Warm and wet spring conditions are ideal for the development of fungal diseases in vegetable crops.

Late blight (Phytophthora infestans), renowned for causing the Irish potato famine, is still one of the most significant fungal diseases in potatoes. It causes darkly coloured, irregularly shaped lesions on leaves which quickly grow to result in blackened leaves hanging on stems. Infection occurs when relative humidity is high (95 to 100 percent) and temperatures are between 12°C 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.

The most significant foliar disease in alliums, downy mildew (Peronospora destructor, pictured) 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°C and 16°C promote spore germination and increase infection. During these conditions, implement a preventative fungicide programme using systemic products typically starting around the four to five leaf stage. Zorvec Enicade has performed well in Fruitfed Research and Development trials¹, showing strong control of downy mildew. 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 to help control Stemphylium in onions.

Always consider resistance management when selecting fungicides to control these diseases, and talk with your Fruitfed Technical Horticultural Representative for assistance with fungicide selection.