Herbicide Applications During Dry, Hot Months

Posted on May 27, 2022 by vanessa.corriher

Invasive brush can decrease forage productivity for livestock or decrease brush diversity valuable for wildlife habitat. Most ranchers find themselves constantly considering options for brush management, weighing not only the cost and effectiveness, but also when they can find the time to complete the treatments. As temperatures continue to climb across the state and the chances of rainfall seem to be weakening, it’s important to consider the effect this will have on any herbicide applications.Treating weeds or brush with a leaf spray application when temperatures are as high as they have been lately will usually result in poor control for several reasons. Plants likely have slowed down their growth and will not move the herbicide down to the roots to control the plant as readily during this time. Additionally, insect damage during this time of year also decreases the amount of leaf available to take in the herbicide. Finally, hot temperatures make leaves waxier; a trait used by plants to retain moisture, but will decrease the herbicides’ ability to get into the leaf. The next leaf spray season will be this fall (October) when it is recommended to treat plants such as huisache, Macartney rose, and Chinese tallowtree.

If you find yourself willing to brave the heat, what herbicide applications could you do during these hot months? Stem spray applications and cut-stump treatments may be done most any time during the year. Stem sprays involve spraying each stem of a brush plant, all the way around, about 12-18” high. This treatment is best on trees with three or less stems because more stems increases the opportunity to miss one of those buds underneath the ground and allow the plant to regrow! The mix for the stem spray method is simple: 25% triclopyr (such as Remedy Ultra) and 75% diesel. This should be applied in a straight stream directed right onto the stem. Plants must be left alone for one full year before removing the ‘skeleton’ or burning the pasture.

An alternative treatment is the cut-stump method. While this method requires more labor upfront, it is essential 100% effective if done correctly! The tree should be removed as low and flat as possible without any dirt or saw dust left on the remaining cut surface. This could be done with a shear, chainsaw, loppers, or a brush cutter (weedeater with a brush cutter attachment). A mixture of 15% triclopyr (such as Remedy Ultra) and 85% diesel will be applied onto the entire cut surface and any remaining stem. This treatment can be done any time of year, so keep in mind that December may provide more favorable weather for those doing the cutting!

When spraying with high temperatures, time your applications for early in the morning when temperatures are not as high. Never spray when temperatures exceed 90 degrees. Some herbicides (such as Remedy Ultra) are especially susceptible to volatilization, so care should be taken to protect desirable plants from accidental movement of the herbicide. Be sure to drink lots of water and take frequent breaks. No huisache tree is worth risking your health!

Megan K. Clayton, Ph.D.

Extension Range Specialist, Texas A&M AgriLife Extension Service