Cotton Pest Management Newsletter #3
June 13, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending June 9^th listed the crop as 97 percent planted and 27 percent squaring which is slightly ahead of the five year averages. As a whole, cotton is in fair to good condition, but some areas remain dry. As cotton enters bloom, moisture will become even more critical.

Insect Situation: Tobacco budworm numbers appeared to decrease this week in south Georgia. Beet armyworms continue to be observed in fields, but insecticide treatment has rarely been needed. Aphid numbers are building. Good populations of big-eyed bugs (higher than recent years) have been observed in squaring cotton.

Tobacco Budworm: Tobacco budworm (TBW) egg and worm counts decreased this week in southernmost Georgia. It appeared numbers were slightly higher than those observed in June during recent years. However, only a small percentage of non-Bt cotton required treatment with insecticide. TBW populations were also higher in tobacco this year compared to previous years. Development of TBW from egg to adult occurs in about 28-30 days. Thus, one would anticipate the second flight approximately 4 weeks following the initiation of the first. Typically the second generation of TBW will begin infesting cotton during late June or early July in southernmost areas and a few days later in more northern areas. However, scouts need to be alert for eggs and larvae at any time.

Beet Armyworm: Reports of beet armyworm (BAW) continue to be received. Although only a limited number of fields have required treatment with insecticide, we must be aware of the presence of BAW in a given area or field. Predators and parasites such as big-eyed bugs and Cotesia wasps are suppressing populations and conservation of natural controls will be important in coming weeks. BAW completes a generation in about 3 weeks.

Cotesia marginiventris: Cotesia is a small wasp about 1/8 inch in length which parasitizes most larval pests observed in cotton. Cotesia is particularly effective against beet armyworms. The white cocoons, containing Cotesia pupae, are commonly seen on cotton leaves. The adult wasp lays a single egg inside the host caterpillar. The egg will hatch in 1-2 days and the Cotesia grub will feed inside the caterpillar for about 6 days. The grub then bores out of the caterpillar, causing it to die, and spins a white cocoon which is about the size of a grain of rice. The adult wasps emerges from the cocoon in 4-5 days. A single wasp can parasitize 200-300 host caterpillars during its 10-14 day life. The developing grub can often be seen in the abdomen of developing BAW larvae. The abdomen of parasitized BAW will be yellowish in color. To confirm that the suspect BAW larvae has been parasitized, gently squeeze the larvae from the head towards the back. If the suspect larvae has been parasitized, the grub will be pushed out with the gut contents.

Plant Bugs: Tarnished plant bug numbers are low in fields which I have observed. However, scouts must be monitoring retention in all fields and should be observant for plant bug activity. Although plant bugs have historically not been a widespread problem in Georgia, there are individual fields which require treatment each year.

Aphids: Aphids can be observed at low levels in many fields. Often only small areas will be infested initially. In time, infestations will spread and infest the entire field.

Scout Schools: Several scout schools have been conducted to date. However there are still several programs scheduled in various parts of the state. Contact the coordinator at respective locations for more information.

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