Persistence and degradation of monocrotophos in cabbage.

Foliar application of monocrotophos in cabbage resulted in high initial residues of 6.00 and 7.54 microg g(-1) for the recommended dose (2 mL L(-1)) and double the recommended dose of monocrotophos (4 mL L(-1)) respectively. However, in farmer's practice treatment, it was found to be 2.54 microg g(-1) where it was sprayed once as fourth spray. Monocrotophos residues in cabbage after spray persisted for more than 30 days at both recommended and double the recommended dose of monocrotophos. The farmer's practice showed persistence of monocrotophos for only 15 days. Degradation of monocrotophos residues in cabbage followed first order exponential equation. Monocrotophos residues in cabbage degraded with a half-life of 2.87 to 3.05 days for four sprays at the recommended and double the recommended level of application. However, showed a half-life of 1.99 days for one spray of monocrotophos according to farmer's practice. Waiting periods /safe intervals for monocrotophos on cabbage were found to be 13.79, 15.90 and 8.55 days for the recommended, double the recommended dose and farmer's practice of monocrotophos application respectively.