Abstract
Abstract Performance of granular and liquid insecticides against BCW was evaluated with artificial infestations at the Rosemount Experiment Station, Rosemount, MN. Treatment plots, each measuring 4 rows (30-inch spacing) × 50 ft, were established in corn planted on 2 Jun. Treatments were arranged in a randomized complete block design with 4 replications. Granular insecticides were applied in a 7-inch band ahead of the presswheel or in furrow at planting with modified Noble applicators mounted on a John Deere 7100 MaxiMerge planter. When corn reached the 2-leaf stage a central portion of each plot (2 rows × 15 ft) was enclosed by an aluminum barrier buried 3-4 inches into the soil that projected 4 to 5 inches above soil level. Plant population within the barriers was thinned to 23,900 plants/acre. Liquid insecticides were broadcast on 15 Jun am using a CO2-powered backpack sprayer calibrated to deliver 21 gal/acre at 25 psi through 8002 nozzles. During application, air temperature averaged 77°F and winds ranged from still to 2 mph. Each plot was infested with a mixture of 40 third and fourth instar black cutwork larvae on the evening of 15 Jun and early morning of 16 Jun. Plots were examined every 2-3 d for leaf feeding and cutting. Cut plants were marked with a plastic stake to avoid misses or recounts as undamaged plant on later visits. On 27 Jun (11 d after infestation), each plot was censused with the number of injured plants and dead plants recorded. Before analysis, percentage data were subjected to an arcsine transformation.
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