Evaluation of ultra low volume deposition of public health insecticides in a hot desert environment

Three insecticides common for mosquito and sand fly control were applied 30 min to 3 h after sunset during June and July 2010, at Camp Buehring, Kuwait to determine the relative quantity, height and distance traveled in a hot desert environment. BVA dilution oil was used for the control.  Oil-based adulticides were sprayed using a truck-mounted Curtis DynaFog Maxi-Pro 4 ULV sprayer.  Fyfanon® ULV (96.5% malathion), Scourge® 4 + 12 (4% resmethrin), ULD BP-300 (3% pyrethrins) and BVA Spray 13 (100% refined petroleum distillate) were mixed with Caracid Brilliant Ravine FFS fluorescent dye and applied at two speeds on evenings when wind speed was less than 10 mph.  Collection targets using 1-m long, 2.5 cm wide biodegradable cotton ribbons were later read with a fluorometer to quantify the amount of insecticide deposited on targets set at heights of 6", 30" and 60"  and distances of 5', 20', 50', 100', 200' and 300'. Mean insecticide deposition across all distances was 31% on 30" targets and 49% on 60" targets while 6" targets typically collected < 20% of test spray. Mean ground temperatures were typically within 1°C of air temperatures at 60" and 1 to 2°C higher than air at 6" or 30".  Collectively, mean insecticide deposition was 79% at or above 30” for all insecticides.  This data may explain in part why control of low-flying phlebotomine sand flies with ULV insecticides has met with less than optimal success by U.S. military forces deployed in the Middle East.