Studies on the population dynamics, monitoring, mortality and control of Bemisia tabaci (Genn.) on cotton crop
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Date
2020-07
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CCSHAU, Hisar
Abstract
The present investigation entitled “Studies on the population dynamics, monitoring, mortality and
control of Bemisia tabaci (Genn.) on cotton crop” was carried out during 2017 and 2019, both in the Laboratory
as well as at Experimental Area, Department of Entomology, CCS Haryana Agricultural University, Hisar. The
population dynamics study revealed that peak activity of whitefly and its parasitoids, Encarsia spp. was
observed from April to May on brinjal, cucumber and okra; in August on greengram, soybean and okra; and in
September on cotton. In descending order, the peak abundance of whitefly was observed on cotton followed by
cucumber, soybean, greengram, brinjal and okra while, parasitization by Encarsia spp. was highest on soybean
followed by cotton, greengram, brinjal, cucumber and okra during 2017 and 2019. A total of 46 host plants
belonging to 12 families were reported to be infested by whitefly, B. tabaci. Monitoring studies revealed that
peak population of whitefly adults on yellow sticky traps (14,392 whitefly adults/trap) and in direct count (19.06
whitefly adults/leaf) was recorded during 38th SMW i.e., 3rd week of September; whereas, whitefly nymphal
population i.e., 31.2 per leaf by direct count method was at its peak during 39th SMW i.e., 4th week of
September. In direct count, whitefly adult population showed a significant negative correlation with evening
relative humidity (r = -0.53) (r = -0.56) and total rainfall (r = -0.61) (r = -0.58) during 2017 and 2019,
respectively. Nymphal population showed significant negative correlation with evening relative humidity (r = -
0.52) and total rainfall (r =-0.54) in 2019. Population captured on yellow sticky traps showed no correlation with
weather parameters in 2017. While, whitefly adults captured on both horizontal (r = 0.54) (r = -0.51) and
vertical traps (r = 0.55) (r = -0.51) showed significant positive and negative correlation with sunshine hours and
total rainfall, respectively in 2019. Across all the immature developmental stages, principal mortality governing
factor was dislodgement in cotton, predation in brinjal and parasitism in cucumber crop. The highest mortality
occurred during fourth nymphal instar on cotton, brinjal and cucumber. Azadirachtin 0.03 per cent @ 7.5 ml/l
was found more effective against whitefly adults and nymphs. However, it remained significantly at par with
Azadirachtin 0.03 per cent @ 5 ml/l (recommended dose) and Azadirachtin 0.15 per cent at the dose of 7.5 ml/l
and 5 ml/l.