North Carolina Cotton: Time to Watch for Thrips

Thrips damaged cotton. Photo: University of Georgia

This planting season has been frustrating to say the least. We had a 5-day stretch of good planting weather during May 13-17, 2020, and intermittently at other times during May, as planting was interrupted by abnormally cool spells or exceptionally wet weather throughout the duration of most of our typical planting window.

Regardless of when it was planted, there isn’t much difference in plant size at this point in time. Currently, the 2020 crop is noticeably later than normal, both in planting and in crop development.

Cotton planted in early May should be nearing the squaring stage by mid-June in most years, whereas this year, nearly all cotton is anywhere from cotyledon to 1-3 very small true leaves in early June, regardless of when it was planted.

Needless to say, slow growth has plagued our crop thus far, which is the likely product of adverse weather during most of May, probable herbicide injury in some cases, and other stresses.

There have been many reports of thrips already, including immatures, which is no surprise for earlier planted cotton where infurrow liquids or seed treatments have long expired. If you haven’t already, be scouting and/or treating when needed, and many fields will (or already do) need treatment.

Timely management will be critical for managing this crop this year. It pays to be timely regardless of when cotton is planted, however acceptable yields can be achieved in earlier planted cotton with a normal growth curve because losses are often unnoticed.

With a later maturing crop with delayed growth, these losses will be magnified if management is not timely. The crop is noticeably behind schedule, therefore growers cannot afford to:

  • be late on any necessary sprays for thrips, lygus, bollworms, stinkbugs, etc.
  • allow for excessive growth due to delayed PGR applications (when such applications are needed)
  • further delay maturity with excessive fertilizer rates or delayed applications or any injurious fertilizer or herbicide injury that could cause fruit to abort
  • allow extended competition from troublesome weeds.

The focus for the foreseeable future being should be to manage for earliness by retaining as many fruit as possible as we progress into the squaring stage and then into bloom. This is best done through thorough and frequent scouting, and very timely management, while avoiding practices that will further set the crop back.

For thrips, early sprays are the most effective (when the cotyledons can be peeled back to expose the first emerging leaf). If you can find immatures and have small cotton (less than four or five true leaves), consider the seed treatment or infurrow played out and plan for a spray.

Expect more injury from postemergence herbicide tank mixtures

Because most residual herbicides applied at planting have been “washed out” due to abnormally wet weather, many growers will need to add a residual herbicide (Dual Magnum, Outlook, or Warrant) in their first trips across the field. These herbicides will likely be combined with postemergence (POST) herbicides and a foliar thrips product.

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In my experience, cotton injury from these tank mixtures is largely influenced by environmental conditions, more specifically soil moisture. When soils are saturated and cotton plants are tender, growers should expect more burn from postemergence combinations. However, do not let this discourage you from applying these tank mixtures.

Even in a worst-case scenario where cotton is injured 30 to 35% five days after application, previous research has demonstrated yield is not affected. If you are overly cautious and insist on split applications to avoid injury, I suggest first removing emerged weeds and thrips with your POST herbicide(s) and thrips product of choice.

A couple days to a week later, apply Dual Magnum, Outlook, or Warrant, being sure to get your residual herbicide activated prior to germination of new weeds.




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