Lethal and Sublethal effects of Novaluron and Spinosad on developmental biology of potato tuber moth, Phthorimaea operculella (Zeller)

Abstract

Abstract Phthorimaea operculella (Zeller) is one of the most serious pests of potatoes. This study was conducted to evaluate the effects of novaluron and spinosad on different life stages, developmental period and persistence of these insecticides in storage against P. operculella. The bioassay studies revealed the LC50 values of novaluron and spinosad against eggs were calculated to be 0.003 and 0.004 per cent, respectively. Against larvae, the LC50 values of novaluron for I-IV instar larvae of P. operculella were calculated to be 0.001, 0.003, 0.009 and 0.01 percent, respectively. In case of spinosad, the LC50 values for I-IV instar larvae were determined to be 0.0003, 0.0006, 0.001 and 0.002 per cent, respectively. Both novaluron and spinosad also revealed sublethal effects when one-day old eggs were treated. Maximum incubation period of 5.43 days and total larval period was observed with novaluron (0.0003%), compared to 4.20 days in control. The adult longevity was significantly affected, and the male and female longevity in novaluron treatment ranged 4.73 and 4.64 days. In control, the male and female longevity has been found to range from 6.2 and 5.56 days, respectively. The fecundity range was also significantly affected when treated with these two compounds. In storage experiment, minimum tuber damage (2.63%) was recorded in spinosad (0.01%), and novaluron (0.007%) registered 54.39 per cent tuber infestation, after 30 days of exposure.