Laboratory efficacy of selected insecticides against onion armyworm, Spodoptera exigua (Hubner) (Lepidoptera:Noctuidae)
2018
Navasero, M.V. | Ardez, K.P. | Bato, M.B.
Nineteen formulated insecticide products were evaluated for their efficacy against third instar larvae of onion armyworm (OAW), Spodoptera exigua (Hubner), using the leaf-dip bioassay method. Dose-mortality response curves were generated using Polo Plus and Logit Analysis version 2.0. Lethal dose estimates were calculated using PriProbit ver. 1.63. Effective dose-recommended rateration (ED-RR ratio) was used for comparison of their relative efficacy. Complete dose-related mortality data were generated for 10 of these products, namely: Bacillus thuringiensis Berliner, beta-cypermethrin chorantraniliprole, chlorfenapyr, indoxacard, spinetoram, spinosad, methomyl, pyridalyl, and a mineral oil. There of these products (spinetoram chlorfenapyr . spinosad) were found efficacious to 3rd instar larvae based on their ED-RR ratios while the mineral oil had high ovicidal activity. Dose-mortality response curves at different periods of exposure were not significant for chlorfenapyr indicating that it is fast acting. In contrast, dose-mortality response corves for the other compounds were significant, indicating these are relatively slow acting with the exceptions of beta-cypermethrin and methomyl. The last two are known to have quick knockdown effects but significant differences in dose-mortality curves suggest rather high level of resistance in OAW. Results of laboratory assay for the rest of the compounds showed very low, if not total lack of, efficacy against OAW. Considering the highest doses already tested for these compounds, except for pyrdalyl, their ED-RR ratios were very high but the recorded mortalities did not go beyond 70%.
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