Cotton is moving along as many of us county agents were at the National Association of County Agents meeting last week in Chattanooga. It was raining up there about as much as it was here. This can cause an issue with our PGR applications as the mepiquat chloride products have 8 hrs. Generally, when a surfactant is used, we can cut the rainfast in half. Pentia is more expensive, but with a 2 hour rainfast (1 hr with surfactant), it may help us when it’s wet.
Here is information from UGA Extension Cotton Agronomist Mark Freeman on terminating PGR applications:
When should we terminate our PGR applications? Research conducted at UGA and other parts of the country suggest that PGR applications should cease when cotton reaches 5 nodes above white flower. In theory a late season mepiquat application could stop further vegetative growth and divert carbohydrates and resources to boll production, but research has shown that there is no benefit to cotton yields, plant heights, fiber quality, or regrowth potential after defoliation.
One more note on PGRs, with the widespread rain across the state, the issue of rainfastness has been a concern when applying mepiquat. The rain free period after mepiquat chloride application is 8 hours. Although tank mixtures with an adjuvant are not necessary, their use may aid in plant uptake and help shorten that rain free window. Another option is Pentia (mepiquat pentaborate). Pentia requires a rain free period of two hours after application and that can be reduced to one hour when Pentia is tank mixed with an adjuvant.