Incidence and abundance of thrips, Thrips spp. on varieties of brassica

The present studies on the incidence and abundance of thrips, Trips spp. on different varieties of brassica were carried out under field condition. Three varieties viz., Toria selection, S-9, Canola were sown in a randomized block design. There were 10 rows of each variety. The distance between row to row was 16". The observation was taken in the morning time, selecting 10 plants at random and five leaves/plant from each variety. The observations on thrips were recorded twice a week starting from 3rd week of November to 1st week of March. The results on mean per plant population of thrips on different brassica varieties showed that the incidence of pest was invariably recorded during the entire period of study in all varieties. The thrips population increased gradually with the plant phenology and reached to its peak during 3rd week of January (54.10 thrips/plant) on canola variety. Whereas, on toria selection (24.0 thrips/ plant) and S-9 (23.5 thrips/plant) during 4th week of January. Amongst these varieties the highest (21.93 thrips/plant). Population was recorded on Canola variety and found susceptible to thrips, whereas Toria selection (6.65 thrips/plant) and S-9 (6.21 thrips/plant) were found moderately, susceptible to the attack of brassica thrips. No application of insecticide was applied in and around the experimental field. Thrips infestation was invariable with the brassica plant phonology. Thrips population was recorded during 3rd week November on all brassica varieties. Maximum population of thrips was recorded during 3rd week of January in Canola variety only, whereas, maximum population of thrips on Toria Selection and S-9 was recorded during 4th week of January. Canola variety harboured significantly the highest thrips population and was found susceptible variety to thrips attack. Toria Selection and S-9 varieties were found moderately susceptible to thrips attack. It is not fair to make recommendations on the basis of one-year studies, however it could be suggested that susceptible variety should be discarded from breeding programme. Further studies on resistant mechanisms are also suggested.