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Field and Forage Crops |
With the recent rainy, cool weather, most cotton growers are thankful that they have not begun planting. In most cotton fields thrips should be the only major cotton insect pest until initiation of squaring, although mites and cotton aphids can occasionally make an unwelcome appearance.
Producers often correctly associate high levels of migrating thrips with hot, dry weather. However, recent cool, rainy weather and lush plant growth may contribute to thrips outbreaks in a few weeks when significant cotton acreage is up and vulnerable to thrips injury. High amounts of early wild host vegetation (like fallow fields and ditch banks) as well as presently green wheat can help build thrips populations; the thrips then abandon these hosts in high numbers when hot weather returns, especially if the hot weather persists. If several consecutive weeks of hot, dry conditions coincide with the second and third weeks of cotton seedling development, high levels of thrips damage may occur in unprotected cotton.
Although weekly assessments of young cotton seedlings for thrips and their damage are recommended, thorough inspections at the emergence of the first true leaf and at approximately three weeks after planting are particularly important. The emergence of the first true leaf appears to be the time of maximum plant vulnerability, and three weeks after planting has consistently been close to the cut-off point for seed treatment activity, and automatic foliar insecticide treatments behind Gaucho and Cruiser are often justified with moderate to high levels of migrating thrips.
I will cover the specifics of making these thrips and thrips damage assessments in the upcoming issues of the North Carolina Pest News. Hopefully, by next week's cotton update, we will be blessed with warmer, dryer weather.
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 April 28, 2003 by Stephen J. Toth, Jr.