Cotton Pest Management Newsletter #1
May 24, 2001

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending May 20th listed the crop as 63 percent planted. Dry soil conditions have delayed planting in many areas. Cotton is being "dusted in" in parts of the state. Some areas received showers earlier this week.

Insect Situation: Thrips injury increased during the past week and foliar treatments have been needed on some fields planted in late April and early May. All fields should be checked for thrips injury, even if a preventive insecticide was used at planting. Isolated reports of grasshoppers and cutworms have been received. A few acres have required replanting due to one or both of these pests.

Thrips: Thrips populations and plant injury increased in the past week to ten days. In recent years, peak populations in cotton have appeared in late April and early May, but the big migration of thrips into cotton this season appears to have been delayed until recently. Thrips injury to seedlings has been compounded by dry soil conditions which are not conducive for uptake of preventive insecticides used at planting.

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: During recent years we have observed increased populations of grasshoppers 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. 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 may also occur on stands which are established. Recently several fields in Brooks County required replanting due to grasshopper damage. The stems of plants showed signs of feeding. Plants were not completely cut as we see with cutworm damage, but a portion of the stem had been chewed out. This damage weakened the plant which eventually died and/or broke over at the feeding site. This damage resembles cutworms and thus when troubleshooting, observations for cutworms should also be made. We have yet to gain much experience with grasshopper control, but pyrethroids appear to be our best treatment at this time.

Cutworms: We have received isolated reports of cutworm damage from various areas. Cutworm problems are more likely to appear in reduced tillage systems, but we have observed cutworm problems in some conventional tilled fields. Cutworms actively feed at night and during the heat of the day 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 after an insecticide application may help control.

Scout Schools:

May 29, 2001 Crisp, Dooly, Wilcox Cos.
May 31, 2001 Jeff Davis Co.
June 5, 2001 Evans Co.
June 18, 2001 Burke Co.

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