop) and is worse in alkaline soil and dry conditions. Prepare a new area for your potatoes, ensure the pH is not above 6, use certified disease free seed potatoes and rotate crops each season. Potatoes, tomatoes, capsicum and eggplants are related crops and should not be planted after one another in the same garden bed. Certified disease free seed potatoes are available from nurseries, produce stores or online.

Sooty MouldSooty Mould
Insects with piercing and sucking mouthparts like scale, aphids and mealy bugs plus ants that protect and feed on their secretions are commonly associated with sooty mould. Sooty mould is a black fungus that grows on the secretions produced by insects and will disappear once the insects that produce these secretions are controlled. Citrus, gardenias, lillypilly hedges and fine leafed native plants are susceptible.

Use baits and repellents to control ants. Manually remove heavy infestations of sucking pests like scale from stems with a nail brush. Apply three applications of home made [Do It Yourself Controls - Oil Spray] or commercial oil sprays at fortnightly intervals. Dilute to half strength on fine leaf natives or plants with hairs on the leaves. Home made [Do It Yourself Controls] and commercial soap sprays can be used on plants sensitive to oil sprays, but should be used twice a week for six weeks.

Stylar End RotStylar End Rot
This disease affects Tahitian limes and occurs when fruit is left to over-ripen on the tree. The base of the fruit develops a soft rot as the internal flesh begins to break down. Fruit eventually falls to the ground. The internal flesh also shows deterioration when cut. Fruit should be harvested while still green in colour prevent this occurring. Fruit should be harvested and stored under refrigeration, rather than leaving it to hang for excessively on periods on the tree.

Target Spot on TomatoesTarget Spot
This disease affects a range of plants, but tomatoes are particularly badly affected. Some varieties are more susceptible than others and wet conditions (especially rain or overhead watering) invite disease outbreaks. Build strong healthy grow by adding gypsum (to supply calcium) and trace elements to soil or potting mix at planting and applying liquid seaweed during the growing season. Eco-fungicide and copper-based fungicides can help limit outbreaks. Train plants up to improve air circulation around the foliage. Do not let the lower foliage come in contact with the soil and prune off and dispose of affected leaves. Deterioration of the lower leaves of tomatoes is to be expected during the lifespan of a tomato. These leaves represent natural aging and should be removed.

Zucchini VirusVirus
Virus diseases are transferred via infected seed, cuttings and grafting and by aphids or other sucking insects. To avoid this problem, never save seed from plants that show poor growth or other symptoms that may indicate potential disease problems. Remove and destroy infected plants to prevent the possible spread by insect vectors to neighbouring plants. Where possible plant only certified seed potatoes and virus free strawberries.

Virus diseases in plants often present as angular leaf yellowing and poor growth. Some latent viruses do not show obvious leaf symptoms, but affect growth and productivity (potatoes). Cucurbits are particularly prone to virus diseases, but they also occur in roses and camellias.

Passionfruit VirusWoodiness virus on passionfruit
Affected vines show characteristic mosaic leaf yellowing. This disease is often present in plants from an early age, but only begins to gain the upper hand when the vine becomes productive or is stressed in some way. Affected vines may continue to grow, flower and fruit, but will always lack vigour. There is no cure for virus affected plants. Remove vines. Given their rapid growth rate, high productivity and short lifespan, passionfruit vines should be replaced every few years. Plant new vines in a different part of the garden.

Wilt
The fungus Fusarium oxysporum is a common cause of wilt disease. This disease is persistent in the soil and can be introduced via contaminated plants or seeds. Tip dieback and death of susceptible species is common. Cutting stems of suspect plants longitudinally reveals discolouration associated with blocking of the vascular or water conducting tissue in plants. Choose disease resistant varieties. Avoid saving seed from plants that die prematurely or are otherwise suspected of suffering from disease.

Please note plants also wilt and die from overwatering, attack by root knot nematodes, attack by curl grubs or use of overly rich manure and/or excess fertilizer.

Vivipary/Pseudo vivipary on strawberriesVivipary/Pseudo vivipary on strawberries

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