Sensitivity of Melon [Citrillus colocynthis (L.) Schrad] and Weeds to Doses of Pre-Emergence Herbicides

Abstract

This study was conducted between 2014 and 2015 to determine the sensitivity of melon and weeds to selected pre-emergence herbicide rates in a humid agro-ecology zone of Nigeria. The field trial had thirteen treatments consisting of : seven rates of Primextra [Primextra-Gold^® (atrazine (370 g/l) + Metolachlor (290 g/l SC)], Raft (Terbutylazine 250g/L + Atrazine 250g/L)  at 2.0 kg ai ha^-1 , ForceTop (Pendimethalin 500g/L) at 2.0 kg ai ha^-1, and three weeded control and a weedy check.   Results from this study showed that melon and weeds were significantly sensitive to the herbicide rates. While the herbicide treatments had between 31-100% mortality depending on rate of the herbicide applied, the hand weeded treatments recorded between 19% and 60% melon mortality. Primextra at lower rates had similar effect on weeds as the weeded control, and gave good growth of melon. Primextra at 1.98kg a.i/ha, Force top at 2.0kg/ha and Raft at 2.0kg a.i/ha gave acceptable (≥ 70 %) weed control but caused lasting and unrecoverable injury. Melon may tolerate ≤ 1.00kgai/ha of Primextra, and may be susceptible to phytotoxic rates above 1.0 kg ai/ha. All herbicide rates above 1.0kg/ha gave acceptable (≥70%) weed density and biomass reduction. The importance of the present study is that farmers can intercrop maize and with Primextra Gold applied pre-emergence at a rate ≥ 0.25k ai/ha but ,< 0.5kg ai ha or relay melon into maize or any piece of land treated with  Primextra at  rates not exceeding 1.5 kg/ha at about 10 days after application.

Keywords: Herbicides, Phytotoxicity, Melon, and Weed