Does prophylactic seedling insect management protect against early season pest damage in Bt and non-Bt Maryland corn?

Corn growers may combine tactics for at-planting pest control, including insecticides and hybrids expressing plant-incorporated protectants. These approaches target a complex of above- and below-ground pests that can reduce plant populations, although these pest targets overlap. While seedling pest control is often crucial because of the cost of replanting, these treatments may be redundant, adding unnecessary costs. Seedling pests in Maryland tend to be sporadic and at-planting insecticides may also negatively impact natural enemies. Maryland growers rate slugs a top concern, so tactics that harm slug natural enemies may be especially problematic. To understand the pest management value of prophylactic management tactics, we compared a neonicotinoid seed treatment (NST, clothianidin) and an in-furrow pyrethroid (IFP, bifenthrin) in Bt and non-Bt corn at three research farms in Maryland. We quantified stand count, seedling damage, slug and slug predator activity-abundance, predation rates, and yield. In the first two years of the three-year study, insect pest pressure tended to be lowest in the NST treatment, though it rarely reached treatment thresholds and treatments did not impact yield. The IFP only reduced pests in non-Bt corn. Slug pressure and natural enemy predation on sentinel prey did not differ suggesting that treatments do not disrupt slug biocontrol. Although they did not demonstrate non-target impacts, the lack of economically important pest pressure indicates that prophylactic treatments may not be justified. Implementing efficient, economically and environmentally sustainable corn pest management requires a thorough understanding of the contributions of each component of the pest control system.