The effect of temperature and wind on the flight activity of cereal aphids

SUMMARY The lower temperature threshold for take‐off inSitobion avenaeobtained from an analysis of daily 12·2 m suction trap catches was 16°C. In the laboratory, the take‐off threshold forS. avenaewas 17·5°C in increasing temperatures, but 19°C when aphids were kept at constant temperatures for a short period of time. The equivalent thresholds were both 20·5°C forMetopolophium dirhodum.Over a period of 16 h noS. avenaetook‐off from plants at 10°C, 70% at 15°C and all within 16 h at 20°C. It was concluded that suction trap catches can be used to compare the temperature thresholds for take‐off of both different species and morphs of a species of aphid. Emigrants ofRhopalosiphum padi, but not ofM. dirhodum, took‐off at a higher temperature than the alate exules. High winds were found to delay but not inhibit take‐off both in the field, and in the laboratory, using both artificial and plant substrates. All aphids eventually flew, even from favourable hosts. It was concluded that adverse weather conditions will delay but not prevent cereal aphid migration in early summer.