Effects of imidacloprid seed treatments on crop yields and economic returns of cereal crops

Abstract

In the Pacific Northwest United States, cereal crops (barley, oats, wheat) are the foundation of most dryland crop rotations. Nearly 100% of cereal producers use neonicotinoid seed treatments to manage wireworms, regardless of crop and pest density. However, wireworms cause variable damage to different crops, and whether neonicotinoids boost yield and economic returns across crops remains largely unknown. In a field experiment conducted on one commercial farm over two years, we examined effects of imidacloprid seed treatments on wireworm density, yield, and economic returns for barley, oat, and wheat crops. Wheat plots with imidacloprid seed treatments produced greater yields and economic returns over costs than untreated plots, even though wireworm densities were largely unaffected by treatments. However, no differences in yield and economic returns were observed between treatments in barley or oats. Wireworm densities were markedly lower in oats compared to barley and wheat, indicating not all crops provided a permissive environment for wireworms. Our results support the hypothesis that growers may benefit from moving away from applying seed treatments in all cereal crops, but rather targeting management to specific crops, although research at more commercial farm sites remains needed to test the generality of this conclusion. Our results also support the hypothesis that incorporating more tolerant cereal crops (barley and oats) into rotations to replace spring wheat may be a promising option for growers in areas with high wireworm pressure.