Sponsored By
Kansas Farmer Logo

4 things to note when applying herbicides in high heat4 things to note when applying herbicides in high heat

Manage your applications so your product works effectively, even in spiked temperatures.

Jennifer M. Latzke

June 29, 2023

2 Min Read
Tractor applying herbicide in field
HERBICIDE APPLICATION: As temperatures start to heat up through the end of June, farmers need to remember four key tips when they’re applying herbicides during high heat, advises Sarah Lancaster, Kansas State University Extension weed science specialist. Courtesy of K-State Extension News Service

Farmers should be prepared for temperatures to heat up through the last part of June. That means they need to pay special attention to their herbicide applications in high heat conditions, explains Sarah Lancaster, Kansas State University Extension weed science specialist.

Lancaster wrote about four herbicide application management tips in the June 15 Agronomy eUpdate.

  1. Heat or drought stress slows the plant growth processes.  As temperatures climb above 85 degrees F, she writes, plants being to slow or stop their metabolic processes, which move herbicides through the plant. If you’re applying systemic herbicides (glyphosate, Select or Assure) do so early in the morning, after the plants have a chance to recover from the heat stress of the day prior. And remember, if you’re applying HPPD-inhibiting herbicides (Callisto or Balance Flexx), just know that palmer amaranth plants can overcome these herbicides when applied at temperatures of 90 degrees or warmer.

  2. Leaves change in response to heat. Remember, the plant’s defense mechanisms against heat are its cuticles, which become waxier to prevent water loss from its leaves. Some plants may change their leaf angles in response as well. To bypass these defenses, Lancaster recommends using the maximum labeled rates of herbicides and surfactants to get more spray solution into the plant. And spray during the cooler part of the day to reach the leaves at their peak angle.

  3. Don’t forget: Your crops react to heat as well. The same heat that affects weeds in the field causes crop responses as well. If you’re applying foliar, non-translocated herbicide, in hot and humid conditions, those contact herbicides (Cobra, Liberty or Reflex) will likely result in greater foliar injury to your crops — as well as greater weed control. Lancaster recommends postponing applications if temperatures are over 90 degrees. But if you can’t postpone due to the size of the weeds in the field you’re trying to control, she recommends reducing your rate of herbicide and adjuvant, and apply later in the day when the air temperature will cool after your application.

  4. Herbicide volatility increases with higher temperatures and low humidity. Group 4 herbicides (dicamba, 2,4-D) are prone to volatility at temperatures as low as 60 degrees, and their volatility is greatest at temperatures above 90 degrees. To reduce the chance of your product vaporizing and moving with the breeze onto unintended targets, Lancaster recommends avoiding application of these herbicides when temperatures are over 90 degrees — and especially during morning or late afternoon hours, when temperature inversions are more likely to occur. Inversions, she reminds farmers, can trap small spray droplets in a layer of cool air near the Earth’s surface. To combat this, she advises using larger spray droplets to reduce the likelihood of evaporation.

As always, Lancaster reminds growers to always consult the herbicide label for the most current use requirements. To learn more, read the June 15 Agronomy eUpdate or contact your local K-State Extension office.

The Kansas State Department of Agronomy contributed to this article.

About the Author(s)

Jennifer M. Latzke

Editor, Kansas Farmer

Through all her travels, Jennifer M. Latzke knows that there is no place like Kansas.

Jennifer grew up on her family’s multigenerational registered Angus seedstock ranch and diversified farm just north of Woodbine, Kan., about 30 minutes south of Junction City on the edge of the Kansas Flint Hills. Rock Springs Ranch State 4-H Center was in her family’s backyard.

While at Kansas State University, Jennifer was a member of the Sigma Kappa Sorority and a national officer for the Agricultural Communicators of Tomorrow. She graduated in May 2000 with a bachelor’s degree in agricultural communications and a minor in animal science. In August 2000 Jennifer started her 20-year agricultural writing career in Dodge City, Kan., on the far southwest corner of the state.

She’s traveled across the U.S. writing on wheat, sorghum, corn, cotton, dairy and beef stories as well as breaking news and policy at the local, state and national levels. Latzke has traveled across Mexico and South America with the U.S. Wheat Associates and toured Vietnam as a member of KARL Class X. She’s traveled to Argentina as one of 10 IFAJ-Alltech Young Leaders in Agricultural Journalism. And she was part of a delegation of AAEA: The Ag Communicators Network members invited to Cuba.

Jennifer’s an award-winning writer, columnist, and podcaster, recognized by the Kansas Professional Communicators, Kansas Press Association, the National Federation of Presswomen, Livestock Publications Council, and AAEA. In 2019, Jennifer reached the pinnacle of achievements, earning the title of “Writer of Merit” from AAEA.

Trips and accolades are lovely, but Jennifer says she is happiest on the road talking to farmers and ranchers and gathering stories and photos to share with readers.

“It’s an honor and a great responsibility to be able to tell someone’s story and bring them recognition for their work on the land,” Jennifer says. “But my role is also evolving to help our more urban neighbors understand the issues our Kansas farmers face in bringing the food and fiber to their store shelves.”

She spends her time gardening, crafting, watching K-State football, and cheering on her nephews and niece in their 4-H projects. She can be found on Twitter at @Latzke.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like