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Field and Forage Crops |
Beet armyworms continue to persist on cotton and other crops, and will likely do so until significant rainy weather and/or cotton cut out occurs. This is the most widespread beet armyworm outbreak I have seen in my 30 years at North Carolina State University. Intrepid at 4.0 ounces of product per acre remains the most effective product available for beet armyworm control. At this point in the season, if cut out is well underway, especially to the point of lateral squares and blooms being difficult to find, beet armyworm spray decisions are probably best determined by defoliation. If beet armyworms are plentiful enough in cutting out cotton to cause significant defoliation of leaves at the base of (subtending) bolls which are still filling out, spraying may be indicated. These leaves are necessary for boll nutrition and maturity. In cotton fields which still have significant levels of white blooms, 10 percent live beet armyworms in squares and bolls, and beet armyworms easy to find in white blooms (perhaps every other bloom), treatment may be needed.
For the most part, the bollworm flight is down considerably in southern North Carolina. However, levels remain high enough in many areas to account for significant egg deposition and bollworm survival in cotton fields which are still attractive and susceptible. At this time of year, it is important to consider the proportion of large, speckled mature bolls to those which are still vulnerable to bollworms and stink bugs. For example, if these mature bolls outnumber the smaller bolls by a 3:1 ratio, a 3 percent bollworm treatment threshold would become 12 percent live bollworms.
Treatable levels of mostly green stink bugs have begun occurring this past week, although levels still appear well below those of 2000 and 2001. Stink bugs can often persist in attractive cotton fields well into August and even September. However, the same boll size considerations are appropriate with stink bugs as with bollworms.
Although the aphid fungus, Neozygites fresenii, now seems to be containing most of the cotton aphids outbreaks, treatable levels have still been reported this past week. For the past 6 years or so, aphids levels have been present at very low levels in opening cotton (a time of increased crop susceptibility due to sooty mold on lint due to honeydew and sticky cotton). Very few fields of opening cotton have been treated in recent years.
Caterpillars continue to cause concern to peanut growers. The most significant aspect of the caterpillar infestations is the composition. Many fields have a large number of beet armyworms this year. These insects are much more difficult to control than are corn earworms and even fall armyworms. The threshold will remain at around 4 to 6 armyworms per row foot through August. Lannate will provide reasonable control of beet armyworms if the infestation is caught when the armyworms are very small in size. Unfortunately, this does not occur very often. Steward recently received a label for peanuts and is working well against this pest. This product must be ingested by the insects and may take several days to show its true effect. Ames Herbert at Virginia Tech University has some data on Steward against leafhoppers and he has seen a definite reduction in leafhoppers as well.
Beet armyworms are an unusual problem in peanuts. There are still a lot of moths flying around and we may see another round of problems. Be sure to continue to scout fields for the next month and respond in a timely manner.
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Last modified on August 12, 2002 by Stephen J. Toth, Jr.