Searching for consistent postemergence weed control in progressively inconsistent weather

Authors: Landau, Christopher; BRADLEY, KEVIN - University Of Missouri; BURNS, ERIN - Michigan State University; DOBBELS, ANTHONY - The Ohio State University; ESSMAN, ALYSSA - The Ohio State University; FLESSNER, MICHAEL - Virginia Tech; GAGE, KARLA - Southern Illinois University; HAGER, AARON - University Of Illinois; JHALA, AMIT - University Of Nebraska; JOHNSON, PAUL - South Dakota State University; JOHNSON, WILLIAM - Purdue University; LANCASTER, SARAH - Kansas State University; LINGENFELTER, DWIGHT - Pennsylvania State University; LOUX, MARK - The Ohio State University; MILLER, ERIC - Southern Illinois University; OWEN, MICHAEL - Iowa State University; SARANGI, DEBLIN - University Of Minnesota; SIKKEMA, PETER - University Of Guelph; SPRAGUE, CHRISTY - Michigan State University; VANGESSEL, MARK - University Of Delaware; WERLE, RODRIGO - University Of Wisconsin; YOUNG, BRIAN - Purdue University; Williams, Martin

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2024
Publication Date: 11/18/2024
Citation: Landau, C.A., Bradley, K., Burns, E., Dobbels, A., Essman, A., Flessner, M., Gage, K., Hager, A., Jhala, A., Johnson, P., Johnson, W., Lancaster, S., Lingenfelter, D., Loux, M., Miller, E., Owen, M., Sarangi, D., Sikkema, P., Sprague, C., Vangessel, M., Werle, R., Young, B., Williams, M. 2024. Searching for consistent postemergence weed control in progressively inconsistent weather. Weed Science. https://doi.org/10.1017/wsc.2024.80.
DOI: https://doi.org/10.1017/wsc.2024.80

Interpretive Summary: Over the next century, major corn and soybean growing regions of North America are expected to experience a changing climate manifested as greater frequency of extreme weather events. How might climate change affect performance of herbicides applied postemergence (POST) for weed control in corn and soybean? We analyzed university-led POST trials from across thousands of environments and found that average air temperature 10 days after POST application was the most important predictor of successful weed control, with weed control deteriorating rapidly above certain thresholds. Additionally, precipitation 10 days before and after POST application were important predictors in some cases, although the direction (positive or negative effect) varied by weed species and herbicide. As air temperatures increase and precipitation becomes more variable for most of North America, the risk of poor weed control with these common POST herbicides will increase.

Technical Abstract: Foliar applied postemergence (POST) herbicides remain a critical component of corn and soybean weed management programs in North America. Rainfall and temperature around the time of application may affect the efficacy of some of the common herbicides applied to corn or soybean and this effect is often species dependent. However, previous research utilizes a limited number of site-years which may not accurately capture the full range of rainfall and air temperature that these herbicides are exposed to throughout North America. The objective was to model the probability of achieving successful weed control (=85%) with common foliar-applied POST herbicides across a broad range of environments. A large database of over 10,000 individual herbicide evaluation trials conducted throughout North America was used. The database was filtered to include only trials with a single POST application of fomesafen, glyphosate, mesotrione, or fomesafen + glyphosate. Waterhemp (Amaranthus tuburculatus (Moq.) J. D. Sauer), morningglory species (Ipomoea spp.), and giant foxtail (Setaria faberi Herm.) were the focus of this study and separate random forest models were created for each weed species by herbicide combination. The probability of successful weed control plummeted when daily average temperatures were >25°C or <19°C for most of the herbicide by weed species models. Additionally, dry conditions prior to POST application reduced the probability of control for several models. As temperatures increase and rainfall becomes more variable throughout much of North America, weed control with many of the commonly used POST herbicides is likely to become more unreliable and inconsistent.