Powdery mildew: a threat to most cucurbit species

This widespread disease, which grows well in environments with high humidity, can reduce yield significantly, warns Bill Kerr.

- Bill Kerr.

Powdery mildew, a fungal disease, appears relatively late in the season and can do much damage once established. As plants get older, they become more susceptible.

One of the problems with this disease is that it quickly develops resistance to crop fungicides, thanks to its rapid life cycle. Resistance is hastened when a farmer discovers a fungicide that is effective and then uses it exclusively. If just one spore out of the millions circulating in an area has resistance to the product and reproduces, the product will no longer be effective in that area.

The solution is to alternate products with different modes of action; this will enable the current product to kill off the odd spore that has developed a resistant gene to the previous product.