Sood, Ajay K.Kaundal, Priyanka2019-01-242019-01-242018-07-23http://krishikosh.egranth.ac.in/handle/1/5810092238Studies on „Insect pest complex of onion in Himachal Pradesh‟ were made in ten localities representing two agro-ecological zones of Himachal Pradesh and at CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur. Thirteen species of insects belonging to six orders and nine families, including ten pestiferous and three beneficial insects were recorded from Zone I and II of Himachal Pradesh. The pestiferous insects were Altica sp., Chromatoyia horticola (Goureau), Euconocephalus sp., Gryllus sp., Helicoverpa armigera Hubner, Melolontha furicicauda Ancey, Nezara viridula Linnaeaus, Spodoptera litura Fabricius, Thrips tabaci Lindeman and Trichoplusia orichalacea Fabricius. The beneficial insects namely, Coccinella septempunctata Linneaus, Coccinella transversalis Fabricius and Hippodamia variegata Goeze were associated. In Zone I and II, nine and ten insect species were recorded at different crop growth stages. T. tabaci and C. septempunctata were prevalent in all the ten localities in bulb initiation and bulb development stage. Abundance of T. tabaci was maximum at bulb development stage. In Zone I, diversity and evenness was observed to be maximum at Berthin and Una, respectively. In Zone II, it was observed to be at Palampur. Diversity was maximum during bulb initiation stage and was followed by bulb development. In Zone I, only T. tabaci was found to be eudominant and other eight were subrecedent. Whereas in Zone II, one eudominant (T. tabaci), one recedent (Altica sp.) and eight subrecedent species were recorded. At Palampur, in rabi onion, thrips activity initiated in mid of February with peak population levels of 4.93 and 4.65 thrips/plant occurring in 2nd fortnight of April during 2017 and 2018, respectively. The peak infestation levels of 69.7 and 69.3 per cent corresponded to the peak population. Thrips population was found to be influenced by maximum and minimum temperature positively and significantly. In late kharif onion, thrips activity initiated during the last week of October with peak population of 4.84 thrips/plant occured in mid December and peak of plant infestation (86%) occurring in second fortnight of December. In all the cropping seasons, thrips population was distributed aggregately. For estimation of thrips population the mean number of samples were 16767, 834 and 241 (P=0.1) and 4192, 209 and 60 (P=0.2) for vegetative, bulb initiation and bulb development stage, respectively in rabi onion. For late kharif onion, sample size of 297 and 140 (P=0.1) and 74 and 35 (P=0.2) was required for scape formation and bulb development to maturity stages, respectively. For precise estimation of thrips population in mid-hill regions of the state, 13:00 hours was found to be the appropriate time of sampling thrips in onion.ennullThesis