May 26, 1999

Crop Conditions
Nutsedge Control Using Roundup Ultra and MSMA Tank Mixtures in Roundup Ready Cotton
Late Starter and Early Sidedress Fertilizer
Insect Hotline
Thrips Damage
Tobacco Budworm

Crop Conditions. (Brown) As of this week, we=re approaching 80 percent planted. Dry weather and replanting have hindered progress and thus we are behind schedule. Primary causes for replanting have been wind damage, moisture deficits, insect injury, seedling disease, and hail. In a few places, replanted acreage has exceeded 10 percent. Thrips have been heavy. Density and vigor of many stands are marginal.

The Boll Weevil Eradication Program released grower planting intentions May 21. Total anticipated acreage is 1,521, 287 (see attached map). Dry weather, financing, and seed availability may ultimately reduce that number.

Seed availability has compelled the planting of varieties that have never been planted in the state. We hope there are no surprises.

Replant decisions are often difficult. With prevailing drought and with each passing day, it becomes more difficult to destroy an existing though marginal stand especially in the absence of irrigation. Key factors include stand count, uniformity, and plant health. A stand that includes fairly uniform spacing and as few as 1 plant every 15 inches is probably adequate, assuming remaining plants have reasonable health, which means roots with little to no evidence of disease and emerging leaf tissues with good color.

Nutsedge Control Using Roundup Ultra and MSMA Tank Mixtures in Roundup Ready Cotton. (Culpepper) Nutsedge has been an especially troublesome weed in cotton this year. Due to the ability of nutsedge to reduce yield potential through competition, many growers have questioned whether mixing MSMA with Roundup Ultra in Roundup Ready cotton would increase nutsedge control. To date, this tank mixture is not labeled plus there is a slight potential that MSMA applied overtop of cotton can delay maturity and reduce yield. Additionally, the limited research available does not support the use of this tank mixture (Table 1). Culpepper and York reported no advantage of mixing MSMA with Roundup Ultra when Roundup Ultra was applied at 1.5 and 2.0 pints per acre. Because of the need for more research, experiments are being conducted by The University of Georgia=s cotton team to further study the effects of MSMA and Roundup Ultra combinations on nutsedge control.

Table 1. Percent nutsedge control with Roundup Ultra and MSMA tank mixtures.*


Yellow Nutsedge

Purple Nutsedge




1.0 pts/acre


1.0 pts/acre

% Control

Roundup Ultra






Roundup Ultra

1.5 pts/acre





Roundup Ultra

2.0 pts/acre





*Data supplied by Stanley Culpepper and Alan York from the Crop Science Department at North Carolina State University. This experiment was conducted only once in 1998 and growing conditions were ideal.

Late Starter and Early Sidedress Fertilizer. (Harris) The dry weather has delayed planting in some areas, while in others it will soon be time to sidedress. Starter fertilizers at this time of year, and especially in conventional tillage systems, are not likely to do much good. Starter fertilizers may still be considered in conservation-tillage, low phosphorous soils or where the nitrogen is counted on for the Aup front@ portion of the total N rate. Soil temperatures are good. Water is the most likely limiting factor for early growth this year.

The normal window for sidedress N applications is between first square and first bloom. Hedge toward first square on dryland or where preplant N is playing out (determined either visually or by tissue sampling). In irrigated fields in color (green!) is good. It is inadvisable to push growth on dryland fields with large doses of early sidedress N. Again, water is the limiting factor in most cases right now. Excessive sidedress N in this situation could unnecessarily add to cost if it doesn=t rain or interfere with the vegetative/reproductive balance if it does rain. Consider going a little more conservative with the sidedress N rate on dryland and plan on making up the difference with foliar N if yield potential holds up.

There are many, good sidedress N fertilizers available. Ammonium nitrate (solid) and liquid N solutions will make up the bulk of straight N materials. Adding ammonium sulfate to solid blends or ammonium thiosulfate to liquid N solutions will provide sulfur if needed. Boron can also be included in solid or liquid sidedress materials. Adding potassium with sidedress N may not be as critical as once thought, especially if an adequate amount of potash was applied preplant. Potassium can still be used in sidedress but should probably not make up more than half of the recommended rate. Foliar K applications (potassium nitrate) around first bloom may be as effective as sidedressing with K. Consider using some foliar K on deep sands or under high-yield conditions.

Insect Hotline. (Roberts) Cotton insect updates can be accessed with a toll free call at 1-800-851-2847. Updates on the current insect situation and management are made at least weekly and more frequently if needed. Comments and observations of insect conditions in your area are welcomed to assist in updating the tapes. In addition to cotton, information on peanut and pecan insects can also be accessed at the same number.

Thrips Damage. (Roberts) Thrips numbers have been fairly high in many parts of the state. Damage to young terminal growth has been reported from many fields. In some situations dry soil conditions have further complicated thrips problems due to the difficulty of uptaking in-furrow insecticides. Foliar treatments for thrips are recommended when 2-3 thrips per plant are counted, especially if high numbers of immature or wingless thrips are observed. Once plants reach the 5-leaf stage and plants are growing vigorously, treatment is rarely necessary. Generally thrips problems become less severe as we enter June, due in part to more favorable temperatures for rapid seedling development.

Tobacco Budworm. (Roberts) We typically expect to observe the first tobacco budworm flight in early June. In most years these populations are more prevalent on older squaring cotton. It appears only a small percentage of cotton will be squaring by early June, but scouting all cotton would be recommended. On non-Bt cotton, the recommended treatment threshold is 7-8 larvae per 100 plants prior to the first spray. As producers have gained experience, many have raised their June tobacco budworm threshold when beneficial insects populations are high. If treatment is needed, it would be advisable to use a selective insecticide that will maintain beneficials in the field.


Cotton Scout Schools
May 29, Johnson/Laurens Counties
June 5, Tifton (Rural Development Center)
June 14, Tifton (Rural Development Center)

3rd Annual Precision Agriculture Conference, June 2-3, RDC in Tifton
contact Craig Kvien)

Deep South Weed Tour, June 29-July 1 - (contact SM Brown)
8:00 a.m. (CST) Wednesday, June 30 @ Headland, AL
10:00 a.m. (EST) Thursday, July 1 @ Plains, GA, Southwest Branch Station
1:00 p.m. (EST) Thursday, July 1 @ Tifton, GA, Ponder Farm

Southern Conservation Tillage Conference, Tifton, July 6-8 - (contact John Baldwin)

CSRA Conservation Tillage Field Day, Waynesboro, July 15 - (contact Richard McDaniel)

SunBelt Ag Expo Field Day, Moultrie, July 20 - (contact Mike Bader)

Milan No-Till Field Day, July 22 in Milan, TN

Prepared by:
Steve M. Brown, Extension Agronomist-Cotton
A. Stanley Culpepper, Extension Agronomist-Weeds
Glen H. Harris, Extension Agronomist- Soils and Fertilizer
Phillip Roberts, Extension Entomologist-Cotton