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Implications of sequence and timing of exposure for synergy between the pyrethroid insecticide alpha‐cypermethrin and the entomopathogenic fungus Beauveria bassiana
Author(s) -
Meyling Nicolai V,
Arthur Samuel,
Pedersen Kathrine E,
Dhakal Suraj,
Cedergreen Nina,
Fredensborg Brian L
Publication year - 2018
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.4926
Subject(s) - beauveria bassiana , bassiana , entomopathogenic fungus , pyrethroid , biology , pest analysis , toxicology , cypermethrin , pesticide , biological pest control , botany , agronomy
BACKGROUND Combining low doses of chemical insecticides with entomopathogens constitutes a sustainable pest control method, but the significance of the timing and sequence of exposures needs clarification. We studied lethal effects of combinations of the entomopathogenic fungus Beauveria bassiana (KVL03‐122) and the pyrethroid alpha‐cypermethrin on the beetle Tenebrio molitor under varying timing and sequence of exposure. Synergy over time was evaluated in relation to the model of independent action (IA). We expected that increased progression of disease caused by B. bassiana would make beetles more susceptible to the insecticide, leading to enhanced synergy. RESULTS Synergistic effects between B. bassiana and alpha‐cypermethrin were observed when B. bassiana was applied first, but only when the interval between applications was >48 h. With 72 h between exposures, mortality had increased to 100% after 8 days, in contrast to the 60% mortality expected. No synergy was observed when the insecticide was applied prior to fungal exposure within 24 h. CONCLUSION The sequence and timing of exposure do matter to achieve synergistic mortality by combining B. bassiana and alpha‐cypermethrin, and the IA model proved to be a strong tool with which to evaluate the interactions of the two stressors over time. Pest control strategies could include B. bassiana followed by low‐dose exposures to alpha‐cypermethrin after 2–3 days. © 2018 Society of Chemical Industry