STORE TIME OF PERMETHRIN IN THE TRUCK-MOUNTED ULV SPRAY TANKS CAUSED DEGRADATION IN THE CONCENTRATIONS

Permethrin is one of the few active ingredients found in commercial adulticides available for adult mosquito control. The permethrin concentrations in the adulticide Aqualuer 20-20 formulation stored in the 21 ultra-lowvolume (ULV) truck-mounted spray tanks after 4, 6, and 8 months were sampled and analyzed by gas chromatography mass spectroscopy (GC-MS). Additionally, the permethrin stored in a mixing pump and a stock container were sampled and analyzed by GC-MS. The results showed that 46%, 42%, and 82%, permethrin in Aqualuer 20-20 were decomposed in the ULV spray tanks at 4--, 6--, and 8 months-storage, respectively. For the mixing pump, 17% of the permethrin in the Aqualuer 20-20 were decomposed. The storage time of permethrin in ULV spray tanks resulted in the degradation in the concentrations of permethrin after more 4 months, compared with the concentration in stock control. The degradation of permethrin in ULV spray tanks may directly impact the control efficacy for adult mosquitoes and result in an economic loss.