Are There Benefits to Applying PGRs to Cotton at or Near Cutout? (Collins, Edmisten, & Wells)
We’ve been getting a number of questions this week regarding the utility of mepiquat-containing PGRs applied to cotton at or near cutout. This idea has been around quite a while, and it has been suggested that PGRs applied at cutout could:
- enhance upper boll maturity by diverting photosynthetic resources away from young terminal leaves, or regrowth, and towards boll development,
- promote leaf maturity to simplify defoliation, or enhance harvest aid efficacy
- reduce regrowth and trash in harvested lint
- promote earlier maturity
- reduce ginning costs
- potentially higher yields and improved fiber quality
There has been a lot of discussion around this subject and these claims over the years, and many of the points above are even suggested on some PGR labels.
This concept has been thoroughly investigated in NC as well as in GA through a multi-year and multi-environment research project conducted a few years ago (which will likely be published soon). In this study, we evaluated many of the points above, including defoliation, percent open bolls and nodes above cracked boll as a measure of maturity, number of bolls and boll retention, desiccation, terminal and basal regrowth, yields, and fiber quality.
In this study, we found no meaningful benefit to applying PGRs to cotton that had reached cutout. There was no evidence to support that defoliation could be improved nor regrowth reduced to the point that defoliation strategies could be modified, and more importantly, there was no advantage to cutout application in terms of yield or quality. Earlier applications of PGRs (prebloom, early bloom, etc) continue to be recommended in some situations depending on many factors, however the potential benefit of PGRs appears to erode beyond mid-bloom. This study also suggested that there is little to no penalty from such late-season PGR applications, other than the added expense of products and application costs, especially if applied alone.