Abstract
The joint use of baculoviruses and synthetic insecticides for integrated pest management requires the study of the additive, synergistic or antagonistic effects among them on pest mortality. Droplet bioassays were conducted with Autographa californica multiple nucleopolyhedrovirus (AcMNPV), Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) and seven insecticides (azadirachtin, Bacillus thuringiensis, cyantraniliprole, emamectin, metaflumizone, methoxyfenozide and spinetoram) on Spodoptera exigua and Spodoptera littoralis. The lethal concentrations LC50 and LC95 were calculated through probit regressions. Then, the sequential feeding of insecticides and nucleopolyhedroviruses was studied. Larvae were provided with the LC50 of one insecticide, followed by the LC50 of one nucleopolyhedrovirus 24 h later. The inverse order was also conducted. The insecticide LC50 and LC95 were higher for S. littoralis than for S. exigua. AcMNPV showed greater toxicity on S. exigua than SpliNPV on S. littoralis. Emamectin showed synergy with AcMNPV when the chemical was applied first, and metaflumizone and AcMNPV were synergistic regardless of the order of application, both from the first day of evaluation. SpliNPV was synergistic with azadirachtin and emamectin when it was applied first, but synergy was reached after 12–13 days. Excellent control is possible with the LC50 of azadirachtin, emamectin and metaflumizone in combination with nucleopolyhedroviruses, and merits further study as a means of controlling lepidopteran pests.
Highlights
The increasing use of synthetic organic chemicals has resulted in resistance and ecological concerns associated with environmental contamination and toxicity to non-target organisms [1]
The LC95 of four insecticides and the LC50 of metaflumizone exceeded the maximum field concentrations according to national recommendations under our experimental conditions (Tables 1 and 2)
The LC50 and LC95 of azadirachtin, B. thuringiensis, cyantraniliprole, methoxyfenozide and spinetoram were higher for S. littoralis than for S. exigua (Tables 2 and 3)
Summary
The increasing use of synthetic organic chemicals has resulted in resistance and ecological concerns associated with environmental contamination and toxicity to non-target organisms [1]. Baculoviruses are double-stranded DNA viruses that control different orders of insects, including the larval stages of many lepidopteran pests of food crops. The family Baculoviridae comprises four genera, of which viruses of the Alphabaculovirus genus (lepidopteran nucleopolyhedroviruses, NPV) have shown considerable potential as bioinsecticides [7,8]. They are host-specific and have no adverse effects on natural enemies or other non-target insect populations, whereas the application of conventional insecticides reduces the abundance of beneficial agents [9,10]
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