BIOLOGY, SEASONAL INCIDENCE AND MANAGEMENT OF RED SPIDER MITE, Tetranychm urticae KOCH IN OKRA 1998
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Date
2015-06
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JAU, JUNAGADH
Abstract
An investigations were carried out on biology and management of okra red spider mite, T. urticae at Junagadh Agricultural University, Junagadh, Gujarat during
2013-14.
Studies on biology of red spider mite, T urticae revealed that both the sexes passed through five stages viz., egg, larva, protonymph, deutonymph and adult with a short resting period known as quiescent. The eggs were laid singly, mostly on the lower surface of leaves. The eggs were smooth, soft, round and translucent white. The incubation period was 3.37 ± 1.07 days with 91.06 ± 3.84 per cent eggs hatching. The average larval, nymphochrysalis, protonymphal, deutochrysalis and deutonymphal periods were 1.78 ± 0.58 and 2.67 ± 0.66, 0.65 ± 0.36 and 0.70 ± 0.34, 2.44 ± 0.57 and 2.83 ± 0.75, 0.74 ± 0.42 and 0.96 ± 0.42, 2.20 ± 0.77 and 2.70 ± 0.88 days for male and female, respectively. The matured deutonymph remained in quiescent stage (teliochrysalis) for 0.80 ± 0.27 days in female. This stage was only found in female T. ^rticae whereas in case of male it was absent. The total developmental period was longer in female (10.66 ± 1.28 days) as compared to male (7.81 ± 1.40 days). The average pre oviposition, oviposition and post oviposition periods were 3.00 ± 1.56 and 1.80 ± 1.13 5-55 ±1.61 and 8.37 ± 1,22, 2.30 ± 1.08 and 3.23 ± 1.04 days in unmated and mated females, respectively. The fecundity for unmated and mated female was 26.15 ± 7 74 and 78.37 ± 13.26 eggs. The male lived shorter (10.10 ± 1.65 days) than the mated (13.40 ± 1.92 days) and unmated (10.85 ± 2.54 days) females. The total life period occupied by T. i^rticae 17.91 ± 2.55 days in male and 24.06 ±2.14 days in female.
Seasonal incidence of T. urticae revealed that the mite population observed from 2"'' week of July to throughout crop life. The higher mite population was noticed during 2"'' week of August to 2"*' week of October with peak during month of September, 2013 and October, 2014. The mite activity was declined when last picking was completed. Predatory mites and predatory beetle activity were started from 4"' and 5"^ week of July. Wind speed had highly significant negative correlation while, minimum temperature, moming, evening and mean relative humidity and vapour pressure had negative correlation with mite population during kharif 2013-14.