Strip spraying delays pyrethroid resistance in the redlegged earth mite, <i>Halotydeus destructor</i> : a novel refuge strategy

BACKGROUND Pesticide resistance has seen control options for the redlegged earth mite (RLEM), Halotydeus destructor, dwindle Australian grain farmers. The recent discovery of high recessiveness pyrethroid in RLEM provided an opportunity to examine feasibility a refuge strategy slow evolution resistance. Unlike lepidopterous pests Bt crops, where strategies are routinely practiced, is slow-moving pest, which will impact design susceptible refuges. RESULTS Firstly, we confirmed resistant allele recessive (wildtype) (in terms resistance) across spatially separated populations. Secondly, demonstrated that small, localized population can revert susceptibility at field relevant scales and conditions. Next, used simulation modelling approach practical maintain pyrethroids populations with low incidence Certain configurations (e.g. pesticide strip width 50 m spacing 10 m) maintained levels 10-year time horizon, lower abundance minimal yield loss. A larger proportion did not always delay resistance, and, under certain conditions, increased frequency. CONCLUSION Strip spraying refuges be readily incorporated into management programs sprayer widths commercial cropping contexts typically between 20–40 m. uses may enhance long term absence new chemical registrations but now require validation. © 2021 Society Chemical Industry.