Abstract
Cabbage aphid, Brevicoryne brassicae L., and turnip aphid, Lipahis eyrsimi Kalt., are the regular insect pests of Brassica crops in Southern Punjab, Pakistan. Population development of and losses to yield and yield components due to these two aphid species were examined on late sown crops of Brassica napus L., Brassica juncea L., and Brassica carinata A. Braun under sprayed and unsprayed conditions during 2007-08 at Mulatn. Populations of both the species of aphids were statistically similar on three species of Brassica in unsprayed plots. Losses to yield, plant height, numbers of pods per plant, pod length, numbers of seeds per pod and pod weight were statistically similar across all the three species in untreated plots, those of thousand seeds weight was different. B. napus, B. juncea and B. carinata suffered 75.06, 77.25 and 81.86% losses from aphids in yield where insecticides were not applied. Pod weight, pods per plant and yield per ha., was significantly increased by application of insecticides for all the three species. Due to heavy losses in yield and yield components we recommend insecticide application for reducing losses due to aphids.