Northern and Western Corn Rootworm Adult Emergence and Root Injury Ratings Relative to Planting- Time and Post-Emergence Applications in Eastern South Dakota, 1994

A dryland field near Aurora, SD, was chosen to assess northern and western corn rootworm adult beetle emergence from planting-time and post-emergence insecticide treatment corn. Additionally, efficacy in preventing larval root injury was evaluated. The site had been continuously planted to corn for at least 5 years prior to the 1994 growing season. Individual treatment plots (single 15.2-m long rows spaced 96.5 cm apart) were arranged in a RCBD with 4 replications. Pioneer IR-3751 (100- day) corn seed was planted at approximately 23,000 kernels per acre. Planting-time granular formulations were applied using Noble metering units mounted on a modified Kinze 4-row corn planter, and all units were calibrated on the planter prior to insecticide applications. Banded granular treatments were applied in an 18-cm swath in fromt of the furrow-closing wheels, and incorporated by the wheels and drag chains. All planting-time applications (banded and in-furrow) consisted of directing insecticides immediately between double-disk furrow openers and into the open seed furrow. Post-emergence banded applications of Furadan 4F were placed over the row in 18- to 20-cm swaths using a single-nozzle (Teejet 8003 flat fan) boom. Broadcast ("Broad") liquid treatments were applied with a 1.8-m boom equipped with 4 Teejet 8003 flat fan nozzles spaced 46 cm apart. Liquid formulations (planting-time and post-emergence rescue) were applied using a CO2-powered canister spray system calibrated to deliver 20 gpa at 3 mph. All postemergence treatments were applied at cultivation time, and those that received cultivation following application were incorporated using a 2-row John Deer cultivator. Five roots per replicate were dug, washed, examined for feeding damage and rated using the Iowa 1 to 6 scale. Prior to rootworm beetle emergence, 2 cages (0.6 m wide by 1.0 m long by 15.2 cm high) were placed (equidistant from each other and the end of the plot) over each treatment row. The exterior rectangular frame base of each cage was constructed of 26-gauge galvanized steel and the top was made of aluminum screening material (45-mesh per cm2). A plastic cylindrical capture device was positioned at the apex of each screened pyramid to capture the emerged beetles. An inverted aluminum screen cone was fastened on the bottom side of each capture device to prevent beetle re-entry into the cage, and a small piece of “No Pest Strip” material was placed inside the device to kill captured beetles. Cages were monitored at weekly intervals for 6 wk. Monitoring consisted of collecting all beetles for the respective treatments from each replicate, and returning them to the laboratory for identification by species. Root rating and emergence data were analyzed using SAS’s General Linear Models procedure with treatment means being compared by DMRT.