UGA Cotton Newsletter

July 28, 1999

Crop Condition
Boll Weevil Traps
Insect Scouting
Foliar Feeding Yellow Cotton
Residual Effects of Layby Cotton Herbicides
Forward Contracting
Black Root Survey Request

Crop Condition. (Brown) Rains since mid-June have resurrected a crop that was on the edge of disaster. Overall the crop has improved dramatically as indicated by the Georgia Agricultural Statistics Report from earlier this week.

Crop Conditions, Georgia and U.S., as of July 26, 1999 (%)

Very poor











U.S. crop






While much of the crop looks great from the road, there are wide differences in fruit set. There are also areas in which excess rain has drowned significant acreage. Early planted fields are moving rapidly toward cutout.

Boll Weevil Traps. (Roberts) Boll weevil traps should be installed on all fields at this time. If you have fields that are not trapped, please contact Boll Weevil Eradication Program personnel immediately (800 / 269-9931). Traps are critical in the detection of weevil reinfestation. In fact, traps are the primary means of finding weevils that come from weevil-infested areas or somehow reproduce in eradicated areas.

Additionally, traps are only functional when standing. If a trap is accidentally knocked down, please stand it back up.

Insect Scouting. (Roberts) To date insect pressure has been relatively light with the exception of a few localized areas. However, we need not become complacent as insect pressure in a particular field or area may change rapidly. Make sure scouts are in the field looking for pests. As we enter mid-July, we typically begin seeing migration of corn earworm from field corn and other hosts to cotton. In addition to searching the upper 12 inches of a plant for pests, a minimum of one bloom, one bloom-tagged boll (look on, in, and under the tag), and an additional boll lower in the plant canopy should be examined on each plant checked. Be observant for corn earworm eggs and larvae, fall armyworm, stinkbugs and damage, and other pests. On Bt cotton treatment is suggested if 7 to 8 corn earworm larvae 1/4 inch or greater in length are observed.

We are also receiving more reports of stinkbug damage. The risk of stinkbug attack is greater in unsprayed fields, or fields where insecticides that have activity on stinkbugs have not been applied (ie no pyrethroid sprays). Treatment for stinkbugs is suggested when stinkbugs exceed 1 per 6 row feet or internal damage to small bolls exceeds 20 percent and stinkbugs are observed. Internal stinkbug damage causes stained lint and/or warty growths on the inner surface of the boll wall. When sampling bolls for internal damage, nickel to quarter sized bolls should be randomly selected and examined internally for injury. Bolls of this age can be easily squashed in your hand and locks can be pulled exposing the inner surface of the boll wall. External symptoms of stinkbug damage include small sunken purple spots on the outer surface of bolls but are less reliable indicators of damage. Several pyrethroids, Bidrin, and methyl parathion are recommended for stinkbug control. During late July and early August it is common to observe corn earworm larvae in fields in addition to stinkbugs. In these situations, pyrethroids are preferred treatments due to their broader spectrum of activity.

Foliar Feeding Yellow Cotton. (Harris) Most areas of the state were dry for the first part of the growing season but now are receiving decent rains. Some are still dry. Some (believe it or not) are flooded out. These weather conditions (along with the fact that some growers went conservative on fertilizer rates due to the economic situation) have caused a lot of Georgia cotton to be yellow in color, especially in the top part of the plant. While this could simply be from rapid growth (especially where Pix is not used), it could also be nitrogen and/or potassium deficiency. Inadequate fertilization, leaching or runoff of fertilizer, and drought or waterlog stress can all cause these deficiencies. Soil type, rainfall pattern, previous fertilization, and growth stage of the cotton all need to be considered when making a decision to foliar feed cotton.

The best way to determine if yellowing is due to a nutrient deficiency is to petiole or tissue sample. Petiole sampling is the best since it is a comprehensive program that tracks N and K levels in the leaf stem over time as well as accounting for moisture conditions and fruit load. Troubleshooting or spot-checking with tissue and petiole samples can also be helpful since we know approximately where N and K levels should be at certain growth stages.

Some general rules of thumb to keep in mind when foliar feeding include: