Monday, November 5, 2007 - 1:45 PM
77-3
How Much Does Corn Rootworm Damage Affect Corn Growth and Yield?.
William Cox, Elson Shields, Debbie Cherney, and Jerry Cherney. Cornell University, Crop & Soil Sci 620 Bradfield Hall, Cornell University, Ithaca, NY 14853
Western corn rootworm (Diabrotica virgifera virgifera Le Conte), which is more prevalent because of its isolated adaptation to crop rotation and increased 2nd year corn plantings, inconsistently reduces corn (Zea mays L.) yield so control is not always justified. A 2-yr NY field study using seed and soil-applied insecticide treatments was conducted to understand growth responses of corn to rootworm damage. The control had moderately severe (1.40, node-injury scale), whereas the 1.25 mg kernel-1 clothianidin [(E)1-(2-chloro-1, 3-thiazol-5-ymethyl)-3-methyl-2 nitroguanidine] treatment had minor (0.18) rootworm damage. The control vs. clothianidin had a lower leaf area index at the 12th leaf stage (2.80 vs. 3.18) but similar values at silking (4.59 vs. 4.76) and early grain-fill (4.30 vs. 4.64 m2 m-2, respectively). The control vs. clothianidin had lower crop growth rate from silking to early grain-fill (23.6 vs. 36.3) but similar rates from 12th leaf to silking (34.9 vs. 36.4) and early to late grain-fill (27.2 vs. 25.3 g m-2 d-1, respectively) stages. The control vs. clothianidin had less kernels m-2 (4423 vs. 4751) but similar kernel weight (257 vs. 248 mg) and harvest index (0.48 vs. 0.49 kg kg-1, respectively). The control vs. clothianidin had lower yield (9.7 vs. 10.6 Mg ha-1, respectively) but root damage ratings did not correlate with yield (r=-0.19, n=48). More research is required on the complex yield reduction-rootworm damage relationship to help growers use control measures judiciously.