Envu’s Dr Case Medlin Presents Findings at The International Rangeland Congress in Adelaide

Last week, Dr Case Medlin, Regional Solution Development & Technical Services Manager from the Envu  U.S team presented at the 12th International Rangeland Congress  in Adelaide from 2-6 June. The congress, which is held every 3-5 years, aims to promote the interchange of scientific and technical information on all aspects of rangelands by bringing together individuals working in rangelandcommunities from all over the world.

On Day 2 of the congress, Dr Case shared his expertise on the long-term chemical management of undesirable brush on U.S. rangelands—a topic highly relevant for landholders working to reclaim rangelands across both the U.S. and Australia.

His work highlights the importance of evaluating success beyond short-term control. As Case put it:

“Building broad-spectrum control recommendations for rangeland restoration with ACP as the foundation is offering landholders a long-term solution to invasive woody species that have plagued their land for generations.”

In his presentation, he also shares findings which support flexible, goal-based herbicide strategies for landowners aiming to manage invasive brush species while maintaining desirable plant diversity.

Below is an abstract from his presentation:

Abstract 

Woody plant encroachment on rangeland used for beef cattle production and/or wildlife use in the southwestern United States has been a major problem of ranchers for many decades.  Aminocyclopyrachlor  premixed with  triclopyr-amine was first marketed for use on grazing lands in Texas, Oklahoma, New Mexico, and Arizona in 2020. This herbicide was marketed for control of honey mesquite (Prosopis glandulosa) (NRCS 2025), huisache (Vachellia farnesiana a.k.a. Acacia farnesiana), and associated brush species and broadleaf forbs on grazing lands. Long-term (i.e. four to ten years post-application) honey mesquite canopy evaluations in aerial and ground broadcast-applied trials revealed more than twice the treatment life (i.e. the time from treatment until brush canopy returns to an economic threshold) with aminocyclopyrachlor+triclopyr-amine  (ACP+T) treated plots versus plots treated with past industry standards (Medlin et al. 2019). Similar results were obtained for huisache treated plots evaluated four to six years post-application. Recent research has evaluated picloram and/or  chlorsulfuron+metsulfuronmethyl  combinations applied with ACP+T to widen the spectrum of activity and address additional  undesirable species on rangelands while evaluating impacts on desirable plant species. When evaluated 40 months after application, ACP+T (140+280 g ae ha^-1 )  applied alone was highly efficacious (100% mortality) on honey mesquite, moderately efficacious (66% mortality) on guajillo  (Acacia berlandieri), and slightly efficacious (less than 25% mortality) on all other woody plant species present. When ACP+T was applied in combination with picloram (560 g ae ha^-1 )  or picloram and chlorsulfuron+metsulfuron-methyl  (10.5+33.5 g ai ha^-1 )  mortality of twisted acacia (Vachellia schaffneri  a.k.a. Acacia schaffneri) increased to 25% and 50%, respectively. 

A tank mix of ACP+T (210+420 g ha^-1 ) with chlorsulfuron+metsulfuron-methyl resulted in 100% mortality of honey mesquite, twisted acacia, and whitebrush (Aloysia gratissima), less than 25% mortality of spiny hackberry  (Celtis ehrenbergiana), and 0% mortality of ephedra (Ephedra antisyphilitica), guayacan (Guaiacum angustifolium), and lotebush  (Ziziphus obtusifolia).

You can find his full presentation in the conference proceedings (Paper #507):
View Proceedings

Some of Case’s additional findings are also featured in Weed Technology:
Read the Article

Sources:

https://irc2025.rangelandcongress.org/wp-content/uploads/2022/12/XII-IRC-Proceedings-Draft-com-compressed.pdf