Effect of conventional and neonicotinoid insecticides against aphids on canola,Brassica napus L. at Multan and Dera Ghazi Khan

Conventional (bifenthrin,carbosulfan and methamidophos) and neonicotinoid insecticides (thiamethoxam and imidacloprid) were sprayed once to test their toxicity to cabbage aphid,brevicoryne brassicae l. and turnip aphid,lipaphis erysimi (kalt.) on canola. insecticides were applied on 14th march,2005 at multan. after seven days of application all the insecticides proved to be similarly toxic to aphids but statistically higher numbers of both aphid species were observed in untreated plots. in another experiment split plot design was employed and four b. napus varieties,con-i,con-ii,ks-75 and abaseen were planted in sub-plots keeping insecticides (thiamethoxam,imidacloprid and carbosulfan) in main plots at dera ghazi khan. insecticides were applied on 2nd and 12th march,2006. the interaction between varieties and insecticides at the dera ghazi khan trial was non-significant when analyzed in split plot design. therefore,population data of b. brassicae and l. erysimi were pooled for varieties. densities of both the species were statistically lower after nine days of application in plots where insecticides were applied when compared to untreated plots. however,aphid numbers were too high even after three days of application particularly after first spray. results of this study suggest that insecticides should not be applied at pod-filling stage (first week of march) to manage aphids on canola. copyright 2010 zoological society of pakistan.