Cotton Pest Management Newsletter #14
August 30, 2001

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending August 26^th listed the crop as 18% with open bolls. Crop conditions remain fair to good, but some areas are very dry.

Insect Situation: Much of the insect activity is occurring on later planted fields at this time. Tobacco budworm, corn earworm, loopers, and low numbers of fall armyworms are infesting fields at this time. Stink bugs continue to be a primary pest in some areas.

Tobacco Budworm and Corn Earworm: Mixed populations of tobacco budworm (TBW) and corn earworm (CEW) are occurring in various parts of the state. During the last week to ten days, increased activity has occurred in the central part of the state. In some situations, growers are having difficulty achieving acceptable control with pyrethroids. It appears that CEW is being controlled and TBW is the problem. This has occurred primarily when pyrethroids have been used alone, but also when high ovicide rates have been tank mixed with pyrethroids in some fields. We know pyrethroid resistant TBW is a potential cause of poor control and thus would encourage the use of alternative treatments such as Tracer or Steward if pyrethroid resistant TBW is suspected. However, we must also remember the importance of application timing and other factors which may influence control. Tracer and Steward are not considered cleanup treatments and should target small larvae. Egg and larval counts are concentrated on late planted cotton which is still lush and green at this time. Cotton which has cuttout is not an attractive oviposition site. TBW and CEW must be managed until the last harvestable boll is at least 20 days of age. At that time bolls are not immune from TBW and CEW attack, but the likelihood of significant damage is reduced.

Stink Bugs: Stink bugs should continue to be scouted until the last cohort of harvestable bolls which will significantly contribute to yield has attained 20-25 days of age. Bolls of this age will be difficult to squash in the palm of your hand and be fully sized. Stink bugs are still capable of feeding on bolls of any age, but research conducted during the past two years indicated that no significant yield decrease occurred on bolls greater than 25 days of age when they were fed upon by stink bugs. Stink bugs can penetrate through pecans after shell hardening. When making management decisions for stink bugs, one must also consider how many susceptible bolls are in the field. It is common to see our boll damage count increase when few quarter sized bolls are present in a field. If a scout must hunt for quarter sized bolls the 20% internal damage threshold should be raised as our damage count will be somewhat inflated since feeding will be concentrated on the younger bolls. Additionally, the number of bolls per acre we would be protecting would be lower and thus, of less value.

Soybean Looper: We have received several reports of soybean loopers (SBL) in various parts of the state. SBL moths were very numerous in some fields this week. SBLs are foliage feeders and initially feed low in the plant canopy and work their way up the plant in time. In some situations moderate defoliation low in the plant canopy can actually be beneficial. But if immature bolls are present in the top of the plant, we must protect the foliage which is feeding those bolls. A large percentage of the foliage consumed by loopers occurs during the later instars (larger larvae). Defoliation can occur rather quickly and fields should be watched closely, especially if populations are greater that 4 per row foot. Observations suggest that economic damage may occur as numbers approach 8 per row foot. Decision to treat should be based on defoliation and the presence of immature bolls. Tracer and Steward are two options for control of SBL.

Boll Weevil Eradication Update: As producers cleanup field margins in preparation for harvest, we need to remind them of the importance that boll weevil traps are standing and functional. If a trap is accidentally knocked down, please stand it back up. Additionally, if traps are accidentally destroyed the boll weevil eradication personnel should be contacted so that a new trap can be installed. It is especially important that traps are standing and functional this time of year. If you remember back to the boll weevil days when fields cuttout, weevils scattered in search of new food sources and traps would fill up in a day. Most reinfestations since eradication have been found during August as cotton cuts out. Last week, four boll weevils were trapped in Turner County. To date this is the only known reinfestation in Georgia. The BWEP quickly responded to this situation with intensive trapping of the surrounding area and infield trapping in addition to malathion sprays on a limited acreage. We have never gone a complete year without capturing a boll weevil in Georgia since eradication. Early detection and control of reinfestations is only possible with vigilant trapping on all fields and is vitally important to maintaining our weevil free status.

Silverleaf Whitefly: Silverleaf whitefly (SLWF) are still present in fields in the Tifton vicinity. Continue to monitor development of populations closely in infested fields, especially on late planted fields. As defoliation begins we will see numbers concentrate on green lush fields.

Last Cotton Pest Management Newsletter: This is the last issue of the Cotton Pest Management Newsletter. I would like to thank all individuals who updated us on current insect situations. Hopefully the information we provide has benefited you. We will continue to update the Insect Hotline on an as needed basis.

Insect Updates: Check the Cotton Insect Hotline (1/800-851-2847) for updates on current insect conditions. The Cotton Pest Management Newsletter is also posted on the Internet at www.gaipm.org and then click on "cotton."

Sincerely,

Phillip Roberts
Extension Entomologist