A spring of extremes — first cold, dry and windy, then hot, dry and windy — has resulted in weeds getting a head start in many soybean fields in the soybean-growing areas of Western Canada.

While wind and cold temperatures delayed burnoff applications at the start of the season, questions about when to spray in extreme, hot conditions have become common with the arrival of a major heat wave over the last week.

“The heat of the day is challenging, as if you’re up over 28 degrees you can get additional crop injury and plants start to shut down,” explains Harold Brown, technical service specialist with BASF in eastern Manitoba, in this weed control-themed Soybean School episode.

From a temperature perspective, early morning and late evening are usually more ideal than the heat of the day. But when we’re talking about managing hard-to-control weeds in soybeans, such as glyphosate-resistant kochia, the conversation often involves dicamba, and dicamba is at risk of drift due to inversions.

“We’re saying don’t spray in the heat of the day, so maybe in the cooler parts of the evening or early morning, although you can have some challenges with inversions, so there’s not a simple answer,” notes Brown. “Maybe the best thing is to delay spraying if the weeds are really small until after this hot weather has gone by.”

Brown discusses the process of deciding when to spray amidst challenging weather with oncoming weeds, crop staging, and more in this Soybean School episode:

Leave a Reply


This site uses Akismet to reduce spam. Learn how your comment data is processed.

Privacy Preference Center


Necessary cookies help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these cookies.

gdpr, __cfduid, PHPSESSID, wordpress_test_cookie, woocommerce_items_in_cart, woocommerce_cart_hash, wp_woocommerce_session, wordpress_logged_in, wordpress_sec, wp-settings, wp-settings-time, __cf_mob_redir, wordpress_cache, realag


Measuring interactions with the ads on the domain.



These are used to track user interaction and detect potential problems. These help us improve our services by providing analytical data on how users use this site.



Preference cookies enable the website to remember information that changes the way the website behaves or looks, like your preferred language or the region that you are in.

chartdefaults, comment_author, comment_author_email, comment_author_url
JSESSIONID, _os_session,anonymous_votes,csrf-param,csrf-token,user,user-id,user-platform,intercom-session,intercom-lou,intercom-session
personalization_id, tfw_exp