Effects of imazaquin in the control of Euphorbia heterophylla weed in Vigna unguiculata (L.)

Abstract

Cowpea in its initial growth phase suffers from weed interference. Use of herbicide is becoming widespread in cowpea production. Euphorbia heterophylla Linn has defied most herbicides; metolachlor, pendimethalin and metobromuron, commonly used in cowpea do not control the weed. Imazaquin and some herbicides have shown some level of control of the weed in late application. There used to be some the potential loss in herbicide efficacy when applications are delayed. The objective of this study is to assess the effectiveness of early and late post - emergence application of imazaquin in the control of wild poinsettia in cowpea. In the combined analysis, use of imazaquin at 0.125 and 0.25 kg a.i./ha resulted in similar cowpea height, pod dry weight (10.0 and 12.1g/pot), numbers of leaves (13.8 and 15.3) and branches per plant (1.8 and 2.6) respectively, and number of days to 50% flowering. Weed control efficacy, weed population and weed dry weight per pot were similar irrespective of the two rates of application. Early post-emergence application of imazaquin resulted in greater number of leaves (20.3 and 8.8) and number of branches per cowpea plant (3.42 and 0.92); better weed control efficacy (73.3 and 24.9 %), lower weed population and lower weed dry weight as well as greater pod dry weight per pot (15.1 and 7.1 g/pot) respectively. Early pre-emergence application at 10 days after sowing of imazaquin at 0.125 kg a.i./ha is therefore recommended for the control Euphorbia heterophylla in cowpea plots.