William J. Cox, Elson Shields, Debbie Cherney, and Jerry Cherney. Cornell Univ., Dep. of Crop & Soil Sci., 620 Bradfield Hall, Ithaca, 14853
Western corn rootworm (Diabrotica virgifera virgifera Le Conte) is the major insect pest in the corn phase of a corn (Zea mays L.) silage-perennial forage rotation. Dairy producers may prefer seed-applied instead of soil-applied insecticides for rootworm control because of additional control of other soil insect pests. The objective of the 2-yr NY field study was to evaluate Poncho [(E)1-(2-chloro-1,3-thiazol-5-ymethyl)-3-methyl-2 nitroguanidine] and Cruiser (3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine) at the 1.25 mg a.i. kernel-1 rate for rootworm control, dry matter (DM) accumulation, DM yield, and silage quality. The control had moderately severe (1.40-node injury scale), whereas Poncho (0.18) and Cruiser (0.39) had acceptable rootworm damage ratings. Poncho had greater DM accumulation at the 12th leaf stage (384 g m-2) compared with Cruiser and the control (324 g m-2), greater DM accumulation 3 weeks after silking (1491 g m-2), and greater DM yield (18.5 Mg ha-1) compared with the control (1245 g m-2 and 17.0 Mg ha-1, respectively). Cruiser had similar DM yield (17.4 Mg ha-1) but greater milk Mg-1 (1559 kg Mg-1) compared with Poncho (1475 kg Mg-1), Poncho had greater calculated milk yield (27301 Mg ha-1) compared with the control (25411 Mg ha-1) but similar to Cruiser (27192 Mg ha-1). We recommend Poncho for rootworm control in continuous corn silage fields in New York because of greater calculated milk yields but dairy producers may select Cruiser because of acceptable rootworm control and greater milk Mg-1.
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