Q: Has any work been done with controlling adzuki beans in IP, non-GMO soybeans?
A: Chris Kramer and colleagues at the University of Guelph evaluated management of volunteer adzuki beans (photo at top) during a period of four seasons. The main challenge with adzuki beans is that their pods shatter easily and their seed coat is hard and less permeable to water, which results in an increased longevity in the soil. In addition, the Kramer study found the peak germination of volunteer seed occurred mid- to late June and well into July (Figure 2 below), well past the appropriate application timing for many of the post-emergent herbicide options.
Unfortunately this study found no effective soil-applied herbicides and only one effective post-emergent herbicide, Classic + Agral 90 (Table 1 below). This information is also available in the pest manager app (click to see graphic) and the OMAFRA Guide to Weed Control for Field Crops (Figure 4 at bottom).
Summary: Volunteer adzuki beans in non-GMO soybeans can be controlled but only the post-emergent application of Classic + Agral 90 has provided acceptable results. Ultimately, doing your best to minimize harvest losses will be an important strategy to reduce the amount of volunteer seedlings that you’ll have to control the following season. Future studies should evaluate the impact that fall and spring tillage have on seedling mortality.