By Bill Robertson, Extension Cotton Agronomist
The Horse is Eyeing the Gate!
When planting conditions finally became favorable the last few days of April, they stayed that way. One of the television weather persons from Little Rock indicated that the high temperatures every day in May had exceeded the average for that date. Our cotton has come up quickly where it was planted into moisture and has experienced little stress to slow growth. The National Agricultural Statistics Service (NASS) Crop Progress and Condition Report for Arkansas the week ending May 27 reported cotton emergence at 85% which was ahead of the five-year average of 74%. They also reported that 89% of the cotton was in good (59%) to excellent (30%) condition with only 10% being fair, 1% poor, and none rated very poor. The NASS acreage intentions released March 29 were at 480,000 acres, up 8 percent from the 445,000 acres planted last year. It was estimated by some that planted acres could approach or break the 500,000 acre mark. The Arkansas Boll Weevil Eradication Foundation is wrapping up their mapping of the 2018 crop and feel that we will be short of the 500,000 mark, likely more in line with the NASS estimates.
We have planted varieties with a fairly wide range of growth habits. Plant population has a great influence on the expression of a varieties potential to become rank. Generally our best cotton crops are seen in years in which plant height is about belt high. Our population is set and we must rely on other strategies and practices to help keep vegetative growth in check. Maintaining a good fruit load and proper management of nitrogen and irrigation can go a long ways to keep the balance of vegetative and reproductive growth where we want it. The use of growth inhibiting plant growth regulators (PGR) is a widely use tool to supplement other practices to manage cotton. Growth inhibiting PGR products such as mepiquat chloride should be well-timed in anticipation of excessive growth rates to more effectively manage vegetative growth and plant height. Common timings to begin the use of these products is pinhead (PHS) to match head (MHS) square. These products work as a result of the concentration of the PGR in the plant which goes to reason that it is much easier to obtain and maintain the desired concentration in a plant if we start early on a smaller plant. It is difficult to even obtain the concentration needed to be effective if we start late on a large plant.
Our end of April and first of May planted cotton will be approaching pinhead (PHS) to match head (MHS) square next week. On our good cotton soils where we have the ability to meet fertility and irrigation demands, applications of mepiquat chloride should be considered even if no recommendation for any pesticide is made. It is important to work to obtain the desired concentration of mepiquat chloride in the plant so that it may be maintained to effectively manage the crop.
On our most aggressive growing varieties, 16 ounces should be considered at PHS to MHS with possibly two more applications on a 10 day interval to set the plant up for balanced vegetative and reproductive development. Then monitor plants the remainder of the season and apply as needed.
Moving to the other end of the spectrum with our varieties that are the most responsive to mepiquat chloride, the rate could likely be cut to 8 ounces. Varieties with moderate growth habits should fall in the 10 to 12 ounce range. Subsequent applications should be made on an as needed basis.
There are many different and equally effective approaches for the use of products like mepiquat chloride in cotton. However, starting at the right time is the first step toward implementing a successful strategy. Remember, these compounds will not shrink cotton plants, but will only slow growth of actively growing tissue after application.
Our crop is growing fast and much like the saying that there is not much to do after the horse has already passed through the gate, don’t find yourself flat footed and let it run by you because it will be coming fast.