The effects of four powdery mildew fungicides on the safety coefficient and predation behavior of Neoseiulus californicus(McGregor)(Acari:Phytoseiidae)
[Aim]To determine the effects of four powdery mildew fungicides,ethirimol,tebuconazole,myclobutanil and pyraclostrobine,on the safety coefficient and predation behavior of Neoseiulus californicus(McGregor)(Acari:Phytoseiidae).The findings of this study will establish an experimental foundation for the combined application of fungicides and predatory mites.[Methods]The acute toxicity and safety coefficient of four fungicides on N.californicus were determined using the leaf disk residual toxicity method.The direct predation,functional response,and search rate of N.californicus on Tetranychus urticae Koch was assessed following treatment with ethirimol,tebuconazole,myclobutanil and pyraclostrobine.[Results]The acute toxicities of the four fungicides to N.californicus were all low,with tebuconazole,ethirimol,myclobutanil,and pyraclostrobine,having safety coefficients of＞3 333.333,＞631.578,563.943 and 19.464,respectively.Following treatment with the four fungicides at the maximum recommended field dose,the functional responses of each N.californicus mite preying on T.urticae remained at Holling's Type Ⅱ.There was no effect of ethirimol treatment on the direct predation amount,predation function,or search rate of N.californicus on T urticae.At higher prey densities,tebuconazole treatment resulted in reduced eggs and protonymph predation.Myclobutanil treatment reduced predation of eggs,protonymph mites,and adult mites,whereas pyraclostrobine treatment reduced predation of all mite developmental stages.The predation function of N.californicus was negatively affected by the effects of tebuconazole,myclobutanil and pyraclostrobine,which increased prey handling time and decreased the maximum predatory amount and predation capacity.Tebuconazole treatment reduced predation of T.urticae eggs and protonymphs by 21.21％and 26.80％,respectively.Myclobutanil treatment reduced T.urticae egg,protonymph,and adult predation by 27.89％,40.06％,and 42.60％,respectively.Finally,Pyraclostrobine treatment reduced T urticae egg,larva,protonymph,deutonymph,and adult predation by 30.90％,64.63％,65.26％,40.67％and 48.91％,respectively.Pyraclostrobine treatment was the most effective at reducing N.californicus search rate,followed by myclobutanil and tebuconazole.[Conclusion]Selective use of fungicides to control powdery mildew should be emphasized when using N.californicus to manage T.urticae.Based on the findings of this study we recommend prioritizing the use of ethirimol,while tebuconazole and myclobutanil should be used with caution,and pyraclostrobine should only be used with careful consideration.
Neoseiulus californicus(McGregor)cooperative control of pests and diseasesfacility agriculturepowdery mildewfunctional response
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