TY - JOUR
T1 - Mechanisms of resistance to three mite growth inhibitors of Tetranychus urticae in hops
AU - Adesanya, A. W.
AU - Morales, M. A.
AU - Walsh, D. B.
AU - Lavine, L. C.
AU - Lavine, M. D.
AU - Zhu, F.
PY - 2017/5/3
Y1 - 2017/5/3
N2 - Mite growth inhibitors (MGIs), such as etoxazole and hexythiazox, are valuable IPM tools for Tetranychus urticae control in hops due to their unique mode of action and selectivity. Hence, it is necessary to standardize bioassay methods to evaluate the efficacy of MGIs, monitor resistance, and identify mechanisms underlying MGI resistance in the field. Here, we developed a three-tiered approach for evaluating ovicidal toxicity of MGIs to T. urticae, which simulated different MGI exposure scenarios in the field. The most effective bioassay method was direct exposure of T. urticae eggs to MGIs. With this method, four field-collected T. urticae populations showed low-to-moderate resistance to MGIs. Cross-resistance among MGIs and from MGIs to bifenazate and bifenthrin was detected. Besides target site insensitivity, enhanced cytochrome P450 and esterase activities also contribute to the MGI resistance in hop yard-collected T. urticae populations. Low-to-moderate MGI resistance in T. urticae populations may be mediated by multiple mechanisms. Positive selection pressure on the I1017F mutation is moderate in field-collected T. urticae populations. Further studies are required to identify metabolic detoxification genes that confer resistance to MGIs for precise resistance monitoring.
AB - Mite growth inhibitors (MGIs), such as etoxazole and hexythiazox, are valuable IPM tools for Tetranychus urticae control in hops due to their unique mode of action and selectivity. Hence, it is necessary to standardize bioassay methods to evaluate the efficacy of MGIs, monitor resistance, and identify mechanisms underlying MGI resistance in the field. Here, we developed a three-tiered approach for evaluating ovicidal toxicity of MGIs to T. urticae, which simulated different MGI exposure scenarios in the field. The most effective bioassay method was direct exposure of T. urticae eggs to MGIs. With this method, four field-collected T. urticae populations showed low-to-moderate resistance to MGIs. Cross-resistance among MGIs and from MGIs to bifenazate and bifenthrin was detected. Besides target site insensitivity, enhanced cytochrome P450 and esterase activities also contribute to the MGI resistance in hop yard-collected T. urticae populations. Low-to-moderate MGI resistance in T. urticae populations may be mediated by multiple mechanisms. Positive selection pressure on the I1017F mutation is moderate in field-collected T. urticae populations. Further studies are required to identify metabolic detoxification genes that confer resistance to MGIs for precise resistance monitoring.
UR - http://www.scopus.com/inward/record.url?scp=85018428068&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85018428068&partnerID=8YFLogxK
U2 - 10.1017/S0007485317000414
DO - 10.1017/S0007485317000414
M3 - Article
C2 - 28464967
AN - SCOPUS:85018428068
SP - 1
EP - 12
JO - Bulletin of Entomological Research
JF - Bulletin of Entomological Research
SN - 0007-4853
ER -