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Field and Forage Crops |
Beet armyworms are still present throughout much of the cotton acreage in North Carolina. We can probably expect the presence of beet armyworms until defoliation and harvest (on regrowth). Continued drought conditions across much of the state certainly isn't helping beet armyworm control. In addition to significantly depressing yields, the prolonged dry weather also favors beet armyworm survival, even on cotton that has completely cut out.
In cotton that has cut out to the extent that squares and blooms are hard to find, a treatment threshold of at least 15 to 20 percent beet armyworms on small bolls may be appropriate. Also, treatment may be advisable if beet armyworm foliage feeding is threatening the important leaves at the base of small to medium developing bolls. This situation takes a lot of beet armyworms, and hopefully, will not be met often. Other defoliation, even though easy to spot, is not likely to be economically damaging. On rare occasions, with extremely high beet armyworm levels of more than one per boll, the potential of damage to the boll stem or outer surface may favor treatment. On the other hand, a large number of cotton fields are so dry that either the small bolls have already been shed, are shedding presently, or will be shed once we get significant rainfall. Under these conditions, treatment is hard to justify. If bolls are not threatened, do not treat for beet armyworm defoliation. treatment for leaf and/or feeding
Reports of stink bugs and their damage, although much lower than either in 2000 or 2001, have increased this during the past two weeks. However, a high proportion of our cotton fields are no longer susceptible to stink bugs or bollworms; that is, the ratio of large speckled bolls to smaller bolls is so high that adjusted threshold levels would only rarely be met. Treatment thresholds should be raised according to the number of insect-safe bolls present in cotton fields. With stink bugs, for example, if large mature bolls outnumber smaller bolls by a 8:1 ratio, a level of approximately 80 to 90 percent damage to quarter-sized would needed to justify treatment. Pyrethroids are the insecticides of choice for bollworms and green stink bugs, while Intrepid insecticide is preferred for beet armyworms.
The next bollworm moth flight is probably underway, but probably will have little impact on cotton except for late maturing cotton fields. Our mid to late August and September moth flights are typically much lighter and less synchronous than the previous generation.
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Last modified on August 19, 2002 by Stephen J. Toth, Jr.