Downy mildew is common but seldom causes severe damage. It is favored by cool and wet or humid weather. Leaves turn light green to yellow, and appear twisted and curled. The tops of shoots often become dwarfed. A fine, grayish to violet fungal growth can be seen on the underside of affected leaflets.
Downy mildew is most likely to be a problem in the spring.
Varieties with resistance to downy mildew are available. Contact your district agriculturist for information on resistant varieties. If mildew is severe in the spring, do not delay the first cut. Harvesting removes most of the infected tissue and reduces the humidity in the crop canopy. Warmer summer temperatures will reduce the chance of mildew damage to the regrowth.