TY - JOUR

T1 - Implications of sequence and timing of exposure for synergy between the pyrethroid insecticide alpha-cypermethrin and the entomopathogenic fungus Beauveria bassiana

AU - Meyling, Nicolai Vitt

AU - Arthur, Samuel

AU - Pedersen, Kathrine Eggers

AU - Dhakal, Suraj

AU - Cedergreen, Nina

AU - Fredensborg, Brian Lund

PY - 2018

Y1 - 2018

N2 - 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.

AB - 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.

KW - Animals

KW - Beauveria/physiology

KW - Insect Control/methods

KW - Insecticides/pharmacology

KW - Larva/drug effects

KW - Pest Control, Biological

KW - Pyrethrins/pharmacology

KW - Tenebrio/drug effects

KW - integrated pest management

KW - insect immune response

KW - combination effects

KW - independent action modelling

KW - Tenebrio molitor

U2 - 10.1002/ps.4926

DO - 10.1002/ps.4926

M3 - Journal article

C2 - 29603560

VL - 74

SP - 2488

EP - 2495

JO - Pest Management Science

JF - Pest Management Science

SN - 1526-498X

IS - 11

ER -