Residual Behavior of Malathion and its Metabolite Malaoxon in Four Varieties of Mango Fruits

The degradation rates and residue levels of malathion as an insecticideand its metabolite malaoxon were studied on field grown four varieties of mango trees(Alfouns, Zebdia, Fajeri Klan, and Langra). The samples were collected after one hour, 1, 3,5, and 7 days post insecticide application. The data showed that the recovery rates ofQUCHER method were satisfied for both malathion and malaoxon. The obtained rates ofrecovery were 97 and 99% for malathion and malaoxon, respectively. The obtained residuesof both compounds under investigation (malathion and malaoxon) decreased gradually withtime, whereas, and there were no residues found 5 days later for malathion. Also, malaoxonshowed the same pattern of degradation thus it disappeared after 3 days from treatment. Thehalf-life time values of malathion (LT50) ranged from 0.96 to 2.8 days in these four mangovarieties while they were ranged between 0.43 to 0.9 days for malaoxon. The pre-harvestinterval (PHI) for each compound was determined according to their maximum residue limitswhich were 3 and 2 days for malathion and malaoxon, respectively on all four varieties ofmango fruits.