Unprotected Indiana corn suffers no pest pressure...until year 4

The increasing information on the non-target effects of using neonicotinoid seed treatments (NST) on beneficial insects has made it essential to understand what benefits they provide to growers to assess whether they are necessary in a cropping system. Indiana, a top 5 state in corn production, provides an ideal environment to test whether pest pressure is consistent enough to require the continuous use of NST that is the norm. Paired fields of non-GMO corn were either coated with thiamethoxam as a seed treatment or left unprotected from 2017-2020 and evaluated for both early- and late-season pest damage using stand counts and root evaluations respectively. Plot yield was used to compare if any pest damage resulted in yield suppression or any benefit came from the use of NST. Across all sites from 2017-2019 almost no pest damage was observed and no NST-associated difference in yield was seen. However, in 2020 several fields without NST experienced root-feeding serve enough to cause lodging in several plants sampled. Even in the instances where corn expereinced insect damage, no yield loss was observed when comparing +/- NST. These results demonstrate that, while infrequent, continuous and unprotected corn in the Midwest could be vulnerable to pest damage. NST however do not match this occasional pressure and other integrated pest management principles such as crop rotation and scouting can likely ensure yield protection.