The effect of clothianidin seed treatments on corn growth following soybean

Cool soil conditions after planting frequently delay corn (Zea mays L.) emergence in the northeastern United States, which contributes to occasional early-season soil insect damage. Two corn 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-thiazolyl-5-ymethyl)-3-methyl-2-nitroguani- dine], and 1.25 mg a.i. seed(-1) clothianidin were evaluated in 2004 and 2005 in New York to determine how clothianidin affects corn growth and yield in an environment with low incidence of soil insect pests. Both clothianidin treatments had greater leaf area index (LAI) values (similar to 2.60) at the 10th to 11th leaf stage (V10-11) compared with the control (2.45). The 0.25 mg a.i. rate had a greater LAI (4.46) than the 1.25 mg a.i. rate (4.28) at the silking stage (R1) and a greater mean crop growth rate from the V10-11 to R1 stage (36.5 and 32.7 g m(-2) d(-1), respectively). The control had a greater harvest index (0.54) than the 1.25 mg a.i. rate (0.50), but all three treatments had similar grain yield (9.7-10.3 Mg ha(-1)). Results from this study indicate that clothianidin seed treatments do not have phytotoxic effects on corn growth and yield in an environment with low incidence of soil insect pests. Nevertheless, we do not recommend clothianidin seed treatment as inexpensive insurance against early-season soil insect damage when corn follows soybean [Glycine max (L.) Merr.] in the northeastern United States.