Dissipation behavior of malathion and dimethoate residues from the soil and their uptake by garden pea (Pisum sativum)

Abstract

The dissipation of malathion and dimethoate from soil and their uptake by garden peas was studied in a greenhouse at 10-26°C. Twenty-one-day-old seedlings were treated with 50% EC malathion or 40% EC dimethoate, labelled with 14-C, at a rate of 15.53 µg/g. Dimethoate was more persistent than malathion in soil, with half-life values of 72 and 17 days, respectively. Faster dissipation of malathion was accelerated by degradation of bound residues, which would normally increase persistence in the soil. Malathion was not efficiently absorbed from the soil by pea plants due to its low solubility in water and high log Ko/w. Dimethoate was readily available to the pea plant by water mass flow through the xylem.