Effects of sustained immobilisation on aphids

Immobilisation of aphids of three species, Schizaphis graminum, Myzus persicae and Dactynotus ambrosiae, was accomplished using low temperature (6 ± 1°C; or nitrogen (N₂), argon (Ar), or carbon dioxide (CO₂) gases at 25°C for 1,3,6, or 24 h. Mortality was recorded and also times until treated aphids first walked or probed. Cold immobilisation caused least mortality and allowed rapid recovery of walking and probing abilities. CO₂ treatment, even when accompanied by cyclic administration of bottled air, caused excessive mortality when used beyond 6 h, and long recovery times. After 24 h immobilisation with CO₂ aphids seldom walked or probed. N₂ or Ar gases, when administered with alternating cycles of bottled air, produced a nontoxic, hypoxic immobilisation from which aphids recovered fairly rapidly to walk and probe, apparently normally.