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Field and Forage Crops |
Although the bollworm moth flight is still on the low side throughout most of North Carolina, only a few scattered light traps are still showing much life. Still, most other counts are paltry. Most, but not all, conventional and Bt cotton fields are now safe from bollworm larvae resulting from eggs deposited this week.
However, as was mentioned last week, bollworm moths can still settle into cotton fields that are still attractive and susceptible in impressive numbers and their resulting eggs and larvae can still damage late and/or rank cotton fields. Be aware that the toxin(s) responsible for killing caterpillars in Bollgard, Bollgard II and in Widestrike Bt cotton may be running out by this time of year, so do not overlook the possibility of Bt cotton fields sustaining some late bollworm damage. In a stink bug test in Wayne County in untreated Bollgard II cotton, we were surprised to find approximately 3 percent second and third stage bollworms on or in young bolls and approximately 4 percent boll damage this morning. This is most unusual. In so far as possible, I would recommend checking all cotton fields, at least a final time, whether Bt or conventional.
In several of our stink bug tests, we are still getting stink bug damage to quarter-sized bolls in the 12 to 25 percent range in the untreated plots. One consultant in the Sampson County area also reported several cotton fields in the 20 percent plus range for stink bug damage, while another consultant in the Halifax County reported an isolated cotton field with over 50 percent damage to small bolls from a high population of plant bugs. Fortunately, these fields are generally few and far between, and stink bug and bollworm can be raised two to three fold in most fields at this time of year. However, this does point out the need to keep inspecting cotton fields that may still be vulnerable to bug damage.
Fall armyworms are still occurring in scattered locations, most commonly being noted in either white blooms or feeding on the inner surface of the bracts of medium to large bolls. Levels reported so far a modest. In North Carolina, after approximately September 1, fall armyworms seldom can become established to the extent of damaging bolls.
A few beet armyworms are also scattered about mostly as single larvae feeding on leaves or in blooms. This is a good sign. When anything approaching a treatable level of beet armyworms exists, large groupings of small beet armyworms can easily be found on foliage.
Hopefully by this time next week, the potential for further insect damage will have diminished considerably. At this time, however, insects are still taking a bite out of some cotton fields.
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Last modified on August 29, 2005 by Stephen J. Toth, Jr.