Evaluation of Insecticide Application Timing on Sorghum Midge Injury to Grain Sorghum, 1995

The test was conducted at the Macon Ridge Location of the Northeast Research Station in Franklin Parish, LA. Plots (28 ft X 8 rows) were planted on a Gigger-Gilbert silt loam on 15 Jun in a RCB design with 5 replications. Karate 1EC at 0.02 lb (AI)/acre was applied with a high clearance sprayer equipped with a CO2 charged system calibrated to deliver 9.3 gpa at 46 psi and 3.3 mph through TX-8 hollow-cone nozzles (2/row). Application timing for each treatment was determined by selecting and tagging 20 plants from the 2 center rows before spraying. For the 50% and 90% panicle emergence treatments, 10 and 18 plants, respectively, had panicles completely emerged with no open flowers. For the 20, 50 and 90% flowering treatments, 4, 10 and 18 of 20 tagged plants per plot, respectively, had flowering panicles. A panicle was considered to be flowering when the upper 25% portion had open spikelets. Treatments were applied on 28 Jul for the 50 and 90% panicle emergence and on 31 Jul for the 20, 50 and 90% panicle flowering. Sorghum midge damage to seed heads was evaluated on 24 Aug by estimating percent blasted kernels on each tagged plant. Sorghum seed yields were obtained on 8 Sep by manually harvesting panicles from the 20 tagged plants and by mechanically harvesting the entire 2 center rows in each plot.