Clothianidin Seed Treatments Inconsistently Affect Corn Forage Yield When following Soybean

Cool conditions after corn ( Zea may s L.) planting frequently delay emergence in the northeastern USA, which is conducive to damage by the soil insect pest, seed corn maggot ( Delia platura ). Two hybrids with three seed‐applied insecticide treatments, which included a control, 0.25 mg a.i. seed −1 clothianidin [(E)1‐(2‐chloro‐1, 3‐thiazol‐5‐ymethyl)‐3‐methyl‐2‐nitroguanidine], and 1.25 mg a.i. seed −1 clothianidin, were evaluated in 2004 and 2005 in New York. The objective of the study was to determine if clothianidin affects final plant densities, total dry matter (DM) accumulation during vegetative growth, DM yield, and forage quality in an environment with occasional soil insect pests. Corn emerged in 7 d in 2004 so clothianidin did not affect final plant densities, but the 1.25 mg a.i. treatment vs. the control of one hybrid had 1.3 Mg ha −1 greater DM yield. Corn emerged in 17 d in 2005, and the 0.25 mg a.i. treatment averaged 3296 more plants ha −1 while both clothianidin treatments vs. the control of one hybrid had 1.4 to 1.7 Mg ha −1 greater DM yields. Lack of negative responses of final plant densities, vegetative growth, and DM yield indicates that clothianidin seed treatments have no phytotoxic effect on corn. Nevertheless, seed treatments did not affect forage quality or calculated milk yields so our study indicates that clothianidin seed treatment is not justified when corn follows soybeans [ Glycine max L. ( Merr )] in the northeastern USA.