Entomopathogens in conjunction with imidacloprid could be used to manage wireworms (Coleoptera: Elateridae) on spring wheat

Authors: ANTWI, FRANK - Montana State Extension Service; SHRESTHA, GOVINDA - Montana State Extension Service; REDDY, GADI - Montana State Extension Service; Jaronski, Stefan

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2017
Publication Date: 12/12/2017
Publication URL: http://handle.nal.usda.gov/10113/5922770
Citation: Antwi, F.B., Shrestha, G., Reddy, G.V., Jaronski, S. 2017. Entomopathogens in conjunction with imidacloprid could be used to manage wireworms (Coleoptera: Elateridae) on spring wheat. The Canadian Entomologist. 150:124–139. doi:10.4039/tce.2017.58.

Interpretive Summary: The soil-dwelling larvae of click beetles (wireworms) are serious pests of several agricultural crops worldwide, particularly in the “Golden Triangle”, an important cereal-growing region in Montana. Wireworm damage to this field crop in the region is increasing, because currently available pesticides provide only partial control and no alternative options have been developed. This study, conducted in replicated field trials in 2015 and 2016, sought to evaluate two commercial, insect pathogenic fungi, and several other biologicals and biorationals for the control of wireworms in Montana spring wheat. Results were inconsistent among replicate fields and years, but there were indications that the fungi, alone or combinations with imidacloprid, had significant impacts on plant stand protection compared to the controls. Azadirachtin, spinosad, Burkholderia spp. strain A396, and Chromobacterium subtsugae, seemed to provide no yield protection against wireworm attack.

Technical Abstract: The soil-dwelling larvae of click beetles (wireworms) (Coleoptera: Elateridae) are serious pests of several agricultural crops worldwide. Hypnoidus bicolor and Limonius californicus are two major wireworm species damaging to spring wheat, particularly in the Golden Triangle, an important cereal-growing region in Montana. Wireworm damage to this field crop in the region is increasing, as currently available pesticides provide only partial control and no alternative options have been developed. We examined the effect of biopesticides alone, their mixtures or in conjunction with a conventional pesticide (imidacloprid) against wireworms. Biopesticides tested were: 1) spinosad Saccharopolyspora spinosa, (2) Metarhizium brunneum, (3) M. brunneum F52, (4) Beauveria bassiana GHA, (5) azadirachtin, (6) B. bassiana ANT-03 (7) pyrethrin, (8) Chromobacterium subtsugae, and (9) Burkholderia spp. strain A396. The efficacy of biopesticides was based on crop stand protection, wireworm larval populations and grain yield. In the 2015 study, we found that entomopathogenic fungi alone or their combinations with imidacloprid had significant impacts on plant stand protection compared to water control. Applications of B. bassiana or a combination of M. brunneum F52 with imidacloprid protected wheat stand seedlings from wireworm damage better than water control at the Ledger location, while a combination of B. bassiana with M. brunneum F52 provided similar protection at the Valier location. Unexpectedly, wireworm larvae populations were found significantly higher on plots treated with B. bassiana, spinosad, M. brunneum F52 + spinosad, and M. brunneum compared to water control at 14 or 28 days post applications at the Ledger location, but without effects at the other location. We found significantly higher grain yield when plots treated with imidacloprid + M. brunneum F52 and B. bassiana + azadirachtin over water control at the Ledger location. In the 2016 study, there were no significant effects of treatments on studied parameters as compared to water control.