Products Evaluated for Corn Rootworm Management

Materials and Methods 2005 Sutherland test. Plots were planted on May 6 in an area that had been a corn rootworm beetle “catch crop,” with high populations of late-planted corn the previous year. The experimental design was a randomized complete block with one-row treatments, 50 ft in length, replicated four times. A four-row John Deere 7100 planter with 30-in. row spacing was used to plant the plots at 29,900 seeds/acre. Specially designed seed hoppers with standard “finger pick-up mechanisms” were used to handle the small amounts of prebagged seed. DKC60-18, was the corn hybrid used for the YieldGard Plus treatments (transgenic seed containing a Bt protein). The seed treatments (high rates for corn rootworm) were commercially applied to DKC60-19, the non-Bt equivalent of the transgenic seed. The non-Bt seed was also used with the granular and liquid insecticide treatments. Liquid Regent 4SC microtube treatments were applied at 4 gpa of finished spray. Capture 2EC, Lorsban 4E, and Lorsban 75WG liquid treatments were applied at 5 gpa. On July 25, following the majority of corn rootworm feeding, corn-root systems were dug, washed, and rated for injury on the Iowa State node-injury scale: 0.00 equals no feeding; 1.00 equals one node (circle or roots), or the equivalent of an entire node, eaten back to within approximately 1.5 in. of the stalk (or soil line if roots originate from above-ground nodes); 2.00 equals two nodes eaten; and 3.00 equals three nodes eaten. Damage caused by eating in between complete nodes is noted as the percentage of the node missing (e.g., 1.25 = 1 1/4 nodes eaten). A product consistency (%) was also calculated for each treatment. Product consistency equals the percentage of times a treatment limited feeding injury to 0.25 node or less. Plant stand and lodging counts were taken from 17.5 row-ft in each row. Yields were not calculated in this test.