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Evaluation of the time–concentration–mortality responses of Plutella xylostella larvae to the interaction of Isaria fumosorosea with the insecticides beta‐cypermethrin and Bacillus thuringiensis
Author(s) -
Nian Xiaoge,
He Yurong,
Lu Lihua,
Zhao Rui
Publication year - 2015
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.3784
Subject(s) - plutella , bacillus thuringiensis , bioassay , biology , entomopathogenic fungus , toxicology , cypermethrin , fungus , larva , pest analysis , biological pest control , botany , pesticide , agronomy , ecology , bacteria , genetics , beauveria bassiana
BACKGROUND Entomopathogenic fungi are potential candidates for controlling Plutella xylostella , a cosmopolitan pest of crucifers. In this study, bioassays were conducted to evaluate the interaction between Isaria fumosorosea and sublethal doses of two insecticides, beta‐cypermethrin and Bacillus thuringiensis , against P. xylostella . RESULTS Data of each assay were in good agreement with the time–concentration–mortality model, indicating a strong dependence of the fungus and insecticide interaction on both concentration and post‐exposure time. Using beta‐cypermethrin 58–116 µg mL −1 or B. thuringiensis 222.5–890 µg mL −1 with the fungus significantly enhanced fungal efficacy. The LC 50 values of the fungus declined over a 1–7 day period after exposure, and the LT 50 values decreased with increasing concentration. Based on LC 50 or LC 90 estimates, synergism between the fungus and beta‐cypermethrin resulted in a 2.7–28.3‐fold reduction in LC 50 values and a 12.1–19.6‐fold reduction in LC 90 values, while synergism of the fungus with B. thuringiensis led to a 2.4–385.0‐fold reduction in LC 50 values and a 4.4–151.7‐fold reduction in LC 90 values. CONCLUSION Results show that sublethal doses of B. thuringiensis and beta‐cypermethrin can synergise I. fumosorosea activity on P. xylostella , suggesting that combination of I. fumosorosea with the two insecticides might offer an integrated approach to controlling P. xylostella in practice. © 2014 Society of Chemical Industry