Relative feeding rates of Brevicoryne brassicae and Myzus persicae on Brussels sprout plants in relation to their susceptibility to systemic insecticides

SUMMARY Brevicoryne brassicae and Myzus persicae removed similar quantities of 32P‐labelled material from Brussels sprout leaves whether they fed for 24 or 48 h periods. They also removed similar quantities from untreated leaf disks as from leaf disks treated with a sub‐lethal dose of menazon. When a lethal dose was used, the uptake of 32P by B. brassicae was significantly less than by M. persicae. M. persicae excreted a greater proportion of 32P label in the honeydew than B. brassicae and a greater proportion of the amount absorbed was lost in the progeny of this aphid than in B. brassicae. B. brassicae was 6.2 times more susceptible than M. persicae to dimethoate acting systemically. When it was applied topically the aphids were equally susceptible. Considerable variation in uptake of 32P occurred between replicates and the factors that could influence this are discussed.