Rotation, distance, and insecticide resistance in Colorado potato beetle

• 2007 annual report

The problem is the evolution of resistance to neonicotinoid insecticides (Admire®, Provado®, Platinum®, Actara® and others) due to their consistent and ubiquitous use for control of Colorado potato beetle in Long Island and elsewhere in the Northeast. The rapid evolution of resistance on Long Island (Olson et al 2000) has discouraged most growers from applying in-furrow and foliar imidacloprid in single fields. However, most growers in the region apply imidacloprid in-furrow at planting, and have done so for at least nine years (Dale Moyer, personal comment). In this project I will work with growers on Long Island to measure the effects of crop rotation with and without imidacloprid treatment. Insecticide resistance in general increases costs to growers (Grafius 1997) and leads to higher application rates and unintended environmental damage. High levels of resistance to neonicotinoid insecticides are a particular threat to growers on Long Island because the number of alternative treatments is more restricted because of watershed protection and because of the reliance of growers on imidacloprid. Loss of perceived effectiveness of imidacloprid has also led to heavy use of spinosad, which has led to at least one case of significant resistance to spinosad as well (Baker, unpublished data from 2006 NESARE project). The presence of at least three alternatives to imidacloprid--Spinosad, Novaluron and Kryocide--should in theory help with resistance management and relieve pressure on imidacloprid. However, Kryocide is less preferred due to expense and inconvenience, and selection for resistance to Spinosad has been correlated with increased resistance to imidacloprid as well (Baker, unpublished data from 2006 NESARE project).

My proposed solution is to combine both crop rotation and insecticide rotation to preserve imidacloprid effectiveness and reduce total insecticide application rate. This is not a new idea, but it needs better quantitative support to be widely adopted. This strategy would take advantage of persistent costs of resistance to imidacloprid that act to reduce resistance within and between seasons. Crop rotation is a proven method to reduce colonizing insect populations (Wright 1984, Lashomb et al. 1984, Sexson and Wright 2005, Weisz et al. 1994). Crop rotation can indirectly (Roush et al 1990) and possibly directly help reduce resistance as well. This project will test the hypothesis that imidacloprid-resistant CPB are less likely or able to fly long distances when colonizing new fields in the spring. If this hypothesis is true, then colonizing CPB collected farther from their emergence sites should be less resistant than those collected closer to those sites. Further, flying emergers are predicted to be less resistant than walking emergers. Finally, fields rested from potato the previous season should be colonized by less resistant CPB than fields previously in potato with local emergers overwintering from last year’s crop. If these predictions are true, a three-year cycle--first away from potato, and then with potato but away from in-furrow application of imidacloprid, then with imidacloprid at planting and away from spintor--can protect against insecticide resistance and reduce total pesticide use.