Is volunteer wheat a serious weed in annual winter wheat production?

Annual winter grasses are the most competitive weeds in annual winter wheat production because their life cycle, root system, and morphology are more similar to the crop than the broadleaf weeds. Volunteer wheat growing in a crop of a different species has been identified as a weed. However, the effect of volunteer crops when they can add to the yield of the subsequent crop is more uncertain. The objective of this research was to evaluate the effect of volunteer wheat in wheat monoculture. Two different experiments were conducted in 2015 and 2016 in three fields of the inland Pacific Northwest (PNW) region (USA). Results showed average volunteer wheat densities between 13% and 28% in the wheat fields, although 61% was found in chaff rows. Volunteer wheat produced between 8% and 19% of the total yield. Despite the volunteer and seeded wheat both being high yielding varieties, the productivity per head of seeded wheat was higher than volunteer wheat for all the fields. The volunteer wheat behaved as a weed because the yield from the seeded wheat decreased when volunteer head density increased for all fields. When total wheat yield was considered (seeded plus volunteer), the estimated yield loss at 120 volunteer wheat heads m-2 (approx. 30 plants m-2) was 10%. In addition to the demonstrated yield loss, there are other problems that volunteer can cause such as dockage if the wheat varieties come from different market classes, passing on herbicide resistance traits, or increasing pests or diseases in the seeded wheat. Considering all these concerns, several practices should be considered in order to minimize the density of volunteer wheat in a winter wheat field