Spatial distribution and effect of leaf characters on development of whitefly, Bemisia tabaci (Gennadius) in cotton
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Date
2022-07
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CCS HAU, Hisar
Abstract
The present study on Spatial distribution and effect of leaf characters on development of whitefly, Bemisia tabaci (Gennadius) in cotton was conducted at Chaudhary Charan Singh Haryana Agricultural University, Hisar. The findings of investigation revealed that among three cotton cultivars the middle leaves of Bt cotton had the highest number of whitefly nymph (36.08 nymphs/leaf) in comparison to American (34.64 nymphs/leaf), and Desi cotton (32.10 nymphs/leaf). The population of whitefly nymphs was highest on the middle strata leaves in each cultivar, followed by the upper strata leaves, and it was minimum on the lower strata leaves. The maximum population of adults was observed on upper leaves of Bt cotton (4.26 adults/leaf) followed by American (3.09 adults/leaf) and minimum was on Desi cotton (2.63 adults/leaf). The maximum population of whitefly adult was observed on upper strata leaves than on middle strata leaves while minimum on lower strata leaves in each cultivar. There were two peaks of B. tabaci adults, observed in 34th and 40th SMW (i.e., 3rd week of August and 1st week of October). Likewise, two peaks of nymphal population were observed in 35th SMW 41st SMW (4th week of August and 2nd week of October) with number 33.04, 30.69, 27.41 and 25.98, 23.88, 20.07 nymphs/leaf in Bt, American and Desi cotton, respectively . Whitefly adult population had significant positive correlation with morning relative humidity and minimum temperature in Desi cotton only. Relative morning humidity showed a significant positive correlation with nymphal population in all the three cultivars. Several species of arthropod natural enemies were found and these included spider species, coccinellids, Chrysoperla spp. and parasitoids species. The peak activity of different natural enemies was observed during early October (40th to 43rd SMW). The study revealed that on both i.e., 45 days and 90 days plant, the whitefly development was high on 25 days old leaf on all three cultivars. Leaf area, thickness and trichome density showed a positive and significant correlation with 25 days old leaf in all three cultivars. Total chlorophyll in 5 days old leaf had a positive and highly significant correlation with nymphal duration in Desi cotton only. Tannin content showed a positive and significant correlation with egg hatchability on 25 days old leaf in Bt cotton.