Defoliation Strip Trial Overview, Insight To Performance In Cool Conditions
DR. TYSON RAPER
JACKSON, TENN.
On September 18th, we applied a defoliation strip trial in Gift, Tenn. The field was 85 percent open with juvenile and mature leaves present. As you likely recall, this was immediately before a cold snap. Night temperatures for the next five days were 54, 55, 55, 59 and 57. In this blog, I describe the concoctions applied, share a brief video of the results 13 days after the initial application, and highlight a few important take-homes from the video.
The first few treatments were concocted to give you insight into plant response to individual products. The remaining treatments are common concoctions for West Tennessee. Treatments were 4 rows wide, with an orange stake visible in row 1 on the left of each treatment. While the video provides some insight into response, very noticeable differences were evident when walking the trial. My ratings on % leaves which were stuck, % juvenile leaves remaining on the plant, and % mature leaves remaining on the plant are included in the table.
Points of interest:
1. Thidiazuron activity drops exponentially to almost no activity when night temps fall to 55F. Click here to see a closeup of treatment 1.
2. A significant increase in leaf shed was noted when boll opener is included, regardless of product. Even if you don’t need much boll opening, some ethephon should be included. This is an important point for those applying a second shot to remove juvenile growth or a skirt, even when almost all bolls are open.
3. Including an ounce of diuron resulted in the greatest level of stuck leaves. Almost 30 percent of all leaves present on the plant stuck.
4. In cool conditions, treatment 9 (Folex @ 7oz plus Prep @ 32oz) resulted in the greatest levels of leaf shed and the lowest level of stuck leaves. Treatment 14 (Folex @ 12oz plus Prep @ 32oz) represented a mix that was too hot, but still didn’t generate the leaf stick noted in treatment 13.
Thidiazuron + diuron products may find a home in the first shot after temps climb into the mid-50s, but for now they are not in my mixes. Moving into next week my first shot will consist of Folex (7-10 oz) plus boll opener (16-32 oz) with a plan to follow with a second shot (PPO + boll opener). ∆
DR. TYSON RAPER: Cotton & Small Grains Specialist, University of Tennessee
