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ThesisItem Open Access Bioecology and management of whitefly, Bemisia tabaci Gennadius on cotton(CCSHAU, 2014) Chandappa Kedar, Santoshkumar; Saini, R.K.Studies on bioecology and management of whitefly, Bemisia tabaci Gennadius on cotton were carried out during 2011-13, both in the laboratory as well as Research Farm of the Department of Entomology, CCS HAU, Hisar. Biology of the pest was studied under screen house conditions (31.3 to 35.1oC temperature; 43 to 75.8 % R.H.) during July, 2012-13 on potted plants of cotton variety H-1117 and Bt cotton hybrid RCH 134 BG II. The results indicated that Bemisia tabaci female laid on an average 41.2 (34-49) eggs on H-1117 while 59.25 (45-69) eggs on Bt hybrid RCH 134 BG II. The incubation period of the eggs lasted for 2-5 days. Duration of different nymphal instars on H-1117 was 3.0-5.5, 2.5- 4.5, 2.0-5.0 and 3.0-6.0 days for the first, second, third and pupae, respectively. On RCH 134 BG II, the duration was 3.0-5.0, 2.0-5.0, 2.0-5.0 and 4.0-6.5 days for first, second, third and pupae, respectively. Total life span on H-1117 was 21.5-28.0 and 19.0-26.5 days for female and male, respectively, while it was 20.0-27.0 and 18.0-24.5 days for female and male, respectively on RCH 134 BG II. Population dynamics study of B. tabaci nymphs and adults on H-1117 and Bt hybrid RCH 134 BG II indicated that the pest reached its peak twice in the cotton growing season during 2011 and 2012 (28th to 30th SW and 40th to 41st SW). However, in 2013 only single peak of the pest activity was observed (30th SW). Among the abiotic factors, minimum temperature and wind speed had significant negative correlation with adult whitefly population whereas no significant correlation was found with maximum temperature, relative humidity, sunshine and rainfall. Nymphal population had non-significant correlation with all the weather parameters, except evening relative humidity during 2013 where it had a significant positive correlation. Multiple regression analysis between B. tabaci (nymph and adult) and weather parameters revealed that all the weather parameters accounted for 47 to 52 per cent and 34 to 57 per cent variability in adult whitefly population. B. tabaci was recorded on one or the other host plants round the year and as many as 114 host plants belonging to 32 families. On the basis of number of plant species attacked, the families Fabaceae, Asteraceae and Solanaceae were the most preferred families. The highest population density of the pest was recorded on Gossypium hirsutum (35.2 adults/leaf), followed by Solanum melongena (28.3), Lablab purpureus (26.3), Glycine max (25.4) and Vigna umbellata (24.2). A total of 25 species of arthropod natural enemies were found to be associated with B. tabaci in cotton ecosystem during the study period. These included 17 spider species, five coccinellids, one neuropteran, one hemipteran and one parasitoid species. Seasonal abundance of spiders, coccinellids, chrysopids and parasitization on cotton indicated that the peak activity of these predators and parasitoid coincided with peak pest population. Among the abiotic factors, maximum and minimum temperature, and wind speed had significant negative effect on population buildup of spiders, coccinellids and chrysopids. The morning relative humidity showed significant positive correlation with population buildup of spiders, coccinellids, and chrysopids. The weather parameters had no significant effect on the per cent parasitization of B. tabaci nymphs by Encarsia lutea. Predatory potential study of Serangium parcesetosum indicated that during the larval duration of 12.8 days, a larva consumed 560.2 nymphs of B. tabaci. Heavy natural infection of B. tabaci adults by entomopathogenic fungus, Paecilomyces javanicus, was recorded for the first time from north India. Among the various insecticides evaluated, novaluron and azadirachtin were effective against B. tabaci nymphs, while triazophos, acephate, dimethoate, imidacloprid and cartap hydrochloride against adults.