lmazapyr, a new herbicide for use in rubber

Abstract

The effect of imazapyr (isopropylamine salt of 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-yl) nicotinic acid) on growth of rubber and control of weeds associated with the crop, was studied in trials carried out nursery, as well as in developing and mature rubber plantations. Imazapyr at dosages up to 0.75 kg active ingredient (a.i.) per hectare showed no effect on three-month-old rubber plants in the nursery trial. The grasses Paspalum virgatum, P.conjungatum and Digitaria horizontalis were controlled by imazapyr at dosages from 0.375 kg ia/ha. In young and mature rubber plantations, excellent control of Hydrocotylesp, Vernonia scorpioides, Clidemia sp, Wedelia paludosa, Scleria pterota and Paspalum sp was achieved with dosages of 0.5, 0.75 and 1.0 kg a.i./ha, with no phytotoxicity problems to rubber trees. It was concluded that imazapyr is a selective herbicide for rubber, and can be effectively utilized in young plantations at dosages up to 0.75 kg a.i./ha. In mature rubber plantations it can be used up to 1.0 kg a.i./ha, with good weed control for periods up to eight months.