Vol. 10, Issue 10 (2021)

Author(s):
Khyali Ram, Dalip Kumar, Deepika Kalkal and Puneet

Abstract:
The field study was conducted at CCS HAU, Cotton Research Station, Sirsa during Kharif 2019 to study the seasonal abundance of sucking pests in Bt cotton and to assess the impact of abiotic (weather variables) and biotic factors (natural enemies) on their population build-up. The population abundance of sucking pests viz., leafhopper, Amrasca biguttula biguttula (Ishida); thrips, Thrips tabaci Lindemann and whitefly, Bemisia tabaci (Gennadius) was recorded at weekly intervals using the standard methods of observation. Beat-basket method of observation was followed for recording the population of natural enemies viz., green lace wing, Chrysoperla zastrowi sillemi; lady bird beetle, Coccinella septempunctata; spiders and yellow wasps, Vespa spp. The number of sucking pests was found fluctuating during course of study and their active period was observed during 25^th to 42^nd SMW however the population of thrips was disappeared after 36^th SMW. Leafhoppers and whitefly were found in significant positive correlation with relative humidity while significantly positive association of thrips was observed with rainfall. Natural enemies were found active during entire study period. They were negatively correlated with population build-up of thrips; meanwhile positive correlation was found with leafhopper and whiteflies; however negative correlation of green lace wings was recorded with whiteflies’ population. Green lace wings were observed at peak during 30^th and 40^th SMW whereas maximum abundance of lady bird beetle was recorded in 30^th and 42^nd SMW. The population of natural enemies was negatively correlated with temperature while green lace wings and lady bird beetle was positively correlated with morning relative humidity and rainfall. Activity of spiders and yellow wasps was highest during 39^th SMW and their negative correlation was observed with rainfall though the positive correlation was established with morning relative humidity.