Wireworm management: mitigating environmental risk with the developmentof new ‘push-pull’ strategies


Abstract: Many higher risk insecticides commonly used for wireworm management are nowobsolete worldwide, or soon will be, and wireworm populations and damage are on the riseglobally. The search for lower risk replacements, however, has proven to be challenging. Ourstudies, for example, have shown that neonicotinoids (i.e. thiamethoxam, clothianidin andimidacloprid) applied as seed treatments (i.e. wheat, corn, potatoes) will preserve crop stand andyield, but this is due to wireworms entering a long-term but reversible state of intoxication ratherthan mortality. We have also found that synthetic pyrethroids (i.e. bifenthrin and tefluthrin)applied as wheat seed treatments are repellent to wireworms long enough to enable cropestablishment, but once again without wireworm mortality. In contrast, the phenyl pyrazol,fipronil, applied at higher dosages to wheat seed and potato crops resulted in excellent cropprotection and near extermination of wireworm populations. Applications of fipronil at lowerdosages did not affect wireworm health immediately, but significant latent mortality (up to 90%)began occurring after about 40 days. Since fipronil has a higher environmental and health riskprofile than the neonicotinoids or pyrethroids, a number of novel strategies were developed toreduce the amount of fipronil applied per ha while maintaining crop health and significantlyreducing wireworms. A ‘blend’ of thiamethoxam (10g a.i./100kg seed) + fipronil (1g a.i./100kgseed) on wheat seed was found to be sufficient to protect wheat stand under moderate to highwireworm populations, as well as reducing neonate and resident populations by >90% (fipronilrate/ha = 1.24g a.i.). Similar field efficacy was also demonstrated with ‘push-pull’ strategiesinvolving 1:1 mixtures of ‘repulsive’ tefluthrin-treated wheat seeds and ‘lethal’ blend-treatedwheat seeds (fipronil rate/ha = 0.62g a.i.). Push-pull strategies to merely remove wireworms fromfields, or for use as companion plantings were developed using up to 3:1 mixtures of untreated(attractive) wheat seeds and blend-treated wheat seeds (with 3:1 seed ratios, fipronil rate/ha =0.095g a.i.). Practical uses for these strategies are discussed.

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