Acaricidal activity of commercialized insecticides against Haemaphysalis longicornis (Acari: Ixodidae) nymphs

•The acaricial activity of 13 commercialized insecticides in Korea against Haemaphysalis longicornis nymphs was evaluated.•The activity of insecticides belonging to pyrethroids was high.•Especially, deltamethrin 1.5% and lambda-cyhalothrin 5.5% exhibited 93 and 87% mortality at 7 days after treatment.•However, their residual acaricidal activity was rapidly decreased under field conditions.

The acaricial activity of 13 commercialized insecticides in Korea against the hard tick nymphs Haemaphysalis longicornis collected in a field was tested using nymph dipping and folded filter paper methods and a spraying-residual assay. In a nymph dipping bioassay, 100% mortality at all tested doses was observed in insecticides containing active ingredients such as phthalthrin 8% + d-phenothrin 2% + piperonyl butoxide 20%, deltamethrin 1.5%, pyrethrum 0.5%, lambda-cyhalothrin 5.5%, alpha-cypermethrin 10% and teflubenzuron 50%, whereas the insecticide containing etofenprox 5% + octachlorodipropyl ether 11% at recommended dose (RD) and 0.5 times RD showed 97 and 90% activity, respectively. Other insecticides containing alpha-cypermethrin 5%, polyoxyethylene isostearylether 10%, etofenprox 5%, bistrifluron 10% and Bti did not show any significant activity. In the folded filter paper contact test with nymph H. longicornis at RD, polyoxyethylene isostearylether 10%, deltamethrin 1.5% and alpha-cypermethrin 10% showed 100% mortality at 1 day after treatment (DAT). At 7 DAT, polyoxyethylene isostearylether 10%, deltamethrin 1.5% and lambda-cyhalothrin 5.5% exhibited 100, 93 and 87% mortality. Although the selected 5 insecticides showed strong mortality under laboratory conditions, their residual effect sprayed on field grown lawn leaves significantly decreased depending on DAT. Etofenprox 5% mixture (+ octachlorodipropyl ether 11%) only showed 93 and 80% mortality at 1 and 2 DAT, respectively. Polyoxyethylene isostearylether 10% gave 0% mortality at even 1 DAT and the other insecticides also showed 60–70% mortality at 1 DAT. These results indicate that pyrethroid insecticides gave good activity against the H. longicornis nymphs but their residual effect is within 1 DAT under field conditions.

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