Scattered rains have accumulated over the past week, with many receiving several inches or more. With even more rain in the forecast and many of our acres quickly entering their second and third week of bloom, the question of the week has been what to do with plant growth regulators. In contrast to previous years, the introduction of the active plinazolin (Vertento) has created a more interesting question- what can we do, from a plant growth regulator standpoint, to take full advantage of the long residual control window provided by this new product? In this blog, I outline the best approach to balance a possible opportunity to save an application cost with the risk of being too aggressive.
Dr. Sebe Brown covered plant bug management in depth last week (https://news.utcrops.com/2026/06/managing-plant-bugs-in-blooming-cotton-2/). Additionally, the MidSouth Cotton Specialists Working Group outlined the approach and structure to selecting rates in our new Plant Growth Regulation publication. I would encourage you to take a close look at the application table (Table 2). Given Tennessee’s season, many will find themselves in the 1-1.25 ounces per acre, per node application rate of a 4.2% product, as our season has generally been very good to great for supporting rapid vegetative growth. Still, this application structure may not be aggressive enough to adequately slow vegetative growth in our most aggressively growing acres for multiple weeks. In those acres, particularly if you have confidence that conditions to support excessive growth will continue, I would consider a 16 ounce application of a 4.2% mepiquat chloride product plus a 2 ounce application of Stance (containing both mepiquat chloride and cyclanilide). This very aggressive application will still keep us under the max single application rate limit for mepiquat chloride (24 ounces) and, in my opinion, represents our best shot at controlling growth.
One other note. Since Vertento is new, we have very limited data on tank mix partners. It is very likely that many will mix Vertento, a surfactant, mepiquat chloride, possibly mepiquat chloride + cyclanilide, a boron product, and maybe an herbicide. I would encourage you to proceed with caution as you add additional tank mix partners, test a small area for response before you treat the entire farm, and do not allow any concoction to sit in the tank for long periods of time before spraying. Unfortunately, although we do not expect any significant negative responses from the most common tank mixes, we have very limited tank mix comparability data with this new product.
