March 23, 1999

Seed Supplies Tight, Quality Down
Cutting Costs with Transgenic Seed
Early Season Thrips
Clarity Approved as a Burndown Treatment
Get the Most from Your Telone Application
Rich Baird Departs for Mississippi State

Seed Supplies Tight, Quality Down. (Brown) Many varieties--both transgenic and conventional--are in short supply. As a result, growers may have to settle for Asecond choice@ in terms of variety selection. We still have plenty of UGA Variety Trial Reports (hard copy) and the data may also be referenced on the web. There are also indications that the quality/vigor of some varieties may just meet the bottom quality standards in terms of warm/cool germination. There may be insufficient supplies for replanting. As a result, we need to make sure we get a stand the first time, which means that planting should be initiated only with favorable conditions. Soil moisture and temperature are the two most critical environmental factors. It is usually safe to proceed when temperature measured at a 4-inch depth at 9 a.m. reaches 65EF for 5 consecutive days.

Cutting Costs with Transgenic Seed. (Brown) The cost of transgenic cotton is now associated directly with the charges per bag. In terms of Bt, Roundup Ready, and Bt/Roundup Ready varieties, the cost for Georgia (except for a few counties in the northwestern corner) is based on a seed drop rate of 52,000 seed/A. The following chart translates 52,000 seed/A into seed/ft based on row spacing and technology costs based one seed/ft. Calculated average cost/seed/ft are based on charges for Bt @ $32/A, RR @ $9/A, and B/RR @ $41/A at a seeding rate of 52,000 seed/A.


Row spacing

52,000 seed/A equals ? seed/ft

Cost of technology based on 1 seed/ft ($/seed/ft)




36 inches

3.6 seed/ft




38 inches

3.8 seed/ft




40 inches

4.0 seed/ft





We have several studies addressing the issue of reduced seeding rates. These experiments were conducted in Plains and Tifton in 1995 to 1997 and involved the use of a Monosem planter to precisely deliver the desired number of seed/ft. The following chart summarizes these results.

While maximum yields were achieved with as few as 2 seed/ft (and a final stand ranging from 1.2 to 1.9 plants/f), it is probably ill-advised for most farmers to plant only 2 seed/ft unless conditions are near ideal and seed quality is good. However, these data and considerable field experience provide sufficient confidence for seeding rates in the 2.5 to 3.0 seed/ft range, which translate into considerable savings in transgenic technology costs. Reduced seeding rates are inappropriate if planting conditions are adverse (cool, wet weather; heavy residue), seed quality is marginal, or if precision planting equipment is unavailable..

Early Season Thrips. (Roberts) Thrips are an annual early season pest of cotton in Georgia. Adult thrips are tiny insects, about 1/16" in length with two pairs of fringed wings. They vary in color from yellowish to dark brown. Adults move into cotton fields from surrounding vegetation. Immature or larval thrips resemble the adults but lack wings. Damage occurs as thrips feed on young, unfurled leaves of seedling cotton. This causes the expanding leaf to become crinkled and distorted. Injury often results in stunted seedlings which may complicate post directed herbicide applications. Thrips injury may also cause reduced yields, delays in maturity, and in severe cases, stand loss.

Seedlings are most vulnerable to thrips attack from emergence to about the 5-leaf stage. If seedlings are not growing vigorously, the time or susceptible window to thrips injury is extended. Application of a preventive insecticide to control early season thrips is a recommended practice. Often these treatments will reduce thrips injury when plants are most susceptible. Once seedlings attain the 5-leaf stage and are growing rapidly, the likelihood of injury is reduced. All fields should be scouted, regardless of whether or not they are treated with a preventive systemic insecticide. At-planting treatments can occasionally fail to provide effective control when conditions are either too dry for uptake of the insecticide or too wet, resulting in the insecticide being leached below the root zone. The recommended threshold for thrips is 2-3 thrips per plant. Treatment is rarely needed once plants reach the 5-leaf stage and are growing rapidly.

A hand lens can aid in scouting for thrips and distinguishing between adult and larval thrips. The presence of winged adult thrips in a field treated with an at-planting insecticide is not necessarily an indication of insecticide failure. The adults may have only recently moved into the field and have not consumed a toxic dose of insecticide. However, finding high numbers of immature (wingless) thrips is cause for concern and treatment may be warranted if threshold levels are met. Generally, plant damage will also be visible if high numbers of immatures are present. Several foliar systemic insecticides are available for thrips control. After foliar treatments are applied, the next couple of leaves will continue to show thrips injury since the thrips were feeding on the unfurled leaves in the bud. Besides the added costs and nuisance of treating seedlings with foliar sprays for thrips, beneficial insects must also be considered. Typically, there are few beneficials found on seedling cotton, but there are some. Thrips sprays will reduce what beneficials are present which will be of value later in the season for suppressing beet armyworm and bollworms. Be sure to scout carefully and only treat if absolutely necessary.

Clarity Approved as a Burndown Treatment. (Brown) BASF recently received approval for Clarity as a burndown treatment in cotton. Clarity is basically a low-volatile dicamba product. The fit for Clarity is broadleaf weeds, and though there is limited local data or experience, it may improve control of cutleaf eveningprimrose and volunteer peanuts. Clarity has been used with success in the Mid-South for control of vines in stale seedbed production. The product has some residual activity and thus an interval of at least 3 weeks must occur between application and planting. Clarity should be used at a rate of 0.5 pt/A (or 8 oz/A) and can be mixed with Gramoxone or Roundup for broad spectrum control.

Get the Most From Your Telone Application. (Davis) Telone II, 1,3-dichloropropene, is currently a standard treatment in cotton fields with heavy nematode pressure. Applied correctly, Telone II provides significant economic benefit, but when applied incorrectly, nematode control is often disappointing. The two most common reasons for poor performance of Telone II in Georgia are improper calibration of equipment and application to soils that are too wet.

Proper calibration is critical for effective control. Applications below the recommended rate of 3 gal/A result in poor control. Excessive rates increase cost with little increase in control. Either calibration error can be Acostly,@ so it is well worth the effort to properly calibrate equipment. Telone II is very toxic and caustic, so calibration should be done with water to prevent human exposure. Because of differences in density between water and Telone II, a Acorrection factor@ in final calculations is necessary. County agents, crop consultants, dealers, and Dow AgroSciences Telone representatives can provide assistance in calibration.

Telone II is a fumigant and disperses in the soil through diffusion. Soil moisture greatly affects movement of the chemical in the soil. Under wet conditions, diffusion is poor and effectiveness is greatly reduced. To avoid this problem, do not apply Telone II to soils that are too wet. A rule of thumb is that soil conditions are right for Telone II application when temperature and moisture are right for seed germination. Do not try to compensate for poor soil conditions by increasing application rates. Apply fumigants when soil conditions are optimum rather than waiting until just prior to planting. Applications should be made at least 7 days prior to planting to prevent cotton injury.

Telone II should be placed at least 6 inches below seeding depth; 8 to 12 inches below the soil surface is typical. It is critical that plant rows be placed in the middle of the fumigated band or roots will quickly grow into untreated soil. A press wheel, roller, or other device must be used to close the furrow where Telone II is applied to prevent loss of the chemical into the atmosphere. Mounding soil into a bed directly over the shank trace also will seal the soil effectively. Sealing the soil surface to prevent volatilization into the atmosphere is difficult in soils that are too wet and increased losses result. If soil is too dry, the fumigant will volatilize into the atmosphere too quickly and efficacy will be reduced.

Rich Baird Departs for Mississippi State. (Brown) Dr. Rich Baird, Extension Plant Pathologist, has accepted a research/teaching position at Mississippi State University effective in April 1999. Rich has made important contributions in a number of areas. His comprehensive nematode survey program increased awareness regarding the intensity of nematode problems in many counties across the state, and he is among the leaders in the application of precision farming technology to nematode management. He has also done extensive work on the cotton black root problem. His position will not be immediately filled, but Dr. Richard Davis, Extension Nematologist located in Athens, will assume a more active role on the Extension Cotton Team with a focus on nematode management.

Steve M. Brown, Extension Agronomist-Cotton
Richard F. Davis, Extension Nematologist
Phillip Roberts, Extension Entomologist-Cotton