Cotton Pest Management Newsletter #4
June 20, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending June 16^th listed the crop as 43 percent squaring and 8 percent setting bolls. Crop conditions were generally listed fair to good, but many areas are in need of moisture very soon.

Insect Situation: Aphid populations are building in parts of the state. Scattered reports of beet armyworm activity continue to be received. There is indication that the second generation of tobacco budworm is starting to infest cotton in southernmost Georgia.

Aphids: Aphid populations are building in various fields across the state. In most situations there are small areas of fields (early infested plants) with high infestations. However, some fields have fairly uniform infestations and honeydew is accumulating on lower leaves.

Cotton aphids are very prolific, a new generation may occur every five days. In the early part of an infestation, winged aphids infest plants and give birth to living young that develop into wingless females. Wingless females will continue to give birth to wingless forms until the host plant becomes crowded at which time females will give birth to living young that will develop wings so that they may fly to infest other plants. These soft bodied insects range in color from light yellow to dark green or almost black and infest the underside of leaves and/or tender terminal growth. Damage to the plant occurs as aphids feed on plant juices with their sucking mouthparts. This feeding is an additional stress factor on the plant. Heavy feeding will cause discoloration or yellowing of the terminal. Aphids secrete a sugar-like substance called honeydew which makes the leaves sticky and slick in appearance. A sooty mold will develop on accumulated honeydew.

Aphid trials conducted in recent years have typically shown no yield benefit to treating aphids. However, there appears to be some heavily infested fields in parts of Georgia which may justify treatment at this time. The decision to treat aphids is a difficult one and is basically a judgement call which must be made on a field by field basis. Aphids would need to be severe in non-Bt cotton to justify treatment as beneficials are vitally important in this system. In making the decision to treat aphids, we would suggest you consider the following symptoms: heavy honeydew present and some leaves showing sooty mold, yellowing in the terminal or lower leaves, retention problems on stressed cotton, or limited growth on late planted cotton. Additionally, treatment would only be considered if no reports of the fungus which causes aphid populations to crash have been received. Ideally we would like to wait on the naturally occurring fungus to control aphids. The first report of the fungus which causes aphids to crash was July 1 in 1999, July 5 in 2000 and June 25 in 2001. When the fungal epizootic will occur this year can not be predicted, but scouts should be observant for grayish fuzzy aphids which is indicative of the fungal epizootic. Once the fungus is present in the field, populations will generally crash in about a week.

The neonicotinoid class of insecticide has demonstrated good activity on aphids and includes Centric, Intruder, and Trimax. These insecticides would be good options if consideration is being given to treating aphids.

Several county agents and consultants are participating in a Cotton Aphid Fungus Sampling Service being coordinated by Dr. Don Steinkraus of the University of Arkansas in cooperation with Cotton Incorporated. Results of samples sent from Georgia and other states will be posted on a web site by the University of Arkansas (http://www.uark.edu/misc/aphid). There is also information on how to participate in the sampling program.

Tobacco Budworm: Scouts in Decatur County reported increased TBW moth activity in cotton this week. It appears the second generation of TBW is starting. This is about 7-10 days earlier than during recent years.

Beet Armyworm: We continue to receive scattered reports of BAW infesting cotton. Only a few fields have required treatment, but we must be aware of the presence of beets.

Stink Bugs: During recent days we have received questions and comments regarding stink bugs in pre-bloom and blooming cotton. Stink bugs are considered a cotton pest when they feed on developing bolls. In prebloom cotton, stink bugs are feeding on the plant but we do not fully understand where they are feeding and if damage is occurring. We would expect stink bugs to feed on squares and/or new terminal growth. We would not expect economic damage in pre-bloom cotton unless populations are extremely high. Until we learn more, decisions to treat stink bugs on pre-bloom cotton should be based on square retention.

A portion of the crop has begun to bloom. Scouting for stink bugs should be initiated by the third week of bloom. At this stage of plant development, the older bolls are approaching the diameter of a quarter. Treatment decisions should be based on internal boll injury and/or stink bug counts.

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