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Field and Forage Crops |
Cotton insect pests most likely to be encountered from mid to late June include plant bugs, tobacco budworms, cotton aphids, and spider mites. In most cases, these pests result in few economic damage problems compared to our mid to late-July and August pests such as bollworms and stink bugs.
Square retention rates remain our most reliable means of tracking possible plant bug damage to pre-blooming cotton. Generally, if square retention is 80 percent or more (very common in North Carolina), further sweeping for plant bugs is not necessary. If the retention rate is less than 80 percent, sweepings in randomly selected areas of the field should help determine the need to treat with insecticide. On the average, approximately 5 percent of the state's cotton acreage is treated annually for plant bugs during the pre-bloom period, but occasionally cotton fields, especially in some of our far eastern counties, can sustain significant fruit loss in both the pre-blooming and blooming period.
Tobacco budworms feeding in terminals and on squares in June more often than not results in damage for which cotton plants can compensate. Additionally beneficial insects often take a significant toll on this budworm generation. However, if 15 percent or more live budworms are present in terminals or 10 percent in squares, treatment with non-pyrethroid insecticides such as Tracer or Steward may be needed. Budworm infestations on cotton so far have not been as early or as common as had been expected.
Low-level cotton aphid infestations appear to be widespread at this time indicating the potential for significant outbreaks, especially given the high level of earlier foliar insecticide applications for thrips. Fortunately, in the Carolinas and Virginia, natural control of cotton aphids by a small mummifying wasp parasite and a fungus is a common occurrence. However, if cotton is under stress, honeydew is easy to find, large aphid colonies are present on most plants, and no signs of aphid mummies or the fungus are present, then treatment may be advisable. Any of the new aphid insecticides, such as Provado, Centric or Intruder, should provide good aphid control, especially with ground equipment.
With continued hot, dry weather across much of North Carolina (helped along by foliar insecticide treatments for thrips), reports of spider mite damage have become more numerous during the past week. In areas of the state where moisture levels are good (primarily in the eastern counties) or timely rainfall occurs, mite outbreaks are less likely. Treatment for mites is typically both expensive and not very satisfactory, but may be needed in cases where yellow to bronze-colored leaves are present, significant defoliation is noted, and an active mite infestation is present throughout most of the field. Because a common moisture-loving fungus can reduce mite levels dramatically, do not spray if rain is likely.
Areas in the state that have received some rainfall are the lucky ones. Other areas remain dry and previous thrips injury is still putting a stunting effect on these peanut plants as they try to recover. Spider mites are creeping into some areas and a few areas are dry enough that growers need to keep a watch for lesser cornstalk borers. I really have not seen many of them since 1980, but keep a watch for wilting vines and the silk tubes they create. We are finding plenty of virus in the small peanuts and it does indicate there will be no shortage of virus in peanuts this year.
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 June 24, 2002 by Stephen J. Toth, Jr.