To: Georgia Cotton Counties
Dear Co-Workers;
Cotton Situation:
The Georgia Weekly Weather and Crops Report for the week ending May 22nd listed the crop as 68 percent planted and 1 percent squaring. Dry soil conditions persist in many areas and have delayed planting.
Insect Situation: Thrips populations are moderate to heavy and infestations are being exacerbated due to limited soil moisture. Spotty infestations of cutworms, grasshoppers, and false chinch bugs are
also causing problems with stand establishment in conservation tillage fields. As cotton begins to square, scouts should begin monitoring of plant bugs and begin making square retention counts. Insects are looking for
moisture and we may see some additional strange occurrences if this pattern does not change.
Thrips:
Dry soil conditions are not conducive for uptake of systemic insecticides applied at planting for early season thrips control. In these situations, moderate to high thrips populations can cause some plant injury. Typical symptoms of thrips injury include the characteristic crinkling and cupping of leaves, stunting of plants, and in severe situations, abnormal branching of plants ("crazy cotton') and even stand loss. All fields should be monitored for thrips even if a preventive insecticide was used at planting. Foliar sprays are recommended if thrips number 2-3 per plant, especially if immature thrips are observed. The presence of immature thrips would suggest that our at-planting insecticide is not providing control. Immature thrips are light creme colored and lack wings compared with adults which may be black or yellowish-brown and have two pair of fringed wings. A hand lens will aid in separating adults and immature thrips. Damage from thrips is less likely to occur once seedlings reach the five leaf stage and are growing rapidly. Foliar treatments for thrips control include Orthene, Bidrin, and dimethoate. After a foliar spray, the next 1-2 leaves may continue to exhibit thrips damage symptoms since thrips were feeding on the terminal bud which contains unfurled leaves. Thrips damage appears to be slightly lower in conservation tillage compared with conventional tilled fields.
Cutworms:
We have received more reports of cutworm problems this year compared with previous years. The majority of infestations have occurred in conservation tillage fields. Richard McDaniel, CEC Burke County, reported severe damage in a field trial when cotton was planted into a legume cover. In general, the risk of cutworm attack is greatest following a legume cover crop as compared with following winter weeds or a rye or wheat cover crop. Risk is also increased for cutworm attack if green residue is present at planting. Cutworms are active at night and are either in the soil or under residue during the heat of the day. Due to the dry soil conditions, cutworm larvae may be more difficult to find. Larvae may be deeper in the soil than normal in search of soil moisture and a cooler habitat. If a stand is threatened, a recommended insecticide should be applied as soon as possible.
Grasshoppers:
Grasshopper populations are high in some strip-tillage fields. Potentially, grasshoppers can cut plants and the damage may resemble that of cutworms. We do not have much experience with grasshopper control in seedling cotton but have received reports of good control when pyrethroids were used. Orthene and Bidrin have also been reported to have good activity. Grasshoppers overwinter as eggs in the soil and a dry winter and spring favors their survival.
False Chinch Bugs: Like grasshoppers, false chinch bugs are generally associated with dry conditions. Extremely high populations are present in some fields, greater than 100 per square foot.
The most severe infestations have occurred in conservation tillage fields and on field borders. Adult false chinch bugs are slender, about 1/8 inch in length, and grayish with clear wings. Nymphs are brownish-gray in
color, scurry around quickly on the ground, and are more common in fields compared with adults at this time. False chinch bugs are sucking bugs and consume plant sap when feeding on the leaves and main stem. In severe
situations, stand loss may occur. No insecticides are labeled for false chinch bug control in cotton, but a high thrips rate of Bidrin, dimethoate, or Orthene should provide good suppression. Additionally, pyrethroids
or Lorsban used for cutworm control should also provide good suppression.
Cotton Scout Schools: There are still several scout schools scheduled around the state. They are as follows:
June 3, 2000 RDC
June 6 & 7, 2000 Jeff Davis Co.
June 8 & 9, 2000 Evans Co.
June 12, 2000 RDC
June 12 & 13, 2000 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" Click on "Cotton".
Sincerely,
