Air entrainment samples of volatiles from panicles of intact wheat, Triticum aestivum, cultivar 'Lynx' were collected at the ear emergence/early anthesis growth stage. In an olfactometer bioassay, both freshly cut panicles and an air entrainment sample were found to attract female orange wheat blossom midge adults, Sitodiplosis mosellana. Coupled gas chromatography-electroantennography (GC-EAG) analyses of panicle volatiles located six electrophysiologically active components. These were identified by coupled gas chromatography-mass spectrometry and coinjection with authentic standards, on polar and nonpolar GC columns, as acetophenone, (Z)-3-hexenyl acetate, 3-carene, 2-tridecanone, 2-ethyl-1-hexanol, and 1-octen-3-ol. Although none of these was active when presented individually at the levels present in the entrainment sample, acetophenone, (Z)-3-hexenyl acetate, and 3-carene were active in the olfactometer when presented at a higher dose of 100 ng on filter paper. However, the six-component blend and a blend of acetophenone, (Z)-3-hexenyl acetate, and 3-carene, in the same ratio and concentration as in a natural sample, was as attractive to female S. mosellana as the whole air entrainment sample.

No abstract

Field-trapping experiments with synthetic 2,7-nonadiyl dibutyrate, the female-produced sex pheromone of the orange wheat blossom midge, Sitodiplosis mosellana (Géhin), demonstrated that pheromone traps were highly attractive to males and caught very few non-target organisms. Different formulations of pheromone were tested to identify the optimum release rate and dispenser type for use in pheromone traps in the UK. Key findings were that racemic pheromone was as effective as enantiomerically pure (2S,7R)-2,7-nonadiyl dibutyrate, that release rates higher than 0.5 µg day −1 were not necessary and that the optimal formulation was a 1 mg pheromone loading in a rubber septum. Pheromone traps gave a reliable indication of peak midge emergence, onset of flight and abundance of midges throughout the season. A strong correlation between maximum trap catch and crop infestation levels was obtained.

The economics of control of grain aphid (Sitobion auenae) and rose-grain aphid (Metopolophium dirhodum) were investigated in a series of experiments carried out across England in 1988 and 1989. Sprays of pirimicarb or dimethoate were applied at three growth stages and yield effects measured. Aphid infestations were determined by a range of different methods, to evaluate the value of each for decision making.Aphids overwintered in crops in mild conditions in both seasons, resulting in early population build-up and decline in many cases. Aphicide sprays applied during the booting stage increased average yields by 0.26 t/ha. Profitability of the treatment strategies considered was not greatly enhanced by selective spray application related to aphid assessment at this stage. Delaying decision making to the flowering or grain-filling stages resulted in reduced profitability. A poor correlation between aphid numbers and crop yield response to sprays was found. This was shown to be due to differences in subsequent aphid population development and in aphicide efficacy. Grain quality was affected only by high aphid infestations which caused large yield reductions.

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...