Observations on host preferences and epidemiology of aphid species associated with legume crops.
In the spring and summer of 1979-80, bait plants of pea, dwarf bean (Phaseolus vulgaris), broad bean (Vicia faba) and subterranean clover (Trifolium subterraneum) were set out and replaced weekly in the middle of a lucerne crop, a clover crop and a pea crop in New Zealand; 13 species of aphids were collected from the bait plants. Myzus persicae (Sulz.), Acyrthosiphon kondoi Shinji, Aulacorthum solani (Kalt.), Aphis craccivora Koch, Acyrthosiphon pisum (Harris) and Macrosiphum euphorbiae (Thos.), in decreasing order of frequency, were considered to be legume aphids. Myzus persicae was found most frequently on dwarf bean and pea, and A. kondoi on dwarf bean and clover. Aulacorthum solani occurred at a similar frequency on all bait plants except clover, where very few were found. Acyrthosiphon pisum preferred broad beans to clover and peas, and was least frequent on dwarf beans. Macrosiphum euphorbiae was found in low numbers on all bait plants except clover, on which none was found. The weekly records also showed that the peak flying time of A. pisum, Aphis craccivora and M. euphorbiae was later than for the other 3 species. High numbers of late-instar apterae of Aulacorthum solani on bait plants showed that the apterae of this species were extremely mobile. Weekly records of aphid populations on clover and lucerne surrounding the bait plants showed that white clover was the main overwintering host for A. solani and that lucerne was the overwintering host for Acyrthosiphon kondoi. Early spring populations of A. pisum were at low levels on both lucerne and white clover.