Effects of fall and early spring populations of the grain aphids Schizaphis Graminum (Rondani), Rhopalosiphum padi (L.), R. maidis (Fitch), and Microsiphum avenae (F.) on winter wheat and winter barley production were evaluated in field trials and in state cultivar trials in eastern Virginia. Data collected in field tests where aphids were controlled with systemic insecticides (disulfoton, carbofuran, or dimethoate) revealed significant yield increases compared with the untreated plots in 1980 and 1983 when aphid populations at time of application were >20 per 0.3 m of row. Barley yellow dwarf virus (BYDV) infection was>10% of total untreated plot area in 1980 and 1983. No reductions in grain yields were noted in 1981, 1982, and 1984, years when aphid populations were very low (<1.3 per 0.3 m of row) and no BYDV symptoms were present. Yield increases were observed in the wheat and barley cultivar trials in 1980 and 1983 when early spring applications of disulfoton 15 G were made; no differences were noted in 1981 and 1982 when the same insecticide application was made. ‘Tyler’ wheat had relatively high yield increases in the treated plots during all four seasons, even when aphid populations were very low. ‘Massey’ had lower yield increases in the treated plots than most of the 30 cultivar entries each year. ‘Barsoy’ and ‘Maury’ barley also had lower yield increases in the treated plots than the other 20 cultivars being evaluated in 3 of the 4 years tested.
No takes yet. Share an insight, caveat, or question.
McPherson et al. (1986) studied this question.