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United States Department of Agriculture

Agricultural Research Service

Research Project: Adaptive Rangeland Management of Livestock Grazing, Disturbance, and Climatic Variation

Location: Livestock and Range Research Laboratory (LARRL)

Title: Aminopyrald and Picloram reduce seed production of the invasive annual grasses Medusahead and Ventenata

Authors
item Rinella, Matthew
item Bellows, Susan
item Roth, Aaron -

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2014
Publication Date: July 1, 2014
Citation: Rinella, M.J., Bellows, S.E., Roth, A.D. 2014. Aminopyrald and Picloram reduce seed production of the invasive annual grasses Medusahead and Ventenata. Rangeland Ecology and Management. 67:406-411.

Interpretive Summary: Invasive annual grasses are negatively impacting millions of acres of U.S. rangelands. Herbicides are sometimes used to control invasive annual grasses. We recently found that three herbicides currently not used for controlling invasive annual grasses (i.e. aminopyralid, dicamba, picloram) greatly reduced seed production in the invasive annual grasses downy brome and Japanese brome. The purpose of this greenhouse study was to extend this research to the invasive annual grasses medusahead and ventenata. We found that aminopyralid reduced medusahead seed production to nearly zero. Picloram also reduced medusahead seed production, but picloram responses varied appreciably by application timing, herbicide rate and experimental run. Aminopyralid applied at the seedling stage reduced ventenata seed production 95-99%. Beyond the seedling stage, however, ventenata responses to aminopyralid were highly variable. Picloram appears to have low activity against ventenata seed production. These results contribute to the growing body of evidence suggesting aminopyralid could be used to control a wide range of invasive annual grass species by depleting their short-lived soil seedbanks.

Technical Abstract: Invasive annual grasses are negatively impacting millions of hectares of U.S. rangelands. Sulfonylurea, amino acid synthesis inhibitor and photosynthesis inhibitor herbicides are sometimes used to control invasive annual grasses. On the other hand, growth regulator herbicides are widely used to control broadleaf weeds and are generally considered ineffective against invasive annual grasses. However, in a recent study the growth regulator herbicide aminopyralid applied pre-emergence reduced cover of the invasive annual grass medusahead (Taeniatherum caput-medusae (L.) Nevski). Also, we recently found that the growth regulators aminopyralid, dicamba and picloram applied at particular post-emergence growth stages caused plant sterility and thereby greatly reduced seed production in the invasive annual grasses downy brome (Bromus tectorum L.) and Japanese brome (Bromus japonicus Thunb. ex Murr.). The purpose of this greenhouse study was to extend our growth regulator/plant sterility research from downy brome and Japanese brome to medusahead and ventenata (Ventenata dubia (Leers) Coss.). We found that aminopyralid reduced medusahead seed production to nearly zero at each tested application growth stage (seedling, internode elongation, heading) and herbicide rate. Picloram also reduced medusahead seed production, but picloram responses varied appreciably by application timing, herbicide rate and experimental run. According to point estimates, aminopyralid applied at the seedling stage reduced ventenata seed production 95-99%. Beyond the seedling stage, however, ventenata responses to aminopyralid were highly variable. Picloram appears to have low activity against ventenata seed production. These results contribute to the growing body of evidence suggesting growth regulator herbicides, especially aminopyralid, could be used to control a wide range of invasive annual grass species by depleting their short-lived seedbanks.

Last Modified: 12/18/2014
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