Pest Management Science (2021) 77, 4572-4582

James L. Maino, Ary A. Hoffmann, Matthew Binns, Xuan Cheng, Anthony van Rooyen and Paul A. Umina (2021)
Strip spraying delays pyrethroid resistance in the redlegged earth mite, Halotydeus destructor: a novel refuge strategy
Pest Management Science 77 (10), 4572-4582
Abstract:
BACKGROUND
Pesticide resistance has seen control options for the redlegged earth mite (RLEM), Halotydeus destructor, dwindle for Australian grain farmers. The recent discovery of high recessiveness for pyrethroid resistance in RLEM provided an opportunity to examine the feasibility of a refuge strategy to slow the evolution of resistance. Unlike lepidopterous pests in Bt crops, where refuge strategies are routinely practiced, RLEM is a slow-moving pest, which will impact the design of susceptible refuges.
RESULTS
Firstly, we confirmed the pyrethroid resistant allele is recessive to the susceptible (wildtype) allele (in terms of resistance) across spatially separated Australian populations. Secondly, we demonstrated that a small, localized resistant mite population can revert to susceptibility at field relevant scales and conditions. Next, we used a simulation modelling approach to design a practical refuge strategy to maintain susceptibility to pyrethroids in populations with a low incidence of resistance. Certain configurations (e.g. a pesticide strip width of 50 m and refuge spacing of 10 m) maintained low levels of resistance across a 10-year time horizon, with lower mite abundance and minimal yield loss. A larger refuge proportion did not always delay resistance, and, under certain conditions, increased resistance frequency.
CONCLUSION
Strip spraying to maintain refuges can be readily incorporated into RLEM management programs where sprayer widths in commercial cropping contexts are typically between 20–40 m. A refuge approach to RLEM management that uses strip spraying may enhance long term control options in the absence of new chemical registrations but will now require field validation.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Ary A. Hoffmann, Paul A. Umina

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Halotydeus destructor		Australia (South+SE)