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Time of Day Impacts Postemergence Weed Control in Corn

Published online by Cambridge University Press:  20 January 2017

Christie L. Stewart
Affiliation:
Department of Biological Sciences, University of Western Ontario, London, ON N6A 3K7
Robert E. Nurse*
Affiliation:
Agriculture and Agri-Food Canada, 2585 County Rd. 20 R.R. #2 Harrow, ON N0R 1G0, Canada
Peter H. Sikkema
Affiliation:
University of Guelph Ridgetown Campus, Ridgetown, ON N0P 2C0, Canada
*
Corresponding author's E-mail: nurser@agr.gc.ca.

Abstract

Field trials were conducted from 2005 to 2007 at two locations in southwestern Ontario to investigate how weed control in corn was affected by the time of day that herbicides were applied. Weed control following the application of six POST herbicides (atrazine, bromoxynil, dicamba/diflufenzopyr, glyphosate, glufosinate, and nicosulfuron) at 06:00, 09:00, 12:00, 15:00, 18:00, 21:00, and 24:00 h was assessed. For many weed species herbicide efficacy was reduced when applications were made at 06:00, 21:00, and 24:00 h. Velvetleaf was the most sensitive to the time of day effect, followed by common ragweed, common lambsquarters, and redroot pigweed. Annual grasses were not as sensitive to application timing; however, control of barnyardgrass and green foxtail was reduced in some environments at 06:00 h and after 21:00 h. Only in the most severe cases was the grain yield of corn reduced due to decreased weed control. Daily changes in air temperature, relative humidity, and light intensity that cause species-specific physiological changes may account for the variation in weed control throughout the day. The results of this research suggest that there is a strong species-specific influence of ambient air temperature, light intensity, and leaf orientation on the efficacy of POST herbicides. These results should aid growers in applying herbicides when they are most efficacious, thus reducing costs associated with reduced efficacy.

Information

Type
Weed Management—Major Crops
Copyright
Copyright © Weed Science Society of America 

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