Is volunteer wheat an economic weed in annual winter wheat production?

Authors: Wuest, Stewart; BARROSO, JUDIT - Oregon State University; GENNA, NICHOLAS - Oregon State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2020
Publication Date: 1/5/2021
Citation: Wuest, S.B., Barroso, J., Genna, N.G. 2021. Is volunteer wheat an economic weed in annual winter wheat production? Agronomy Journal. 113(2):1724-1732. https://doi.org/10.1002/agj2.20591.
DOI: https://doi.org/10.1002/agj2.20591

Interpretive Summary: When volunteer wheat infests a crop of a different species it is clearly a weed. How should we view volunteer wheat growing in a subsequent wheat field, since it can potentially add to yield? Our objective was to evaluate the effect of volunteer wheat on the yield of wheat grown in the same field every year in wheat monoculture. Data was collected in 2015 and 2016 in three fields of the inland Pacific Northwest, USA. Average volunteer head densities were between 13% and 28% of total heads, with a high of 66% found in chaff rows. Volunteer wheat produced between 8% and 19% of total yield. Total yield was reduced by the presence of volunteer. At 120 volunteer wheat heads m-2 (approximately 30 plants m-2) the estimated yield loss was 11.6%. In addition to yield loss, there are other problems that volunteer can cause such as dockage if the wheat varieties are different market classes, passing on herbicide resistance traits, or increasing pests or diseases in the seeded wheat. Considering these concerns, practices should be implemented to minimize volunteer wheat in winter wheat fields.

Technical Abstract: Annual winter grasses are competitive weeds in winter wheat (Triticum aestivum) due to their similar life cycle, root system, and morphology. Volunteer wheat is clearly a weed when infesting a crop of a different species. However, should substantial expense be invested in reducing volunteer wheat in a subsequent wheat crop? The effects of volunteer wheat in winter wheat were investigated in three fields of the inland Pacific Northwest, USA during 2015 and 2016. Volunteer wheat was found evenly distributed in fields harvested with a commercial combine with a chaff spreader. The ratio of volunteer to seeded wheat density was constant even in high productivity areas that had higher wheat densities. Volunteer head densities ranged from 13% to 28% of total heads with a high of 66% found in chaff rows. Volunteer wheat produced between 8% and 19% of total yield. The productivity per head of seeded wheat was higher than volunteer wheat and volunteer wheat reduced seeded wheat yield in all fields. The estimated total yield loss across fields was 10.8%. Volunteer wheat may cause less yield loss than other winter annual weeds because of its contribution to yield. However, a 10% yield loss is significant and practices to minimize volunteer wheat in wheat fields are recommended.