Biology, management of Earias spp. and estimation of pesticide residue in okra
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Date
2020
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CCSHAU, Hisar
Abstract
Investigations was carried out on biology and morphometric of okra shoot and fruit borer, Earias insulana on okra, efficacy and residue of noval insecticides in okra crop during Kharif, 2019 at CCS HAU, Hisar. Studies on biology and biometrics of E. insulana revealed that the average number of eggs laid by a female were 49.8 ± 9.58. The freshly laid eggs were bluish green in colour and small globular in shape with mean diameter of 0.5 ± 0.02 mm. Average duration of incubation and oviposition period was 4.1 ± 0.99 and 5.7 ± 0.95 days, respectively. The first, second, third and fourth instar larvae measured on an average 1.61 ± 0.20, 3.65 ± 0.29, 6.99 ± 0.67 and 11.21 ± 1.08 mm in length and 0.75 ± 0.35, 1.78 ± 0.18, 2.21 ± 0.17 and 2.75 ± 0.24 mm in breadth, respectively. Duration of larval and pre-pupal period was 13.8 ± 0.79 and 0.8 ± 0.28 days, respectively. The pupae were brown coloured stout and measured on an average 9.56 ± 0.37 mm and 2.64 ± 0.11 mm in length and breadth with duration of 8.5 ± 0.85 days. Longevity of adult male moth varied from 8 to 10 days and 10 to 11 days for females. Total life period of male and female ranged from 33.5 – 38.5 and 35.5 – 40 days, respectively. Adult male moth was having an average length and breadth (with expanded wings) of male 9.57 ± 0.49 mm and 20.9 ± 0.88 mm, whereas, the female measured on an average 10.08 ± 0.57 mm in length and 21.7 ± 1.06 mm in breadth (with expanded wings). Sex ratio in E. insulana was recorded as 1:0.72 (male: female). Results of efficacy of noval insecticides against Earias spp. in okra showed that larval population remained active in field from 32nd to 42nd SMW and reached to maximum (8.67 larvae/ 5 plant) during 39th SMW. Correlation studies of larval population exhibits a significant negative correlation with maximum temperature, minimum temperature, average temperature, evening relative humidity and total rainfall. Per cent shoot and fruit infestation were also significantly negative correlated with maximum temperature, minimum temperature and average temperature. Results on bio-efficacy revealed that chlorantraniliprole 18.5% SC showed significantly lower larval population, shoot infestation (%) and fruit infestation (%) per plant as compared to other treatments, while B. bassiana 1x10-9cfu found least effective for controlling Earias spp. The fruit yield (8.61 t/ha) was also significantly higher in chlorantraniliprole 18.5% SC when compared to the remaining treatments. Dissipation of chlorantraniliprole in okra fruits followed first order kinetics with half-life period of 2.04 and 2.06 days at single (30 g.a.i./ ha) and double doses (60 g.a.i./ ha) respectively. Chlorantraniliprole applied at 50% fruiting stage, residues reached to LOQ (Limit of Quantification) of 0.01 after 7th and 10th day at single (T1) and double doses (T2) respectively with no residue in soil collected at time of harvest in both doses.