This is a common fungal disease for squashes, especially in dry conditions when plants are under stress. You will see white, powdery patches of fungus on leaves, stems and in severe case, the fruits.
- Mulching and watering reduces water stress and helps make plants less prone to infection.
- Promptly removing any infected shoots will reduce subsequent infection.
- There are no chemicals to treat powdery mildew, but you can use plant and fish oils as a preventative.
- A study in 1999 using Milk Sprays at 40% milk and 60% water have been proven to prevent Powdery Mildew, this is best sprayed every 10 days on a sunny afternoon for best results.
No fruit, or fruit rotting when very small: This is a physiological problem, caused by the growing conditions, not a pest or disease. It is a problem when the weather in early summer is cool and this causes inadequate pollination.
This is usually a temporary problem and once the weather starts to improve, so will pollination. You can try to hand-pollinate plants yourself by removing a male flower (they don’t have a swelling at their base) and brushing the central parts against the centre of a female flower (female flowers have a swelling at the base – this is the beginning of the fruit). But this is a bit of a hassle, and normally the plant will correct this problem itself.
This is a problem normally in wet conditions and is usually worse on weak or damaged plants. The mould usually enters through a wound, but under the right conditions even healthy plants will be infected. You will see fuzzy grey mould on affected buds, leaves, flowers or fruit. Infected plant parts eventually shrivel and die..
Hygiene is very important in preventing the spread of grey mould. If you see grey mould, remove the infected material and destroy. Grey mould is encouraged by overcrowding, so make sure you plant your pumpkins at the appropriate distance apart. No fungicides are approved for use by amateur gardeners against grey mould. Products containing plant and fish oil blends may be used but are unlikely to have much impact.