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Field and Forage Crops |
Recent weather, for the most part, has been good for planting cotton, although a few areas are still too wet to plant and other areas still a little dry. So far, both seed treatments and Temik are generally holding up well, though it is still early in the season. This situation is already starting to change, however, with thrips migrating from their drying host plants and moving into cotton. Some moderate levels of immature thrips are being reported, primarily following seed treatments.
We are now getting some initial telephone calls about thrips. One small sample of thrips, taken from unsprayed cotton in the Enfield area of Halifax County by a consultant, contained over 60 percent western flower thrips. Additional samples will be needed to determine if populations of hard-to-control western flower thrips may be more widespread.
If a foliar insecticide treatment is needed for thrips, plan on using the 4 ounce broadcast product rate (0.25 pounds of active ingredient per acre) of Orthene, or the equivalent. If western flower thrips are suspected, the 6 ounce product rate of Orthene (0.375 pounds of active ingredient), available to producers in the Carolinas and Virginia under a Section 2ee label, may be a good compromise between the 4 ounce rate for our common thrips species and the 8 ounce rate (0.5 pounds of active ingredient) generally recommended for western flower thrips. Rates can be reduced accordingly if banded. Unfortunately, western flower thrips cannot be identified in the field, and take some time even with the benefit of a good microscope. If a foliar treatment does not appear to control thrips, more often than not, the remaining population on the cotton seedlings is mostly western flower thrips. If the last few years are an indication, even though western flower thrips were found in a number of cotton fields the vast majority of cotton fields contained primarily other, easier-to-control thrips species, such as tobacco, soybean and onion thrips.
Generally, the hotter and drier the weather the more dramatic the thrips migrations will be in the coming weeks. With warm weather and adequate to good soil moisture, though, more rapid grow-off can at least shorten the time during which cotton seedlings remain susceptible to thrips damage.
As mentioned in last week's issue of the North Carolina Pest News, cotton planted with a seed treatment before about May 15 will likely need a foliar treatment at approximately the first true leaf stage. After about May 15 to 20, with good soil moisture and warm weather, seed treated cotton or the lower 3.5 pound rate of Temik may suffice. Using both a seed treatment and a low rate of Temik combined has not been cost effective in replicated university trials here.
Weekly inspections of cotton seedlings from the cotyledon to about the four or five true leaf stage are recommended. If an average of one or more of the small, wingless, yellow-colored immature thrips are found per seedling, a foliar treatment is probably needed, especially if associated with deformed new leaves.
In North Carolina, adult migrating thrips populations are often highest during the last two weeks in May and the first few days in June. By next week's update, we should be getting a much better idea of how the thrips season is shaping up.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on May 19, 2003 by Stephen J. Toth, Jr.