Battle for the Belt: Season 3, Episode 17: Residual Herbicides

Season 3, Episode 17 of Battle for the Belt is now available: https://youtu.be/RPxbQnXZ_zE

In Episode 17, we talked with Colin Barclay, Weed Science Research Associate under Dr. Alyssa Essman, Ohio State Extension Weed Specialist. We discussed the potential benefit of including a residual herbicide application at your post-emergence herbicide application timing.

Colin is working on a study in collaboration with the University of Wisconsin. In this soybean study, Group 2 (ALS inhibitor) and Group 14 (PPO inhibitor) herbicides were applied at pre-emergence. At post-emergence, various treatments were applied using a Group 15 (long-chain fatty acid inhibitor) herbicide. Some plots received no residual at the post-application, allowing for the observation of a second flush of waterhemp in those treatments.

This observation is likely to reflect what growers across Ohio are seeing- waterhemp pressure is rising, and post-emergence applications without a residual allow escapes. A two-pass post program can be beneficial, with the residual being applied at the earlier of the posts. This minimizes crop injury and extends control through soybean canopy closure.

Waterhemp is the weed of focus in this trial. However, other weed species are being monitored, such as giant ragweed, which tends to be present in western Ohio. Similar to that of waterhemp, with the inclusion of a residual, there is reduced pressure of giant ragweed, with fewer plants emerging or smaller populations overall.

The key message from this week’s episode? A strong herbicide program using multiple effective sites of action, including residuals, is critical. “Start clean, stay clean.”

Field & Crop Progress Updates

Wooster is leading the way in soybean growth progression, reaching the fourth reproductive stage, R4 (full pod) in planting date one (3/27) last week. The R4 growth stage is characterized by the presence of a pod, at least ¾ of an inch long (Figure 1), at one of the four uppermost nodes on the main stem with a fully developed leaf. The number of pods per acre determines the maximum number of seeds per acre, making pod development a highly important period for soybean production. Scouting fields is a key task to complete at the R3-R4 stage. If diseases, insects, or nutrient deficiencies are present, pesticide or nutrient applications are something to consider if conditions warrant and thresholds for treatment have been met.

Soybeans from planting dates one through three have reached reproductive stages at all three locations. Corn at the Wooster location has reached the silking growth stage (R1) in the first planting date. This leaves the Northwest location as the last to transition from the vegetative to the reproductive growth stages for planting date one in corn. Growth stages for all planting dates and locations are summarized in Table 1 for reference

Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.