Corn Rootworm Larval Control, 1995

Two insecticide efficacy studies for controlling mixed populations of NCR (17% Experiment I and 42% Experiment II) and WCR (83% Experiment I and 58% Experiment II) were conducted at the Russell E. Larson Agricultural Research Center at Rock Springs, Centre County, PA. The experiments were conducted on separate fields approximately 1 mile apart. Corn was planted no-till on 16 May in both experiments using a John Deere Max-Emerge 2 row planter with 30-inch row spacing. The Lorsban 4E with 9-18-9 fertilizer in solution was applied at each site 22 May. Rain prevented application of this treatment earlier. Insecticides were applied to 5X40 ft plots in a RCB design with 4 replications per treatment. Plant populations were counted 15 Jun at both locations to identify seedling emergence and phytotoxicity that may have resulted from the treatments. Root damage ratings were evaluated 21 Jul (Experiment I) and 25 Jul (Experiment II) using the Iowa 1 to 6 system. Yields were determined in Experiment I as silage using a silage harvester on 12 Sep. One row of corn was harvested per plot and the row harvested was in the same relative position in all plots. Yield in Experiment II was determined by mechanically harvesting each plot for shelled corn on 23 Oct. Percent moisture in the silage plots was determined by drying a subsample (at 2.0 lb wet) from each plot and silage yield was adjusted to 65% moisture. Percent moisture in the shelled corn was determined for each plot with a moisture meter and yield was adjusted to 15.5% moisture.