Prosopis velutina response to aerial herbicide application

Authors: ARCHER, S.R. - University Of Arizona; NAITO, A.T. - Northern Michigan University; Heilman, Philip - Phil; VIVONI, E.R. - Arizona State University; Scott, Russell - Russ

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2023
Publication Date: 4/8/2023
Citation: Archer, S., Naito, A., Heilman, P., Vivoni, E., Scott, R.L. 2023. Prosopis velutina response to aerial herbicide application. Rangeland Ecology and Management. 88:129-134. https://doi.org/10.1016/j.rama.2023.02.014.
DOI: https://doi.org/10.1016/j.rama.2023.02.014

Interpretive Summary: We documented the impacts of a commonly used herbicide cocktail on velvet mesquite in Sonoran Desert grasslands in southern Arizona. Like other concurrent applications of comparable herbicide cocktail formulations in the region, we recorded only modest and short-term impacts. Velvet mesquite mortality was only 7%. Foliar cover declined to 16.3 ± 1.45 % the month following treatment, was comparable across size-classes and persisted for about 2 years, by which time it was comparable on treated and control plants (67.8% and 67.5%, respectively). Based on eddy covariance data monitoring gross primary productivity, precipitation, evapotranspiration, soil temperature, and soil moisture, we propose that knowledge of soil moisture and photosynthetic activity may help identify optimal times to apply herbicides to improve herbicide efficacy, which have previously been based on recommendations for honey mesquite in Texas and New Mexico. Future research should explore velvet mesquite response to herbicides at various levels of photosynthetic activity in response to soil temperature and soil moisture in Sonoran Desert and transition zone between the Chihuahuan and Sonoran Deserts. From a broader ecosystems trophic perspective, our results also suggest a need to learn how herbicide-induced reductions in velvet mesquite pod and seed production may impact native herbivore communities.

Technical Abstract: We documented the impacts of a commonly used herbicide cocktail on Prosopis velutina in Sonoran Desert grasslands in southern Arizona. Similar to other concurrent applications of comparable herbicide cocktail formulations in the region, we recorded only modest and short-term impacts. P. velutina mortality was 7%. Foliar cover declined to 16.3 ± 1.45 % the month following treatment, was comparable across size-classes and persisted for ~ 2 years, by which time it was comparable on treated and control plants (67.8% and 67.5%, respectively). Based on eddy covariance data monitoring gross primary productivity, precipitation, evapotranspiration, soil temperature, and soil moisture, we propose that knowledge of soil moisture and photosynthetic activity may help identify optimal times to apply herbicides to improve herbicide efficacy. Future research should explore P. velutina response to herbicides at various levels of photosynthetic activity in response to soil temperature and soil moisture in the subtropical North American Monsoon climate system of the Sonoran Desert. From a broader ecosystems trophic perspective, our results also suggest a need to ascertain how herbicide-induced reductions in P. velutina pod and seed production may impact native herbivore communities.