Biology and management of Bihar hairy caterpillar, Spilosoma obliqua Walker on cowpea, Vigna unguiculata (Linnaeus) Walpers and its population dynamics on various pulse crops
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Date
2015
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AAU, Anand
Abstract
Present investigations were carried out on biology and management of Bihar hairy caterpillar, Spilosoma obliqua walker on cowpea and its population dynamics on various pulse crops at Anand Agricultural University, Anand during the year 2013-14. The female laid eggs in masses on lower surface of the upper as well as middle leaves of cowpea. The eggs were greenish in colour and look like seed of grape with flattened base and measured on an average 0.34 ± 0.04 mm in diameter. The mean incubation period was 3.68 ± 0.63 days with the hatching per cent ranged from 78 to 92. Newly hatched larvae feed gregariously on lower surface of leaves by scraping its surface which resulted into papery leaves. Larvae of third, fourth, fifth instars fed the whole leaves except veins and veinlets. Larva passed through six instars. The freshly hatched first instar larva was creamy whitish with shining brown head and having brown spots over entire body from which white hair arises which later turn black and transparent abdominal segment. Distinct three pairs of prologs were clearly observed. The larva in second instar slightly increased in size having light yellow colour body with brown markings on thoracic and last abdominal segment. Third instar larva was similar to second instar but the colouration of head and body segments were little darker compared to the second instar. The fourth instar larva was uniformly yellowish in colour as the segments were brown and tuft of brownish white hairs arose from reddish brown verrucae and the head turned dark brownish black. The fifth instar larva was dark yellow with reddish tinge in colour and the heads and thoracic shields were dark brown in colour while the legs were reddish brown. The full-grown sixth instar larva had dark black head with brownish legs and uniformly reddish brown body with brownish black verrucae on which there were whitish hairs. The average duration of first to sixth instar larvae was 3.12 ± 0.78, 3.44 ± 0.51, 3.56 ± 0.51, 2.56 ± 0.51, 3.72 ± 0.46 and 2.72 + 0.46 days, respectively. The lengths of first to sixth instar larvae were 4.54 ± 0.82, 7.56 ± 1.11, 9.90 ± 0.40, 18.34 + 0.80, 22.08 ± 1.91 and 26.29 +1.14 mm, respectively whereas its breaths were 0.79 ± 0.22, 1.59 ± 0.11, 2.01 ± 0.16, 2.36 + 0.28, 3.30 ± 0.56 and 5.10 + 0.56 mm. The widths of the head capsule of respective instars were 0.61 ± 0.11, 1.09 + 0.25, 1.68 + 0.19, 2.06 ± 0.14, 2.84 + 0.13 and 3.71 ± 0.41 mm, respectively. The prepupal period ranged from 2 to 3 days with an average of 2.60± 0.50 days. The average lengths and widths of the pre-pupae were 24.71 + 1.58 and 4.06 + 0.32 mm, respectively. The newly formed pupae were soft and green or pale brown in colour. The average pupal period of male and female were 9.04 + 0.73 and 9.36 + 0.49 days, respectively. Average lengths and breadths of male and female pupae were 21.02 + 1.90 and 5.54 + 0.43 mm and 22.19 + 0.84 and 5.73 + 0.48 mm, respectively. The adult moths were straw in colour with orange and brown streaks over the forewings, white streaks along the anterior margin and black spots on each abdominal segment. Average longevity of male and female moths were recorded to be 5.00 + 0.82 and 7.08 + 0.81 days, respectively. The average pre-oviposition, ovipostion and post ovipositon periods were 2.40 + 0.50, 5.16 + 0.85 and 2.84 + 0.75 days, respectively with, average fecundity of 976.84 + 194.58 eggs per female. Study on seasonal abundance of S. obliqua on various pulse crops revealed that the pest was active on various crops from 3rd week of July to 4th week of October. The higher activity on cowpea, green greim, black gram and soybean was found during pt week of August to 2nd week of October. The pest showed significantly positive correlation with bright sunshine hours and maximum temperature and while significantly negative correlation with evening relative humidity. The study on bio-efficacy of different insecticides in laboratory revealed that significantly maximum larval mortality (81.70 %) was found in treatment thiodicarb 75 WP. Chlorphyriphos 20 EC and fenvalerate 0.4 % DP were found to be next best insecticides. These insecticides also showed same type of effectiveness in the field experiment. Lowest leaf damage and highest yields were also recorded in the treatment of thiodicarb 75 WP which was followed by fenvalerate 0.4 % DP, chlorphyriphos 20 EC, methomyl 40 SP, novaluron 10 EC, quinalphos 25 EC and emamectin benzoate 5 SG, respectively. The data on economics showed that maximum NICER was obtained in the treatment of chlorpyriphos 20 EC which was followed by fenvalerate 0.4 % DP, thiodicarb 75 WP, quinalphos 25 EC, methomyl 40 SP and novaluron 10 EC.
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AGRICULTURAL ENTOMOLOGY, AGRICULTURE, MANAGEMENT