Evaluating the timing of insecticide application to manage barley yellow dwarf virus and yield in winter barley

Abstract

Barley yellow dwarf virus (BYDV) is an important viral disease of grain crops worldwide and a major cause of yield loss. The risk periods for BYDV infection coincide with milder temperature that prolongs aphid flight and facilitates viral transmission through primary and secondary aphid movement in the crop. Secondary aphid movement is associated with greater BYDV spread in winter cereals. A critical component of BYDV management is therefore delaying sowing of winter cereals and correctly timing insecticide application to maximise crop protection. Previous research in Ireland considered insecticide timing in early (September) and late (October onwards) sown cereals. Early research did not consider action thresholds around temperature, aphid flight and risk of secondary spread. This research set out to understand the optimal timing of insecticide application in October sown winter barley to reduce BYDV infection and yield impact. A critical temperature of 3°C was used as a threshold for aphid development that leads to movement and BYDV spread, and insecticide treatments were applied to the crop at predictable intervals in relation to temperature. Results show that BYDV symptoms and yield are affected by spray time, location and year, although only significant with regard to the reduction of BYDV symptoms. For both BYDV symptoms and yield, there was a significant difference between untreated (control) plots and “early” and “late” applications of insecticide, again more notable for BYDV symptoms than yield. This work indicates the value of optimising a single insecticide spray for control of October sown cereals and supports decision-making in the management of cereal crops.