Ultra-Low-Volume Aerial Spraying of Dieldrin and Malathion for Rangeland Grasshopper Control12

Abstract

During 1962, in Montana, ultra-low-volume dieldrin sprays were applied against range grasshoppers by Piper Pawnee® aircraft equipped with British-made Micronair Rotary Atomizers® or with standard boom and nozzles. Dieldrin at ¾ oz/acre in 1 pt or 1 qt of diesel fuel gave mortalities equal to the same dosage in 1 gal. The standard boom and nozzle appeared to give results equal to those obtained from the Micronair. In 1963 additional tests with the boom and nozzle equipment were carried out in California with large aircraft (TBM) on 1280-acre plots and Stearman® aircraft on 160-acre plots. Dieldrin at ½ oz/acre in 1 pt, 1 qt, 2 qt, or 1 gal of diesel fuel gave satisfactory kill where proper coverage was obtained. Coverage was somewhat better with the Stearman than with the large TBM, but with cither aircraft grasshopper mortality did not differ among treatments except on plots with dense stands of a species of sedge. In further tests malathion applied at the rate of 12 oz (actual) in 1 qt of Panasol® or in 1 qt or 1 gal of water gave equal and satisfactory kill when applied to 160-acre plots with Stearman aircraft. At Twin Falls, Idaho, technical malathion was applied at ⅝ pt (12 oz actual) / acre on 3 160-acre plots by Stearman aircraft. A single plot of 1830 acres was treated with technical malathion at ½ pt (10 oz actual) /acre with the same equipment. Results of these tests were generally satisfactory. In replicated tests malathion was applied to 160-acre plots at dosage rates of 12, 9, and 6 oz actual in 1 pt and 1 qt of Panasol/acre. Results were generally satisfactory except at the 6-oz dosage. No differences in kill were noted between volumes of 1 pt and 1 qt. The economic value of ultra-low-volume applications by aircraft and some factors affecting the success or failure of the method are presented.