Technical advice for controlling vegetable fungal diseases
Several fungal diseases have the potential to develop in vegetable crops as spring brings warmer and wet conditions.
The potato fungal disease, late blight (Phytophthora infestans, pictured) can devastate crops if left unchecked. It causes darkly coloured and irregularly shaped lesions on leaves which quickly result in blackened leaves hanging on stems. Infection occurs when relative humidity is high (95 to 100 percent) and temperatures are between 12 and 26°C. When infection conditions are ideal, a white fungal growth can be found around lesions. When conditions favour infection, use a preventative fungicide programme with systemic products.
Downy mildew (Peronospora destructor) is a significant disease in the Allium family (onions, garlic, leeks and shallots). It causes pale yellow or light green, oval shaped lesions on leaves. In humid conditions, lesions show masses of grey fungal spores before turning brown and causing leaves to collapse. Periods of dew with temperatures between 7 and 16°C promote spore germination and increase infection. During these conditions, implement a preventative fungicide programme using systemic products starting around the four to five leaf stage. Zorvec® Enicade has performed well in Fruitfed Research and Development trials1. Use preventatively before switching to an alternative, robust, systemic fungicide to aid resistance management.
Downy mildew lesions allow Stemphylium vesicarium to infect a plant. By controlling downy mildew effectively, growers can also help control Stemphylium. This disease infects onions through damage caused by herbicides, hail or thrips, or factors such as heat stress. Apex® and Foscheck® are registered options.
Always consider resistance management when selecting fungicides to control these diseases, and talk with your local Fruitfed Technical Horticultural Representative for assistance with fungicide selection.
ARTICLE WRITTEN BY DANIEL SUTTON, TECHNICAL SPECIALIST – VEGETABLES
AVCM registration numbers: Apex® P009012, Foschek® P004555, Zorvec® Enicade #P009225. Read the registered label before use.
1 Multiple trials in Pukekohe by Fruitfed Supplies Technical Team.