Cotton Insect Newsletter Vol. 20, No. 11, July 31, 2002 Call 1-877-629-1474 for Cotton Insect Hotline

Cotton Situation: A large portion of the state's cotton acreage has just about done all it's going to do.  Moisture has been the main limiting factor, as plants are stunted, and the bolls will be difficult to pick when they open up since they are located so close to the ground.  At least, there shouldn't be any boll rot to worry about.   As usual, there are some areas of the state that have received sufficient rainfall to produce healthy plants that have good yield potential.  Insect control will be a main concern where plants still have five or more nodes above white blooms.  Such plants are going to be more attractive to bollworm and budworm moths, stink bugs, and fall armyworm moths.  The drought stressed plants will be less attractive to the former insects, but spider mites and beet armyworm moths often prefer such conditions.  Insect Situation: Bollworm egg numbers appeared to be somewhat lower over the weekend, but by July 30 scouts were seeing increased numbers in cotton.  Pheromone traps are still capturing some comparatively large numbers of bollworm moths in some areas.  This is the time of year when generations tend to overlap, so we will soon be seeing the beginning of the next generation of moths.       Egg deposition in Bt varieties won't differ much from conventional cotton, although the actual numbers may be higher if a field is not being sprayed.  Most conventional cotton fields that are not being used as refugia will have been sprayed two or three times with pyrethroids by now, which would kill some of the moths and perhaps, would keep the egg numbers at somewhat lower levels than in a Bt field that had not been treated.   In research conducted in 1997 and 1998, we investigated egg deposition preferences by bollworm/ budworm moths for different plant structures.  We looked at terminals, expanded leaves, stems and petioles, squares and bracts, bolls and bracts, white blooms and pink blooms.   To no one's surprise, we found that bollworm/budworm moths lay most of their eggs on terminal growth and expanded leaves.  We found that a scout who looked only at terminals would have consistently detected 20 to 35% of the eggs deposited on the whole plants.   A generally lower percentage of eggs was deposited on, or near, fruiting structures, but this was relatively consistent between the Bt variety (Dpl 33B) and the conventional variety (Dpl 5415).  Over 20% of the eggs were laid on bloom tags on July 30, 1998 when data was averaged across three locations.  This shows why it so important to conduct whole-plant observations at this time of year, or even earlier in drought-stressed cotton.   We also found that egg parasitism by a wasp, Trichogramma spp., was nearly 50% in eggs that were collected in late July and early August.  No conclusions could be drawn concerning the levels of parasitism in cotton varieties with and without the Bt gene, but it stands to reason that a Bt field that has not been sprayed for bollworms would provide a more hospitable environment for the tiny wasps. Beet armyworms are still hanging around in some fields, where they have been entrenched since early June.  We are still picking up some new egg masses in cotton fields, and relatively high numbers of moths are being captured in pheromone traps.   I received a request to pursue a Section-18 Emergency Exemption for Denim in South Carolina.  Denim is an insecticide that has performed very well against beet armyworms.  It is currently being used under a Section-18 label in Mississippi and a few other states.  We have not pursued a Section 18 previously, since no emergency was expected after last year, when we didn't see any beet armyworms.  As this year has progressed, beet armyworms have become a more important pest, and it would certainly have been helpful for farmers to have another insecticide; however, after checking with EPA and the SC Department of Pesticide Regulation, the best we could probably do would take over 50 days.  Therefore, I will not submit a Section 18 request at this time.  If Denim does not have its full registration for cotton next year (or very good prospects for one), a request will be submitted to EPA in time to have the material by the time it's needed.      Stink bug numbers seem to be somewhat lower than has been the case in recent years.  Still, I would continue to expect an influx of stink bugs into cotton fields over the next few weeks.  It's too early to relax your guard.   Boll Weevil Program: I had the opportunity to chat briefly with Randy Lynch this morning.  It seems that the program is going very well in South Carolina.  Most growers have been very cooperative in opening access ways for workers to service their traps.   Trap destruction by farm equipment is still a problem and it would be good for the program if this could be minimized, especially now that cotton is maturing and boll weevils will be moving.   As of today, there have been no weevils captured in South Carolina, North Carolina, Georgia, or Florida.  There may have been a few captured in Alabama, but numbers there have been the lowest yet recorded.   Mitchell Roof  Extension Entomologist

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