Field corn response to diclosulam

Authors: PROSTKO, E - University Of Georgia; Webster, Theodore

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2015
Publication Date: 11/12/2015
Citation: Prostko, E.P., Webster, T.M. 2015. Field corn response to diclosulam. Crop, Forage & Turfgrass Management. DOI:10.2134/cftm2015.0134.

Interpretive Summary: Diclosulam is a triazolopyrimidine sulfonanilide herbicide registered for use in peanut, controlling numerous weed species including several annual morningglories, eclipta, bristly starbur, and common ragweed. It is estimated that 25 to 30% of the peanut acreage in the southeastern US is treated annually with diclosulam. One limit to the potential use of diclosulam in peanut is corn rotation restrictions. The current labeled rotation restriction for field corn following an application of diclosulam is 540 days; the response of field corn to diclosulam residues has not been well documented. Therefore, research was conducted to determine the response of field corn to PRE applications of diclosulam with the intent of simulating carryover from applications made to a previous peanut crop. Diclosulam at 1 g ha-1 caused <12% corn injury and <3% plant stand or yield loss. A residual level of 1 g ha-1 of diclosulam in a field following application of a registered use rate of 27 g ha-1 would require approximately five half-lives. Thus, applying the longest reported half-life value (43 days) would render an estimated rotation restriction of 215 days. The current registration prohibits corn planting within 540 days after diclosulam application. However, it appears that this level of rotation restriction could be reduced for corn production in the coarse soils of the southeastern US, assuming typical rainfall patterns, supplemental irrigation programs, and normal temperatures occur.

Technical Abstract: Crop rotation restrictions often limit the use of diclosulam in peanut. Research was conducted in 2013 and 2014 to determine the response of field corn to PRE applications of diclosulam with the intent of simulating carryover from applications made to a previous peanut crop. Diclosulam was applied at 0, 1, 2, 3, 7, 13, 27, and 53 g ai ha-1 immediately after corn planting. The normal use rate of diclosulam is 27 g ha-1. Corn injury, stand loss, and yield loss increased with diclosulam rate. Diclosulam at 1 g ha-1 caused <12% corn injury and <3% plant stand or yield loss. These results suggest that field corn could be safely planted after a field dissipation rate of five half–lives. The reported half-life of diclosulam is 13 to 43 days. Thus, it is likely that the field corn rotation restriction could be reduced in the Southeast where corn is grown in warm climates on coarse-textured soils using supplemental irrigation which help contribute to optimum microbial degradation of herbicides.