Low temperature mortality of cereal aphids.
The experiment, run between January and March 1979, was designed to provide quantitative data on the relative importance of rain, snow, high winds and sub-zero temperatures as mortality factors acting on S. avenae and M. dirhodum virgincparae overwintering on winter wheat. The aphids were exposed on winter weat growing in pots in the field. The pots had a narrow, sticky barrier round their rims to exclude predators, and were sunk into the ground in a plot of winter wheat planted in early October. Similar batches of aphids were exposed one after the other and the mortality each experienced was related to the weather conditions during the period of exposure. Each batch was assessed after four days' exposure and again four days later, and was then replaced by a fresh batch. The aphids used were cultured at 20o ± 1½oC and acclimated at 6½oC for six days. (Only medium-sized nymphs ( 1.1 - 2.2 mm) were used.