Cotton Pest Management Newsletter #8
July 25, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending July 21^st listed the crop as 78 percent setting bolls. Yield potential is extremely varied due primarily to available moisture. Crop conditions continue to be listed fair to good (87 percent rated fair or better). Early planted dryland fields have cut out in some areas and a few fields with open bolls have been reported.

Insect Situation: The insect situation has not changed much during the last week. Most areas are observing a mixture of both tobacco budworm and corn earworm in addition to various armyworm species. Treatments for bugs are being made in many areas. Pressure continues to be moderate but fairly widespread.

Tobacco Budworm and Corn Earworm (Non-Bt Cotton): We continue to receive reports of difficulty controlling tobacco budworm (TBW) with pyrethroids. A non-pyrethroid insecticide such as Steward or Tracer should be used for control of TBW. Corn earworm (CEW) or TBW? Which species is infesting the field? This is a difficult question and often during late July and August there may be a mix of both CEW and TBW. Knowing which species is the primary target can greatly influence insecticide selection and cost of a treatment. Information obtained from moth flushing counts, commercially available egg identification kits (AgDia), and/or pheromone trap counts may aid in estimating species composition. In some areas, we have observed TBW survival behind sprays when the majority of moths observed were CEW. When dealing with mixed populations, options for control include using either Steward or Tracer alone or a tank-mix of a pyrethroid with a low rate of Steward or Tracer. The tank-mix has performed well and will also control bug pests which may also be infesting the field.

Bt Cotton: We continue to receive a few reports of Bt cotton requiring supplemental treatment for CEW. Scouts should pay special attention to blooms and under dried blooms. Often, escaped larvae will penetrate the tips of bolls which are covered by the drying flower. Pyrethroids have provided good control of CEW in Bt cotton.

"Bug" Damage: Scouts should be monitoring medium sized bolls for internal signs of feeding (stained lint and/or warts on the inner surface of the boll wall). Bolls approximately the diameter of a quarter should be monitored for internal damage when scouting for bugs. Bolls of this size can be easily squashed in the palm of your hand. If bolls are difficult to squash, they are too old to sample as what damage is present may have occurred weeks ago. All fields which have bolls of the appropriate size should be scouted for bugs. Scouts should also be observant for which bug species is infesting fields. In addition to stink bugs, plant bugs and leaf-footed bugs will also feed on developing bolls. Often we will observe high populations of stink bugs in border rows of cotton fields next to a peanut or corn planting. So if you are unsure about what stink bug damage looks like, this is a likely place to look. Recommended treatments for stink bugs include the pyrethroids, Bidrin, methyl parathion, Orthene, and Vydate. The threshold is 20% internal damage and stink bugs observed or 1 stink bug per 6 row feet.

"Dirty" Blooms: In fields visited this week we have observed a few "dirty" blooms. Dirty blooms are the result of plant bug feeding on large squares which the plant does not shed. When the bloom opens, darkened anthers and warty spots can be seen on the petals. In fields where the dirty blooms were found, low populations of large plant bug nymphs were observed. Dirty blooms can result in poor pollination and deformed bolls. Insecticide treatment is recommended in Alabama if 15 percent dirty blooms are observed.

Armyworms: Various species of armyworms have been reported in fields during the past week. Beet, fall, southern, and a few yellow-striped armyworms have been observed. Proper identification is important as insecticide susceptibility varies among species.

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