Cotton Pest Management Newsletter #1
May 16, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending May 12^th listed the crop as 57 percent planted. Dry soil conditions have delayed planting of dryland fields in some areas.

Insect Situation: Thrips populations are moderate to heavy and injury is being observed in some fields. All fields should be checked for thrips injury, even if a preventive insecticide was used at planting. Reports of grasshoppers and cutworms have been received and a few acres have required replanting due to one or both of these pests. A few isolated reports of beet armyworm have also been received.

Thrips: Thrips numbers are high in some areas. During most years, thrips injury appears to be greatest on cotton planted in April and early May. Thrips injury to seedlings has been compounded by dry soil conditions which are not conducive for uptake of preventive insecticides used at planting. Foliar sprays have been needed to supplement preventive treatments on some fields.

When dry soil conditions are present and high populations of thrips are present, plant injury may occur even if preventive insecticides were used at planting. Typical symptoms of thrips injury include the characteristic crinkling and cupping of expanding leaves, stunting of plants, and in severe situations, loss of apical dominance and even plant death. On cotyledon cotton, cotyledons with a silvery appearance are characteristic of high thrips populations and damage. At this time, all fields should be monitored for thrips and plant injury. Foliar sprays are recommended if thrips number 2-3 per plant, especially if immature or wingless thrips are observed. Immature thrips are a light creme color and lack wings compared with adults which may be black or yellowish-brown and have two pairs of fringed wings. A hand lens will aid in separating adults and immatures. Damage from thrips is less likely to occur once plants reach the 4-5 leaf stage and are growing rapidly. Foliar treatments for thrips control include Orthene, Bidrin, and dimethoate. After a foliar application is applied, the next 1-2 leaves may continue to exhibit thrips damage symptoms since thrips were feeding in the terminal bud which contains several unfurled leaves.

Grasshoppers: High populations of grasshoppers have been observed in some strip tillage fields. Grasshoppers are drought adapted pests and appear to be surviving by feeding on dead plant residues in conservation tillage fields. Dry winters, which we have been having, are conducive for survival and are one reason numbers are so nummerous. As cotton emerges, grasshoppers may feed on the first green plant tissues available in search of a more suitable food source and moisture. Observations have been made where grasshoppers have fed on the stem of seedlings during and just prior to emergence. Foliage feeding and some stem feeding may also occur on stands which are established. This damage resembles cutworms and thus when troubleshooting, observations for cutworms should also be made.

Insecticide treatment for grasshoppers should be based on plant feeding and if the stand is threatened. If extremely high populations are present at planting, a preventive spray may be justified. Immature or wingless grasshoppers are very susceptible to insecticide, but adults (winged) are difficult to control. If treatments are made, pyrethroids at a medium to high rate appear to be a good option.

Cutworms: We have received isolated reports of cutworm damage from various areas. Cutworm problems are more likely to appear in reduced tillage systems compared with conventional tilled fields. Cutworms actively feed at night. During the heat of the day, cutworms can be found in the soil or under cover crop residues. Control of cutworms is recommended if the stand is threatened. During very dry conditions, cutworms may not come up to the soil surface and thus avoid contact with broadcast insecticides. If irrigation is available, watering before an insecticide application may help control.

Beet Armyworm: Two isolated reports of treatable BAW infestations on seedling cotton were received from Colquitt and Tattnall counties. If beets are treated on seedling cotton, be sure to use a selective insecticide to conserved beneficial insects.

Scout Schools:

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