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Field and Forage Crops |
Light trap counts continue to be moderate to high throughout approximately the lower three-fourths of the state. Although trap counts in several southern North Carolina counties have leveled off in recent days, more than enough moths are present in most areas to account for egg and bollworm thresholds to be met. As I mentioned last week, threshold levels of eggs and bollworms are being primarily found on fruit, often associated with pink and dried flowers stuck to blooms.
Beet armyworms continue to cause grower headaches in scattered areas throughout the state. Because pyrethroids offer little or no control of beet armyworms and destroy most species of beneficial insects and with pyrethroid sprays now well underway in at least the lower half of North Carolina, beet armyworm outbreaks may well increase in areas where significant rainfall has not come to the rescue. Fortunately, the generous rainfall received across much of the state should help reduce beet armyworm levels significantly. A threshold of approximately 10 percent beet armyworms on squares or young bolls and beet armyworms easy to find in white blooms may be appropriate since cotton is very vulnerable to fruit loss at this time in its development. To control beet armyworms, a tank mix of Intrepid at 4 ounces per acre plus a pyrethroid where bollworm thresholds are present, or high-labeled rates of either Steward or Tracer, is recommended. Intrepid will probably provide better control of medium and large beet armyworms than either Tracer or Steward but is weak on bollworms, while Tracer and Steward alone generally provide fair to good control of bollworms at these higher rates.
Scattered fall armyworm reports have come to our attention in the past week, though so far populations have been light on cotton. Fall armyworms have caused rather extensive damage to pastures, however, and fall armyworms can build up on cotton during August. Often the first sign of a fall armyworm infestation are the finding of small feet armyworm feeding on the inner surfaces of boll bracts. Once established in blooms or bolls, fall armyworms are very difficult to control with insecticides. Some pyrethroids (Capture and Karate) seem to be more effective than others (Asana and Baythroid) in keeping hatching fall armyworms from becoming established when applied for bollworm control, although all pyrethroids appear to offer some suppression of young fall armyworms (less is known about Decis and Fury). The addition of 10 to 26 ounces per acre of Larvin tank mixed with a pyrethroid has helped control small fall armyworms. Lorsban and Curacron may also fit this situation. The new materials Intrepid, Steward and Tracer also have fall armyworm activity, but we have less experience with these materials in North Carolina.
At this time, stink and plant bug reports are down from the past two years. However, we are just coming into the time period when stink bugs and plant bugs typically make their presence known on Bollgard cotton. This year, I recommend a threshold of 10 percent internally-damaged, quarter-sized bolls, counting both stained lint and warts on the inner boll wall surface but not the external spotting. On Bollgard cotton in North Carolina, stink bugs and plant bugs together have accounted for about 2 to 3-fold higher damaged boll levels than bollworms since 1996. Cutting open 50 quarter-sized bolls is highly recommended in Bollgard cotton. In treatable situations, if brown stink bugs are more abundant than the typically more common green stink bugs, Bidrin may be needed.
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 July 29, 2002 by Stephen J. Toth, Jr.
