Volunteer rapeseed infestation and management in corn

Authors: KUMAR, VIPIN - Virginia Tech; SING, VIJAY - Virginia Tech; FLESSNER, MICHAEL - Virginia Tech; REITER, MARK - Virginia Tech; Mirsky, Steven

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2023
Publication Date: 9/22/2023
Citation: Kumar, V., Sing, V., Flessner, M., Reiter, M., Mirsky, S.B. 2023. Volunteer rapeseed infestation and management in corn. Agronomy Journal.115:2925–2937 https://doi.org/10.1002/agj2.21476.
DOI: https://doi.org/10.1002/agj2.21476

Interpretive Summary: The more biomass (i.e. plant matter) a cover crop generates, the more benefits it typically provides. However, in the case of rapeseed, allowing the cover crop to grow until maximum biomass risks the production of seed that can volunteer (become weeds) in a following cash crop. In this study, the rapeseed was terminated at different times to evaluate the effect on biomass production, termination efficiency, volunteers in a following corn crop, and herbicide control of volunteer rapeseed. Delayed rapeseed termination led to increased biomass, decreased termination efficiency, and increased number of volunteer seedlings. However, since the risk of volunteers was related more to termination efficiency than biomass production, successfully terminating the cover crop decreased the number of volunteers. This study also identified which herbicides are best for terminating volunteer seedlings, providing concrete guidance as to best management practices crucial to the successful use of cover crops. This work will support farmers in their decision making on cover crop management.

Technical Abstract: Termination at maximum biomass is desired for harnessing the benefits of cover crops but delayed rapeseed termination causes a risk of volunteer rapeseed infestation in successive cash crops due to its pod-shattering properties. The study was conducted to evaluate the effect of different termination timings for rapeseed on biomass production, termination efficiency, and volunteer rapeseed infestation in the successive cash crop (corn), and control of volunteer rapeseed with herbicides. Delaying the termination from 28 days before planting corn (DBP) to 14, 5, or 1 DBP, increased rapeseed biomass by 85, 148, and 158%, respectively. Rapeseed termination efficiency was greatest 28 DBP (99%) followed by 14 DBP (92%) and 5 DBP (89%) with the combined use of a roller-crimper and 2,4-D (540 g ae ha-1) + glufosinate (656 g ai ha-1). Whereas, sole use of roller-crimper 1 DBP provided only 56% termination. Zero volunteer rapeseed plants were observed in the successive cash crop with 28 DBP termination treatment, however, 14 DBP resulted in 5 volunteer rapeseed plants m-2, followed by 12 and 22 plants m-2 at 5 and 1 DBP. Regression analysis showed that variation in volunteer rapeseed density can be better explained by termination efficiency (R2 = 0.80) as compared to rapeseed biomass at termination (R2 = 0.46), indicating that risk of volunteer rapeseed can be reduced with effective termination. Among pre-emergence (PRE) herbicides, mesotrione, rimsulfuron, and flumioxazin provided more than 95% volunteer rapeseed control 28 days after herbicide application (DAA), whereas control 28 DAA was 92-94% for atrazine, isoxaflutole, metribuzin, and pyroxasulfone. Among post-emergence (POST) herbicides, atrazine and glyphosate provided 99% control of rapeseed 28 DAA, followed by glufosinate (89%). Results from this study indicate that delaying the termination of rapeseed cover crop can result in volunteer rapeseed infestation in successive cash crops, which can be efficiently controlled by PRE and POST-herbicides.