Herbicidal efficacy and selectivity of imazethapyr for weed control in alfalfa (Medicago sativa L.) in Sudan

Abstract

Alfalfa, or lucerne (Medicago sativa L.), is a perennial and an important leguminous forage crop worldwide.  A field trial was conducted at Shambat Research Station Farm, Khartoum, Sudan, during the 2014/2015 and 2015/2016winter seasons to evaluate the activity and selectivity of the herbicide (imazethapyr) for weed control in alfalfa. The herbicide imazethapyr at 57.1, 76.2, 95.2, and 114.3 g a.i./ha was applied at sowing and 3 weeks later. The most prevailing weed species were Brachiaria eruciformis (Sm) Grieseb, Cyperus rotundus L., Ipomoea sp., and Tribulus terrestris. The herbicide imazethapyr, at all rates, irrespective of application time, gave good to excellent control (78–98%) of broad-leaved weeds. However, its activity against grasses was poor. All herbicide treatments significantly reduced weed biomass in comparison to the untreated control. All herbicide treatments were selective to the crop. Competing weeds reduced total dry matter yield by 36% in both seasons. Imazethapyr at all rates, irrespective of application time, resulted in total dry matter yield comparable to that of the weeded control.