Abstract
Fifteen field trials were conducted from 2009 to 2011 in Ontario, Canada and Michigan, USA to determine how long glyphosate-resistant corn needs to be kept weed-free after emergence to prevent yield loss. Data were separated into two environments based on when yield loss first occurred after glyphosate application. In Environment 1 (4/15 sites) yield was not reduced when corn was kept weed-free until the 4-leaf stage. However, in Environment 2 (11/15 sites) there was no yield loss when corn was kept weed-free up to the 2-leaf stage. The most prominent weeds were velvetleaf, redroot pigweed, common ragweed, common lambsquarters and foxtail species. While later emerging weeds did not necessarily impact corn yield, weeds emerging after the 2- and 4-leaf corn stage likely produced seed that was added to the soil seed bank. Weeds emerging after 6-, 8-, and 10-leaf corn growth stages were small (low biomass/seedlings) and most likely did not reach reproductive maturity. Based on this research, corn must be maintained weed-free up to the 4-leaf stage. Any weeds emerging after that did not influence corn yield.
Highlights
Most of the corn produced in Canada is grown in Ontario where growers produce nearly 7.2 million tonnes of grain corn on approximately 822,000 hectares with a farm gate value of more than $1.3 billion [1,2]
Glyphosate-resistant corn is popular in Eastern Canada as it provides many benefits to growers including excellent crop tolerance, a wide window of herbicide application, broad spectrum weed control, more consistent weed control under various environments, lower cost of weed control, greater yield, and higher net returns [5]
Data were separated into two environments based on the impact of treatment on corn yield
Summary
Most of the corn produced in Canada is grown in Ontario (nearly 63%) where growers produce nearly 7.2 million tonnes of grain corn on approximately 822,000 hectares with a farm gate value of more than $1.3 billion [1,2]. Most of the corn grown in Ontario is glyphosate-resistant which has provided growers with additional weed management options with economic advantages [4,5]. In 2012, about 94% of the corn hectares in Eastern Canada were planted to glyphosate-resistant hybrids and the percentage is expected to increase in the future [4]. Glyphosate-resistant corn is popular in Eastern Canada as it provides many benefits to growers including excellent crop tolerance, a wide window of herbicide application, broad spectrum weed control, more consistent weed control under various environments, lower cost of weed control, greater yield, and higher net returns [5]. Growers often use one application of glyphosate applied early (EPOST) or late postemergence (LPOST) or a sequential application of glyphosate applied EPOST and LPOST as the primary weed management strategy to control troublesome weeds in glyphosate-resistant corn [6,7,8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
