Fungal, bacterial and virus diseases seem to occur at any time although some flourish in summer while others prefer the wet conditions of winter.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
In the battle against these pests and diseases we tend to reach for a chemical solution and, while these are sometimes necessary, there are a number of things we can do to lessen these outbreaks.
One is crop rotation which is a system of planting where crops, subject to the same disease, don’t follow each other.
Carrots and parsnips shouldn’t be planted too close in the rotation to the tomato family because they are often attacked by root-knot nematodes.
Marigolds are claimed to reduce the population of root-knot nematodes as does planting and digging in a green crop of mustard.
Onions grown before potatoes help to clean up the fungal disease Rhizoctonia which is a soil-borne fungus that causes damping-off and root and stem rots.
When watering pumpkins, cucumbers and zucchinis keep the leaves dry by watering to the base of the plants. This reduces the chances of powdery mildew which appears as a powder-like coating that develops on the leaves and stems.
It’s a good practice to water early in the day so plants have a chance to dry out before the evening. Powdery mildew can attack a wide range of other plants including roses.
Certain soil conditions favour the development of some disease. Root rot, where the root system becomes infected and rotten, is usually associated with over watering, poor drainage or prolonged wet spells.
Once established, the disease is almost always lethal and an affected plant may die suddenly.
Often the disease is caused by a pathogen called Phytophthora, which travels through the soil water. Plants from dry climates should always be grown in well-drained conditions which may mean planting them either in a container or a raised bed.
Poorly drained, acid soils are ideal conditions for club root in cabbages. Improved drainage and an addition of lime should remedy this problem.
A green manure crop dug into the ground before planting beans is said to reduce fusarium wilt.
The position vegetables grow in is important. Onions should be grown in an open sunny spot to help prevent downy mildew.
Crops that are crowded together are more likely to suffer from attacks of grey mould which is a fungus disease that usually enters through a wound or infects plants that are stressed.
Debris such as dead leaves and stems is where grey mould overwinters ready to start its cycle the following spring.
Keep the garden area clean and tidy. When pruning always collect prunings and any diseased leaves bin immediately as pests can overwinter on these.
To help minimise these fungal and bacterial problems copper oxychloride and Bordeaux mixtures are quite effective.
Sulphur is an excellent fungicide that controls mites as well as powdery mildew. Avoid spraying on hot, humid days as leaf burn may occur. There are many products available at nurseries so ask for advice if you are unsure about which one to use.
If you do have to use any chemical products always read the instructions carefully before use and check to see if there is a withholding period before you can consume vegetables and fruit.
Diary
November 26-27: Blenheim Gallery & Garden is holding an ‘Artist’s Garden’ exhibition this weekend at 733 Cressy Road, Longford from 10.30am to 4.00pm. Adults $8, under 16 free.