Diurnal leaf movement effects on spray interception and glyphosate efficacy

Time of day at which a herbicide is applied can affect efficacy, and variab ility may be attributed to leaf angles at application. Spray interception b y hemp sesbania (Sesbania exaltata), sicklepod (Senna obtusifolia), and pri ckly sida (Sida spinosa) under day and night conditions was quantified by m easuring interception of a 2-M potassium nitrate solution. Following the ni ght application, interception by prickly sida, hemp sesbania, and sicklepod was reduced 17, 67, and 70%, respectively. In a second study in the greenh ouse, glyphosate was applied to hemp sesbania, pitted morningglory (Ipomaea lacunosa), prickly sida, and sicklepod at 6:00 and 11:00 A.M, and 4:00 and 9:00 P.M. Control of all species was dependent on the time of day treated, with night applications generally being less effective.