Impact of temperature and soybean genotypes on biology of tobacco caterpillar and its mortality assessment with chitin synthesis inhibitors under in vitro condition

Abstract

Laboratory experiment was conducted to assess the influence of temperature regimes (20, 25 and 30 °C) on biology of tobacco caterpillar in soybean genotypes and its mortality assessment with chitin synthesis inhibitors at bio control lab, Jabalpur. Soybean genotypes include JS-335, JS 97-52, JS22-09 and JS20-116. Among genotypes JS-335 recorded higher number of eggs (1652.11 eggs/female) and hatchability percentage (88.04), while it were lower on JS JS97-52 as 257.33 eggs/female and 63.65% respectively. Longest incubation period was observed on JS97-52 (6.22 days) and significantly shortest on JS-335 (3.89 days). The mean incubation period significantly decreased with increase in temperature. However, longest incubation period was recorded at 20±2 °C (6.67) days and it was shortest at 30±2 °C (3.92 days), respectively. Among genotypes total larval duration was observed to be shortest on JS-335 (15.89 days). longest on JS97-52 (24.89 days). Among temperature regimes, it significantly decreased with increase in temperature, being 27.58, 20.08 and 14.92 days which were observed at 20±2 °C, 25±2 °C and 30±2 °C, respectively. The total larval survival significantly increased with increase in temperature, being 61.67, 63.33 and 79.17% at 20±2 °C, 25±2 °C and 30±2 °C, respectively. Highest pupation percentage and adult emergence was recorded on JS-335 genotype. The S. litura 2nd instar larval mortality marginally increased with increase in concentration coupled with elapse of time in all the treatments. It indicated that mortality was clearly dose and time dependent. Lufenuron at higher concentration (100 ppm) was found to be highly effective as it recorded maximum larval mortality at 3 days after treatment (DAT) followed by Novaluron and Diflubenzuron @ 200 and 300 ppm, respectively.