2 3 4
SummaryField experiments on the use of recommended and reduced application rates of aphicides for control of summer aphid infestations on winter wheat have been done at five sites each year from 1990 to 1992. The experiment compared sprays of pirimicarb at recommended rate (140g a.i. ha-') and reduced rate (25 g a.i. ha-') and of alphacypermethrin at recommended rate (15 g a.i. ha-') and one third recommended rate (5 g a.i. ha-'), each applied either at flag leaf emergence or at flowering. Aphid infestations were allowed to develop naturally and were measured at critical growth stages. In 1990, overwintered aphid infestations, together with established populations of parasitoids, were detected at four of the five sites when the first assessment was made in April. Parasitoids provided sufficient aphid control to prevent yield loss at two sites without pesticide applications. At three sites both aphicides gave similar levels of control and yield response at both recommended and reduced application rates. In 1991 and 1992 no overwintered aphids were detected in the crops and aphid infestations developed much later. Aphicide applications gave significant yield responses at four sites in 1992, Recommended rates gave better control of aphids than reduced rates. There was no significant difference in the yield response obtained with different rates of aphicide. Lee G, Mann B P, Wratten S D. 1991. A computer-based advisory system for cereal aphidsfield testing the model. Annals of Applied Biology 118:503-512. Mann B P, Wratten S D, Poehling M, Borgemeister C. 1991. The economics of reduced-rate insecticide applications to control aphids in winter wheat. Annals of Applied Biology 119:451464. Oakley J N. 1992. Development of an integrated control strategy for summer aphids in winter wheat. . 1994. A field evaluation of different criteria for determining the need to treat winter wheat against the grain aphid Sitobion avenue and the rose grain aphid Metopolophium dirhodum. Annals of Applied Biology 124:195-211. Oakley J N, Ellis S A, Walters K FA, Watling M. 1993. The effects of cereal aphid feeding on wheat quality. Aspects of Applied Biology 36, Cereal Quality Ill, pp. 383-390. Oakley J N, Wratten S D, Dixon A F G, Carter N. 1988. The biology and control of cereal aphids. Research Review No. 10. London: Home-Grown Cereals Authority. Poehling H M. 1987. Effects of reduced dose rates of pirimicarb and fenvalerate on aphids and beneficial arthropods in winter wheat. Bulletin SROP 10:75-83. Powell W, Dean D J, Bardner R 1985. Effects of pirimicarb, dimethoate and benomyl on natural enemies of cereal aphids in winter wheat. Annals of Applied Biology 106:235-242. Purvis G, Carter N, Powell W. 1988. Observations on the effects of an autumn application of a pyrethroid insecticide on non-target predatory species on winter cereals. In Integrated Crop Protection in Cereals, pp. 153-166. Eds R Cavalloro and K D Sunderland. Rotterdam: A A Balkema. Tottman D R 1987. The decimal code for the growth stages of cereals, with illustrat...