In this study, we investigated the degradation of pyriproxyfen, bifenthrin and the performance of a mixture of pyriproxyfen and bifenthrin [formulas of missile 10% EC and zedorale 10% EC (pyriproxyfen), dioxin 20% EC (pyriproxyfen + bifenthrin), and (bifenthrin) flux 20% EC (Emulsion Concentration). Fourteen days were spent storing the tested insecticides at 54±2°C. During the storage period, samples were taken after 14 days to determine physical properties, such as emulsion concentration, as basic properties and to evaluate the chemical stability of the active ingredient using high-performance liquid chromatography and fingerprint analysis (GC-MS and IR). As well as the evaluation of their efficacy, toxicology studies show a very minute shift in LC50 for both Spodoptera littoralis and Pseudococcus longispinus recorded before and after storage of the insecticides tested.
The obtained results showed that Pyriproxyfen's active ingredients were 9.95%, 9.86%, 9.83% and reached 9.81%, 9.72%, and 9.75% after 14 days of storage at 54±2°C for missile 10% EC, zedorale 10% EC, and dioxin 20% EC, respectively. While the active ingredients for bifenthrin in dioxin 20% EC and flux 20% EC were 9.93% and 19.692%, they reached 9.85% and 18.82% after 14 days of storage at 54±2°C, respectively. This result refers to the fact that missile 10% EC, zedorale 10% EC, and dioxin 20% EC are more stable than flux 20% EC. Stability at an elevated temperature was within the FAO limits for all sources before and after storage.
Then the other tested GC/MS was used for the degradation of pyriproxyfen and bifenthrin insecticides; the major degradation product in pyriproxyfen was 1-(4-phenoxyphenoxy) propan-2-ol, and the major degradation product in bifenthrin was 2-methyl[1,1'-biphenyl]-3-carbaldehyde.