• Pest Type: Disease
• Crops Affected: Wheat, winter, Wheat, spring, Wheat, Rye, Oats, Barley

Symptoms
Early infections cause yellowing of leaf tips. Yellowing then moves down the leaf along the margins, usually with a green strip in the middle. Later yellow turns to bronze and in oats a red colour usually occurs. Infected leaves may be stiffer than healthy leaves. Severely affected plants are stunted. Infections may first appear on single plants but are usually in small patches. Symptomless infections which affect plant yield can also occur and these can be detected only by laboratory analysis. Yield loss occurs because infected plants produce fewer heads and shrivelled grain, and in severe early infections no grain.

Disease Cycle
The virus causing yellow dwarf exists in several strains which are transmitted by many species of aphid. Initial infections occur when aphids carrying the virus come in from further south in the continent. Once established the aphids spread the virus locally. The disease is not seed-borne nor does it survive in overwintering aphid eggs.

Control Measures
There are relatively good guidelines for managing aphids in wheat. Delaying planting (using the Hessian Fly Free Date) is an important and reliable tool. That date is based on the first hard frost, which kills large numbers of soft-bodied insects, including aphids and Hessian flies. Plant varieties that are not highly sensitive to BYDV. The most important time for controlling aphids to prevent BYDV is during the first 30 days following emergence. Consult local advisers concerning threshold levels and best control measures in your area. In some regions, as few as 3 aphids per foot of row during the first 30 days after emergence may justify using an insecticide.