Laboratory degradation studies were performed in water at pH 4.0, 7.0 and
9.2 using methomyl (Lannate 12.5 L) formulation at the rates of 1.0 (T1) and 2.0 (T2)
μgmL
-1
. Water samples collected on 0 (2 h), 3, 7, 15, 30, 45, 60 and 90 days after
treatments were processed for residue analysis of methomyl by HPLC equipped with
Photo Diode Array Detector. In 60 days, dissipation was 84-87% at pH 4.0, 71-77% at
pH 7.0, and 91-93% at pH 9.2 in both treatments showing very little effect of pH on
dissipation. The half-life periods observed were 20.76 and 22.13 days at pH 4.0, 27.87
and 28.67 days at pH 7.0 and 15.84 and 16.54 days at pH 9.2 at T1 and T2 doses
respectively.
