Picture The Disease
[Black Spot on
End Rot] [Black Spot] [Citrus Melanose] [Citrus
Scab] [Damping Off]
[Fleck] [Frangipani Rust]
[Mildew on Peas] [Passionfruit
Leaf Curl] [Phosphorous
induced iron deficiency] [Potato
Knot Nematodes] [Rose
End Rot] [Target
Anthracnose is the primary reason
why mangoes, avocadoes and some other fruit trees fail to fruit or develop
blackened fruit that drops prematurely. Anthracnose is a
fungal disease that is exacerbated by rain and high humidity. During dry
weather the disease is virtually absent.
of copper based sprays immediately prior to flowering and during early fruit set
and/or use of biodynamic preparations such as casuarina tea [see Do It Yourself Pest Control] can help reduce the effects of
anthracnose. Some fruit tree varieties also possess inherent resistance to
Spot on Pawpaw
Adequate nutrition is as much
a tool in disease control as the use of sprays.
Plants deficient in potassium, phosphorous and magnesium
are more susceptible to attack by black spot and powdery
mildew. Simply increasing the potassium (sulphate
of potash and/or lucerne mulch), phosphorous
(rock phosphate or chicken manure) and
magnesium levels (Epsom salts) helps to make plants more
resistant to disease. Pawpaws are most susceptible to
black spot disease during the cooler months. Spraying
with sulphur or copper based compounds prior to the
onset of the cool weather and watering with liquid
seaweed can help reduce the severity of infestations.
Black Spot on Roses
Ensure plants receive balanced nutrition (see above). Foliage applications of seaweed sprays are recommended, not so much for their nutritional value, but for their ability to increase disease resistance in plants. Foliage applications of liquid potash are also beneficial. Bicarbonate soda sprays
may be used. [Do
It Yourself Controls -
Black Spot Spray]. Fishmeal and other fish-based fertilisers
contain trace elements valuable in building disease resistance. Remove old canes and diseased wood as this harbours bacterial and fungal spores, insects and mites. Old wood is also less efficient at transporting water and minerals and therefore produces less vigorous growth, fewer flowers and is more disease prone.
Potassium bicarbonate sprays in the form of Eco-Rose
will bring about control when used regularly and combine
with a small amount of an oil-based spray to help it to
adhere to plant foliage.
This disorder has two contributing causes - calcium
deficiency and irregular watering. When planting
tomatoes, always add calcium in the form of gypsum
(powdered or liquid form) or if the pH of the soil is
acid, apply Dolomite lime. Ensure that tomatoes are
watered regularly rather than allowing them to dry out
before rewatering. Affected fruit cannot be saved, but
if plants are affected early in the growing season, it
is possible to apply calcium and improve watering
practices to save fruit produced later in the season.
This disease typically affects more mature trees or plants that have a canopy of foliage that hangs close to the ground. Mulch trees with a feeding mulch such as lucerne. This will help to prevent spores splashing up onto the foliage when it rains. Lift the lower branches so that foliage is well clear of the
soil. Spray trees with copper-based compounds after all fruit has been harvested, thoroughly wetting the foliage, trunk and branches. Repeat applications each year until no further evidence of disease exists. Improve general tree health with additional
organic nutrients and water.
This fungal disease potentially attacks all citrus, but
lemons are most commonly affected. This disease does not
really affect the flesh of the fruit, but the rind is
unattractive and the fruit often become mis-shapen.
Where infestations are severe, the foliage may also
develop scab lesions. Improving the health of the plant
by supplying additional nutrition and sprays trees with
copper-based products after the fruit is harvest will
control outbreaks. Prune off and dispose of infected
fruit, clean up fallen fruit and prune old twiggy growth
that harbours fungal spores.
Damping off fungus
This disease 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 clean compost. Wash all pots and tools in hot, soapy water then allow to dry in the sun before use. Make sure that plants do not sit in water. There is no cure for affected plants and they should be disposed of so as not to infect neighbouring stock.
Note that newly planted seedlings can appear to suffer from a similar condition, but this is typically the result of over watering or planting into a soil containing excessive amounts of fertiliser or overly rich compost and manure.
The fleck disease (Fabraea maculata) shown here is a
fungal disease that attacks pome or pip fruit like
apples, pears and quince trees. This disease causes
serious defoliation and tip dieback, weakening the tree,
negatively affecting flowering and fruiting . It also
disfigures and marks fruit. Some varieties are more
resistant to this disease than others, so ask your local
nursery and choose varieties best suited to your region.
While the disease become most apparent over summer,
preventative sprays applied during winter and/or at
first bud burst are an important control measure. Copper
sprays and usually recommended, but equally important is
the use of seaweed products and increasing silica and
potassium levels in plants to aid their disease
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. Protective copper based sprays can be applied when trees first come into leaf, but are largely ineffective once rust symptoms become evident. Fallen leaves provide a source of infected material. Collecting and removing fallen leaves is one strategy to reduce infection. Any neighbouring trees that are infected will provide a wind borne source of fungal spores.
Mildew on Peas
Powdery mildew affects a range of edible and ornamental
crops. The spores of this disease are present in air and
soil and tend to germinate in cool, 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. Grow strong plants
by using balanced nutrition and applying liquid seaweed.
Apply wettable sulphur or potassium bicarbonate sprays
like Eco-Rose or Eco-Fungicide.
This disease is caused by a Cladosporium fungus. It
results in the fruit of passionfruit and granadilla
developing scab encrusted lesions. Heavy infestations
(like the one pictured) cause fruit to shrivel and drop
prematurely. Many other types of fruit and vegetables
are affected by this disease. Vines grown in shaded
areas appear to be more susceptible. Complete
eradication is difficult in these situations, so always
grow vines in full sun. Remove and dispose of infected
fruit (offsite). Spray vines thoroughly with a copper
At the end of the growing season after production of a bountiful crop, passionfruit vines can look tired and in need of a well-earned rest. In some cases, vines will show characteristic mosaic leaf yellowing that indicates presence of a virus disease. Such diseases are often present in plants from an early age, but only begin to gain the upper hand when the vine is occupied with fruit production or stressed in some way. Affected vines may continue to grow, flower and fruit in coming seasons, but will always lack vigour. Unfortunately there is no cure for virus affected plants. Given their rapid growth rate, high productivity and short lifespan, passionfruit vines are best replaced every few years.
Cool climate gardeners are very familiar with this
disease, but with more warm climate gardeners growing
low chill peaches and nectarines, calls to gardening
talkback about this disease are increasing. This fungal
disease causes the leaves to 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.
induced iron deficiency
ABC Gardening Talkback
listener Tony of Lota sent this image of his Banksia integrifolia. Tony writes, 'A lot of the new leaves are
yellow rather than dark green, and there is dieback of
new growth. I have dug holes to about 700mm and filled
them with compost, which has a pH of 5.5.' All
banksias are sensitive to phosphorous and this banksia
is suffering from the classic symptoms of phosphorous
induced iron deficiency. This means that the phosphorous
in the soil (found in the compost Tony added) have
caused iron to become
unavailable to the plant. Symptoms typically occur six
to twelve months after planting or after the application
of other high phosphorous products like chicken manure
based fertilisers or 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.
Potato scab is a disease 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. Remember that
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.
Root Knot 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 nematodes found within organic matter that parasitise destructive nematodes. Nematodes that attack plant roots are the most common. They cause root galls and excessive root branching. This affects the plant’s ability to take in water and nutrients,
wilting and stunted growth. Sandy soils
are particularly prone to nematode infestation. Control can be achieved by incorporating organic material into the soil, growing nematode resistant varieties, crop rotation and paying attention to hygiene procedures. For severe infestations you can treat vegetable growing areas with a mix of molasses (2 tablespoons per litre of water). This should only be used on areas that will grow nematode susceptible crops (tomatoes, potatoes and capsicum). Do not use across the entire vegetable garden as this mix has the potential to kill worms.
From time to time roses may produce
abnormal flowers where leaves or even completely new
stems (as in this image from Valerie Zwart) replace
petals in the rose bloom. This flower abnormality is
known as phyllody. A number of factors can cause this
deformity including latent viruses, phytoplasmas,
bacterial and fungal diseases or extreme environmental
conditions. Some rose cultivars are more susceptible to
phyllody than others due to the genetics of their
breeding. Think back over the past season and decide if
you can link the odd appearance of the rose to a
particular period of environmental stress (and remedy
this in coming seasons if possible) or simply regard you
phyllodic roses as a curiosity.
Scale insects and their associated sooty mould are common pests of many plants including citrus, gardenias, lillypilly hedges and other native plants. Conventional oil based controls, see [Do It Yourself Controls - Oil Spray] can be used, but should be diluted to half strength on fine leaf natives or plants with hairs on the leaves. Avoid using oil based products on plants with grey foliage. Commercial
oil sprays include Eco-Oil, Healthy Earth Plant Spray
and Eco-Neem. Soap sprays are also effective, but must be used on a regular basis. Pyrethrum based products can also be used.
Stylar End Rot
This disease affects
Tahitian limes and occurs where fruit is left to over ripen on the tree. The base of the
fruit develops a soft rot and fruit fall to the ground. The internal flesh also
shows deterioration when cut.
Fruit should be
harvested while still green in colour prevent this occurring.
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) tend to make the conditions
worse. Build strong healthy grow by giving plants
regular doses of liquid seaweed, trace elements and
gypsum (to supply calcium). 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.
This zucchini plant is showing symptoms of virus diseases. Virus diseases can be transferred from one generation to the next via infected seed and between garden plants by aphids or other sucking insects. To avoid this problem, never save seed from any plants that show poor growth or other symptoms that may indicate potential disease problems. Remove and destroy infected plants to prevent the possible spread of the disease to neighbouring plants.
Top of Page
© Copyright Annette McFarlane 2007-2016 All Rights Reserved