Western Corn Rootworm Damage Subtly Affects Corn Growth under Moderate Environmental Stress
2008
Cox, W. J. | Shields, E. | Cherney, D. J. R.
Western corn rootworm (Diabrotica virgifera virgifera Le Conte) is more prevalent because of its increased adaptation to crop rotation and increased continuous corn (Zea mays L.). A 2-yr field study using seed and soil-applied insecticide treatments evaluated growth responses of corn to rootworm damage. The control had moderately severe (1.40 on a 0–3 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 at silking (R1 stage). The control vs. clothianidin had a lower leaf area index at the 12th leaf (V12) stage (2.80 vs. 3.18) but similar values at R1 (4.59 vs. 4.76) and early grain-fill (R3) stages (4.30 vs. 4.64 m² m⁻², respectively). The control vs. clothianidin had a lower mean crop growth rate from R1 to R3 (23.6 vs. 36.3) but similar rates from the V12 to R1 (34.9 vs. 36.4) and R3 to late grain-fill (27.2 vs. 25.3 g m⁻² d⁻¹, respectively) stages. The control vs. clothianidin had less kernels per square meter (4423 vs. 4751) but similar kernel weight (257 vs. 248 mg) and harvest index values (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). The relationship between corn rootworm damage and corn growth was subtle and inconsistent across growth stages, but the control consistently yielded 8 to 9% less than the clothianidin treatment.
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