Effect of NPV and NPV in combination with insecticides on Spodoptera litura
2002
Tran Thi Kieu Trang | S.Chaudhari
The susceptibility of different stages of Spodoptera litura larvae to NPV was determined by bioassay. The LC50 values were found to increase with the age of host. There was 1,500,000 folds increase in LC50 value from 2-day-old larvae (1x103PIB/ml) to the 8-day-old larvae (1.5x109 PIB/ml). As the insect grows, there is apparent dilution effect, in that more viruses are required to initiate a lethal infection at later larval age. LT50 values increased from 4.4 days for 2 day old larvae to 9.4 days for 8 day old larvae. This suggested that an increase of resistance with age when infected. LT50 apparent to be dose dependent. The estimated LT50 increased with the increase larval age whereas, it decreased with the increase dose. The action of nuclear polyhedrosis virus of Spodoptera litura (Fabricius) in combination with sublethal concentration of thiamethoxam (thianocotinyl), diflubenzuron (chitin synthesis inhibitor) and imidacloprid (chloronicotinyl) was investigated on 5 day old larvae of Spodoptera litura. Nuclear polyhedrosis virus with thiamethoxam at 50ppm produced synergistic effect while at lower and higher 50ppm produced additive effect. In the case of diflubenzuron in combinaton with nuclear polyhedrosis virus the concentration of diflubenzuron was tested from 1-10ppm have synergistic effect while imidacloprid at the higher concentration 10ppm given antagonistic effect
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