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Field and Forage Crops |
Although not always true in a given year, the value of using an at-planting insecticide to reduce thrips damage will outweigh the cost of the material in the long run. The use of either Gaucho or Cruiser seed treatment will probably require additional spray protection for thrips, but these products can be cost effective, especially with Roundup Ready and Liberty cotton (if applied early). Temik 15G at the 5 pound of product rate remains North Carolina's standard for thrips control, and will less likely require foliar protection for thrips than the seed treatments. Each of these three insecticide products should provide cotton aphid protection for four or five weeks, or more.
Most of our foliar spray treatments for thrips (such as Orthene), while often needed during the past three years' thripy springs, will sometimes increase cotton aphid numbers. We do not recommend the use of foliar sprays alone in conventional row cotton. Ultra narrow row cotton, with it's high in row seed protectant costs, is an exception; although Temik at low rates and a seed treatment plus a foliar application were competitive to the foliar spray alone approach in ultra narrow row cotton in replicated tests conducted here in 1997.
With our recent history of early and high levels of thrips, do not overlook the possibility of thrips establishment and damage as early as the expanded cotyledon to the first true leaf stage. Surprisingly, last year we found moderate to high thrips levels on cotton seedlings just coming out of the ground. So these insects can begin early.
Remember that thrips is a pest group that must be taken seriously in the Carolinas and Virginia, and measures to protect cotyledon to 4 to 5 true leaf cotton seedlings from significant thrips damage are usually justified.
In various forms of conservation tillage (such as stale seedbeds, no-till or strip till), weed residue (especially if burned down less that 2.5 or 3 weeks of planting) can support damaging levels of cutworms, which can then move onto the remaining green foliage -- cotton seedlings. Scouting for cutworms and treatment based on a stand loss of about 10 percent along with live cutworms is recommended where possible, although the thoroughness of the scout, the size of the cutworms, the distribution of the damage, and the density of the plant stand itself should be taken into consideration. Cutworm scouting is difficult, as these caterpillars invariably hide out below the soil surface under clumps or within cracks.
A history of cutworm damage in a conservation tillage cotton field, if known, may argue for insecticide treatment. This can be done cheaply with a broadcast or banded pyrethroid application prior to, during, or just after planting. In general, however, significant cutworm reductions to stands are much more the exception than the rule in reduced tillage cotton.
Grasshoppers, an occasional problem in conservation tillage cotton, have been at low levels so far this spring in states to the south where cotton has been in the field for a while.
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 5, 2003 by Stephen J. Toth, Jr.