Abstract Twelve Lorsban 4 E (chlorpyrifos) treatment regimes for control of sorghum midge and an untreated control were compared in an experiment planted on the Texas A & M University Agricultural Research and Extension Center Farm at Corpus Christi. Sorghum plots 4-rows by 30-ft were planted 14 Apr on 38-inch row centers. Treatments were arranged in a randomized complete block design with 4 replications. Lorsban 4 E treatments were applied with a CO2-pressurized backpack sprayer calibrated to deliver 8.2 gal total spray volume/acre through size 3X hollow-cone nozzles (3 nozzles/row) at 44 psi. Initial treatments were made on 13, 16 and 19 Jun corresponding to panicle bloom stage. Therefore, treatments were based on 2 factors: (1) panicle bloom stage (10, 40 or 70%) and (2) number of treatments (1, 2, 3 or 4) applied at 3-day (72-h) intervals. This arrangement resulted in 12 insecticide treatment combinations. Two untreated rows served as a buffer between each 2 treated rows in each plot. Treatment effects were measured by visually estimating the percentage of midge damage to sorghum panicles on 13 Jul and harvesting 13.75 ft row from each of the center 2 rows in each plot on 24 Jul. Grain was removed from the panicle with an Amaco brand plot thrasher and grain weight was corrected to that corresponding to 14% moisture.