Cotton Pest Management Newsletter #4
June 21, 2001

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending June 17th listed the crop as 99 percent planted, 29 percent squaring, and 4 percent setting bolls. Allison brought much needed rainfall to many areas of the state, but some areas remain dry. As a whole, we are off to a much better start in terms of moisture compared with previous years.

Insect Situation: Aphids numbers are beginning to build in various parts of the state. Tobacco budworm egg counts have decreased in most areas. Plant bugs and low square retention have been observed in isolated fields. Beneficial numbers look good.

Plant Bugs: Historically, Georgia has not had wide-spread problems with plant bugs. However, a percentage of fields will experience economic infestations and require treatment each year and thus all fields should be monitored for plant bugs. We have received reports of damaging populations of plant bugs and poor square retention from various parts of the state. If cotton is squaring, scouts should be making retention counts and be observant for plant bug activity. We recommend that scouts examine a single small square in the top of plants when making retention counts. But scouts must not ignore square set on other parts of the plant. Periodically, whole plants should be observed to verify fruit set on lower nodes. Ideally, we would like to retain greater than 80 percent of first position squares at first bloom. In fields where "blasted" or damaged small squares are observed or numerous missing positions are observed, it is important for scouts to be observant for tarnished plant bugs and cotton fleahoppers. The actual process of shedding damaged small squares is gradual, occurring over a few days. As an abscission layer forms, the square will become loosely attached to the plant and gradually become yellowish in color. In time, the damaged square will turn brown and even black before falling from the plant. In fields with poor retention, scouts should examine squares that are light yellow, or squares which fall from the plant when lightly touched, to determine the cause of shed. On pre-bloom cotton, recently damaged squares with no indication of worm damage would suggest that plant bugs could be the cause, especially if numerous plant bugs are observed. Potentially other stresses such as root damage from aggressive cultivation could cause loss of small squares. Several insecticides are recommended for plant bug control. One should choose treatments which are least disruptive to beneficial insects through insecticide selection or use of low rates. Growers should be especially cautious of disrupting beneficial insects on non-Bt cotton.

Tobacco Budworm: Tobacco budworm (TBW) egg counts have declined in most parts of the state. Only a small percentage of fields required treatment. We would anticipate TBW activity to increase as we approach July 4th.

Aphids: Aphid populations are becoming established in many areas of the state. Initial infestations begin when a winged female aphid infests a plant. She will give birth to living young (all cotton aphids are females) that will remain wingless. In about five days, the wingless females will also begin giving birth to live young. When the plant becomes crowded with aphids, adults will begin giving birth to aphids which will be winged as adults and thus be able to disperse to other areas of the field. In time, initial hot spots of aphids will spread to other areas of the field. In recent years, a small percentage of the acreage has required treatment, but most are able to endure the aphids until the naturally occurring fungus which normally occurs in early July causes populations to crash. The decision to treat aphids is difficult and must be made on a field by field basis. In general, one should consider the general health of the plant since aphids are an additional stress factor. Some symptoms of aphid feeding which may warrant treatment include: the presence of heavy honeydew and sooty mold, yellowing in the terminal or lower leaves, retention problems on drought stressed cotton, or limited growth on late planted cotton.

Scymnus Lady Beetle: Scymnus lady beetle larvae and adults have been observed during recent days. Most of us are probably familiar with the larval stage which is covered with white streamers of wax, but the adult is not as easily recognized. The adult Scymnus lady beetle is very small and dull orange to brown in color. One species has a black center line forming a "V" pattern on the wing covers. Scymnus larvae feed primarily on aphids but will also feed on eggs and small worms. It appears the wax covering on Scymnus larvae provides some protection from fire ants. As aphid populations build, fire ants will protect the aphids (farming honeydew) by removing aphid predators. However, Scymnus larvae are often numerous, sometimes the only predator observed, in aphid infested fields with high numbers of fire ants foraging on plants.

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