Cotton Insect Newsletter Vol. 18, No. 12,  August 9, 2000 call 1-877-629-1474 for Cotton Insect Hotline

Cotton Situation:  Most of the early-planted cotton has done about all it is going to do at this time. Following some rather heavy showers with wind last week, we saw some of our cotton plots at the PDREC were flattened by strong winds.  It hasn't been the best of years, but there are some good sized bolls on these plants, and I doubt seriously if they can pull themselves off the ground.   Bolls are starting to open in some of the earliest cotton, especially in areas where drought stresses have been severe.   The latest-planted cotton is about to begin the second week of setting bolls.  Time is running out, but if rain keeps coming and Jack Frost is late, we could see some good yields in June planted cotton. Insect Situation: Scouts reported some renewed activity by bollworms in cotton plots here at the station.  Up to 40 or more eggs per 100 plants were reported in some plantings.   I would expect to see a steady increase in egg numbers during the next several days where cotton still has lush growth in terminals to attract the moths.  There are some areas of the state below the lakes, especially in irrigated cotton, where the bollworms just keep coming and egg counts have remained relatively high since early July.  In fields where plants have little to offer but bolls, egg deposition should be minimal.  Late maturing cotton will continue to be attractive to moths into September.  Soybeans are pulling moths away from cotton to some extent.  I saw plenty of moths and eggs in blooming soybeans this morning.  Stink bug numbers appear to have declined in most of the fields that have been sprayed two or more times with pyrethroids, however, they are fully capable of mounting another attack, so do continue to scout for damaged bolls.  I haven't heard any reports this week of fall armyworm infestations or beet armyworms, but it's more than likely that some fields will have economic infestations, either already there or building.   There have been some heavy infestations of beet armyworms reported from Texas, Louisiana and Mississippi, so it wouldn't be too surprising if a flock of moths found there way to South Carolina by riding on a rapidly moving weather front.  The same scenario could occur with soybean loopers, although I have yet to hear of any major infestations from our neighbors to the south.  Aphid numbers were starting to build up some last week, but heavy rains did a good job of knocking them off the plants. Section 18 for Steward: We were notified some time ago that Steward 1.25 SC (DuPont) was granted a Section 18 exemption for 2000.  It wasn't until yesterday that I received a copy of the Section 18 label.  The label states that Steward can be used to control budworm, bollworm and beet armyworms.  No more than 0.44 lb ai/acre may be used during this season.  The rate for budworm and bollworm is 11.3 oz/acre and 9.2 to 11.3 oz/acre may be used for the control of beet armyworm.   Steward should be in the same ball park with Tracer and Larvin for control of bollworm, both for efficacy and cost.  It will be comparable to Tracer for beet armyworm control and rain-fastness and of course, both of these materials will be more resistant to rain-off than Larvin.  The Section 18 label does not mention fall armyworm or soybean looper, but Steward should do a good job of controlling these pests where they are mixed in with the target species. We petitioned EPA for a Section 18 for Steward primarily because it is an alternative to the pyrethroids in the event that widespread resistance problems were to occur with bollworms.  Also, we fully expected to see some severe beet armyworm infestations.  Trap reports from Mississippi and Texas indicated that moth captures were unusually high in the winter and spring.   To date, we haven't seen any widespread problems with beets or resistant bollworms in South Carolina, but if these should occur, farmers will have another control option.   Seed Rot: There seems to be a much lower incidence of seed rot compared with findings from 1999.  Last year County Agents collected bolls from fields in all the cotton-growing counties in South Carolina, and each boll was dissected and examined for seed rot and stink bug damage.  A similar survey will be conducted this year to determine the incidence of these pests. Bt Refugia: It may be a little late to be talking about the refuge requirements for Bt cotton, but I feel that we need to adhere to these requirements or we will end up facing something even more restrictive.  I doubt there is any problem with the 25% sprayed refuge; it's the 4 acres of unsprayed refuge for every 100 acres of Bollgard cotton that needs attention.  Those refuge acres may only be treated with insecticides that do not provide bollworm control.  For example, you could spray these fields with Bidrin or methyl parathion for stink bug control, but you couldn't use Tracer for beet armyworm control since this material will control budworms and bollworms.  The idea of the refuge is to build up populations of susceptible bollworms, so they would be available to mate with any resistant individuals that showed up in Bt cotton fields.  The offspring of such matings would be susceptible to the Bt toxin.  If resistant moths mated, some of the offspring would be resistant as well.  Therefore, resistance levels would increase at a faster rate where the proportion of susceptible moths was low.  In other words, we need the unsprayed refuge and the 25% conventional sprayed refuge to forestall the development of resistance to the Bt toxin. Boll Weevil Containment: Keep an eye out for cotton fields without pheromone traps.  Boll weevils will be moving if there are any around.  Call Randal Lynch at 1-800-269-9928 to report a problem.   Mitchell Roof  Extension Entomologist

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