Wireworm Management I: Stand Protection Versus Wireworm Mortality With Wheat Seed Treatments

Abstract

The efficacy of various insecticidal seed treatments in protecting wheat, Triticum aestivum L., from wireworm damage as well as reducing wireworm (Coleoptera: Elateridae) populations was studied over 3 yr. Protection from wireworm damage was measured by postplanting stand counts, and effects on wireworm populations were measured by within-row core samples and by bait traps placed in plots the following spring. The effects of treatments on populations of larger wireworms already present at planting were distinguished from their effects on neonate wireworms produced that growing season. Neonicotinoid seed treatments (imidacloprid, clothianidin, and thiamethoxam) provided excellent wheat stand protection, likely through prolonged wireworm intoxication, but populations of larger and neonate wireworms were not significantly reduced in bait traps the following spring. The pyrethroid tefluthrin, applied to seed with and without a neonicotinoid insecticide (thiamethoxam), provided excellent crop protection, but populations of wireworms also were not significantly reduced. This and additional laboratory data suggest that wheat stand establishment provided by tefluthrin is due to a combination of repulsion and short term morbidity events. The phenyl pyrazole fipronil provided excellent crop protection, and populations of both larger and neonate wireworms could not be detected in plots the following spring. The previously registered organochlorine lindane, although reducing wireworm feeding, was phytotoxic in 2 of 3 yr. Next to fipronil, lindane was the most consistent seed treatment in reducing populations of larger and neonate wireworms. These studies indicate that stand and yield protection provided by contemporary wheat seed treatments cannot automatically be equated with wireworm population mortality. This is an important consideration when choosing a suitable seed treatment to replace lindane, which historically provided both stand protection and wireworm reduction, and did not have to be applied every year.

Winter Wheat Yields Are Increased by Seed Treatment and Fall‐Applied Fungicide

“…Fungicide treatments with the active ingredient prothioconazole are purported to improve frost tolerance in wheat by modulating morphological changes to the mesocotyl, and tebuconazole purportedly causes physiological changes that improves root development (Anonymous, 2009). Vernon et al (2009) reported improved plant stands with imidicloprid and hypothesized this was likely due to wireworm (Coleoptera: Elateridae) control, but noted that toxic effects were temporary and not lethal; however, the improved plant stand may have been unrelated to biotic stress. Ford et al (2010) established that neonicotinoids such as imidacloprid and clothianinidin induce salicylic acid-associated responses, which elicits plant protection to pathogens such as powdery mildew concomitant with abiotic stress tolerance.…”

Control methods and monitoring of Agriotes wireworms (Coleoptera: Elateridae)

“…In accordance with van Herk et al (2008c), field efficacy studies suggest that wireworms may actually enter a long-term state of intoxication upon contact with clothianidin and imidacloprid and recover later on in the growing season. Further evidence is given by observations of Vernon et al (2009) who found that populations of wireworms were not significantly reduced in bait traps the spring after the application.…”

“…Applied as a wheat seed treatment, imidacloprid, clothianidin, and thiamethoxam provided an excellent stand protection, although wireworm population was not reduced (Vernon et al 2009). This has also been observed with imidacloprid seed dressings in simulated field studies on sugarbeet and maize for different Agriotes species (Furlan & Toffanin 1998).…”

“…Tefluthrin as a seed treatment of wheat provided excellent crop protection, but populations of wireworms were not significantly reduced (Vernon et al 2009). In soil bioassays, tefluthrin actually repelled A. obscurus (van Herk et al 2008b).…”

Pest Management Strategies for Potato Insect Pests in the Pacific Northwest of the United States

“…In furrow applications are also effective; however, some rotational restrictions may apply (Schreiber et al, 2010). Use of contemporary chemicals in other crops suggests that stand protection and wireworm reduction are not covered with current chemicals available (Vernon et al, 2009). …”