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This is Jack Bacheler, Extension Entomologist at North Carolina State University with the Wednesday Cotton Insect Update. Today is Wednesday, June 8.
Between much of our cotton getting to the five true leaf stage and beyond and declining levels of adult migrating thrips, our “thrips season” is coming to an end. Even the untreated check plots in May 4-planted research tests near Rocky Mount that have been badly damaged by thrips were beginning to show signs of new shiny leaf growth yesterday. This is an indication of no or limited thrips damage. That’s not to say that this cotton looked pretty, however.
With the prospect of selling cotton for a good price this year if the weather decides to cooperate, many growers will be tempted to spray cotton one last time “for the Gipper”. These revenge or recreational sprays will often do more harm than good. Most of the beat-up cotton that we have examined this past week had non-existent or low levels of immature thrips. Additionally, all of the main products used for thrips control (such as Orthene, Bidrin, dimethoate, Vydate and others) increase the odds of treating later for cotton aphids and/or spider mites.
Before any foliar treatment, be sure to examine cotton seedlings, either with a hand lens or by beating a handful of seedlings over a flat surface, for the presence of immature thrips. If less than one immature thrips per true leaf per plant is present, do not treat. Additionally, treating cotton seedlings with 5 or more true leaves, even with moderate to high levels of thrips, is not justified economically.
In most years, cotton insect management now turns to plant bugs, cotton aphids and spider mites. As cotton begins to square, be sure to take square retention counts. We often find square retention in the 95-100% range early in the square reduction period. Square retention counts less that 80% indicate the possible presence of plants bugs and more detailed assessments for this pest.
Although we have received a few calls about cotton fleahoppers and grasshoppers this past week, so far none has been found at economic levels.
We’ll have information about managing plant bugs and other cotton pests in the coming weeks. See you next week on June 15. See you then.