UGA Cotton Newsletter - March 21, 2000
Variety Selection for 2000
Cost Effective Nematode Management Starts Prior to Planting Cotton
Weed Control in No-Till or Strip-Till Cotton
Avoiding 2,4-D Injury to Cotton
Are Preemergence Herbicides Needed in Roundup Ready Cotton?
Summary of Roundup TVPTM Rewards Program
Dr. Bob Kemerait, Extension Plant Pathologist, Joins Cotton Team
Milan No-Till Field Day
Variety Selection for 2000. (Brown) Variety selection for this season has been confounded because of shortages of DP 458 B/RR and several RR varieties. The resulting predicament spreads considerable grief among growers, dealers, and the seed and technology companies. It makes choosing (and recommending) varieties difficult. While it is easy is to rant, stomp, and wring our hands, we have to deal with the situation and answer the question, "Where do we go from here?"...at least for the 2000 crop.
Option 1. Plant conventional varieties. Supplies and quality of several excellent conventional varieties are good. Competition abounds, and ultimately, that will improve variety offerings to producers in future years.
Option 2. Proceed with the purchase of DP 458 B/RR even though some lots have marginal cool test values. The problems of DP 458 B/RR have been well publicized and attributed primarily to dormancy. Specifically, quality problems have been reflected in marginal cool test numbers. Cool test values may improve over time as a result of conditioning, cool storage, etc. DeltaPine has indicated that some DP 458 seed with warm/cool test values that do not meet 80/60 but do meet 80/50 will be available but marked as such. Such seed should be planted only under near ideal conditions–when soil moisture is adequate for rapid germination and soil temperatures consistently exceed 70o F. Keep in mind that with technology varieties in short supply, we will NOT have sufficient seed to do a lot of replanting.
Option 3. Purchase alternative varieties with similar technology. The problem with this approach is that limited data and local experience exist regarding performance of these new varieties. Planting these continues the pattern of commitment to varieties with which we have not gained confidence and understanding. Full season stacked gene alternatives to DP 458 B/RR include DP 655 B/RR and PM 1560 B/RR. Data suggest that the latter may be the better of these two varieties. Several early to mid-maturity stacked gene varieties are available, including DP 451 B/RR, PM 1218 B/RR, SG 125 B/RR, SG 501 B/RR, and Stn 4892 B/R. Generally, the earlier varieties are more risky in south Georgia in the absence of irrigation. The following is an informal estimate of comeback potential (from greatest to least) based on limited knowledge and experience: DP 655 B/RR, PM 1560 B/RR, DP 458 B/RR > SG 501 B/RR, Stn 4892 B/R, DP 451 B/RR > PM 1218 B/RR, SG 125 B/RR.
Got Fertilizer ? (Harris) Like the milk commercial, this is a great question concerning basic plant nutrition. Cotton needs proper preplant fertilization and liming to get off to a good, healthy start. What should a young cotton crop be fed? The question is easily answered by soil testing. Sending in a soil sample is like going to the doctor, and in most cases, South Georgia soils need yearly "check ups." Below is a check list for providing good early season nutrition based on soil testing.
Soil pH - There have been some strange results with soil pH the last few years which are probably related to our erratic weather patterns (namely rainfall). The bottom line is, if the soil test calls for lime, you better have a good reason for not believing it and not liming. Yes, the dry weather may have caused some lime not to dissolve (especially bigger particles). But can you take a chance on not liming? Remember, aluminum toxicity can occur when pH drops below 5.5. Also, a ton (or half ton) of lime should not drive pH too high if pH is around 6.0 initially.
Phosphorous - This element needs to be put out preplant or with a starter since it is important to early (seedling) root growth. Since P is immobile in soil, it can be put out ahead of planting. Later applications, such as sidedressing, are not encouraged. Dribbling 10-34-0 close to the row soon after emergence is probably about as late as you want to apply P.
Potassium - Recent research indicates that applying most, if not all, of the recommended K "up front" (preplant or at planting) is better in terms of yield than split applications (½ at planting, ½ at sidedress). One exception to this would be on deep sands (especially irrigated), where some sidedress K may still be necessary. Preliminary research results also indicate that multiple foliar K sprays around peak bloom may be more efficient (and economical?) than sidedressing soil-applied K. However, foliar K is still not recommended across the board.
Nitrogen - This element is also key to getting the crop off to a good start. Waiting until after you get a stand or until sidedressing to apply your first N can be disastrous. The UGA recommendation is to apply 1/4 to 1/3 of the total N rate at planting. For example, if a typical N rate is 90 lb /a, then 30 lb N/a needs to be applied at planting. This is sometimes tricky when you are relying on starter fertilizer such as 10 gal/a of 10-34-0. Many growers "spike" 10-34-0 with liquid N solutions to get more preplant N. The only caution here is to keep the mixture out of the furrow to avoid "starter burn"
Calcium and Magnesium - If you are liming properly, and using dolomitic lime (as most growers do), then these elements should be in good supply. There have been some cases where pH is OK but calcium or magnesium is low. Gypsum for calcium and K-Mag for magnesium are good options here.
Manganese and Zinc - Availability of both of these micronutrients is dependent on pH. The higher the pH the more of these you need in soil. Deficiencies are likely to occur when pH is very high and soil test Mn or Zn are very low. These elements can be very expensive; therefore, if you have high pH/low Zn or Mn, consider SLOWLY building your Zn or Mn with small amounts (3 to 5 lb/A) of soil applied fertilizers. In the meantime, add these micronutrients to your starter fertilizer or foliar program. It is always best to double check or guide your decisions with tissue sampling around first square also.
Boron - Since boron is mobile in soil, foliar applications are still best. However, with Bt and stacked gene varieties, adding B in preplant, starter or sidedress fertilizers is more common. Even when using one of the alternative application methods, growers should also consider including B with other foliar sprays such as Pix or insecticides.
Sulfur - This one is easy to forget but can lead to trouble if neglected – especially with high N rates. The current UGA recommendation is for 10 lb S/A. An adjoining state recommends 20 lb/A. Sulfur can be applied either preplant or at sidedress. Keep in mind, S does not foliar feed very well.
Cost Effective Nematode Management Starts Prior to Planting Cotton. (Davis)
First, you need to estimate the nematode damage potential in each of your fields. This is usually based on a combination of two things: 1) a soil nematode assay to determine which nematodes are present and how many of each species are present, and 2) the field’s history of damage caused by nematodes. If you grew cotton in a field last year and you believe you suffered damage from nematodes, you should probably use a nematicide regardless of nematode assay results. In this situation, leave some strips without nematicide for comparison so you can judge if you were right in your assessment of the field’s damage potential (use something for thrips control in those strips or you can be misled). Current threshold levels for cotton are 100 southern root-knot, 80 Columbia lance, 250 reniform, or 1 sting nematode per 100 cm3 soil. Assume that root-knot nematodes found in samples from cotton or corn fields (even corn following peanuts!) are southern root-knot and will damage cotton. Assume that root-knot nematodes found in samples from peanut fields are peanut root-knot and will NOT damage cotton. At or above threshold levels, nematicide applications begin to increase yields enough to justify their expense. Below these levels, if yield increases following nematicide application occur at all, they usually will be relatively small so that the expense cannot be justified.
Second, when nematicide use is justified, you have to decide which nematicide to use and at what rates. If you choose to use Temik, use between 5 and 7 lbs/A in furrow. If you use less than 5 lbs/A you will get minimal nematode suppression. If you use more than 7 lbs/A in furrow, you will likely damage developing cotton seedlings thereby doing more harm than good. If you use Telone II, apply 3 gal/A at least one week prior to planting. The waiting period for Telone II is required by the label. If the seeds germinate before the chemical has dissipated from the soil, seedlings can be killed. If you use Telone II, you must use an additional chemical for thrips control. Telone II is likely to be most beneficial when damage potential from nematodes is high--if nematode levels are substantially above threshold or if a field has a history of significant damage.
And third, you have to calibrate your nematicide application equipment to maximize your chances for successful nematode management. If you put out too little nematicide, you will not get adequate control. If you put out too much nematicide, you are unlikely to significantly increase nematode suppression, but you will increase cost and the chances of damage to cotton seedlings with toxic chemical levels.
Weed Control in No-Till or Strip-Till Cotton (Culpepper, York). Cover crops (or heavy stands of winter weeds) should be killed at least two to three weeks before planting. This will avoid soil moisture depletion by the cover crop or weeds and allow time to apply additional burndown herbicide, if needed, to kill streaks that may have been missed during the original application. In general, you should kill a small grain cover crop after tillering but before the crop becomes too large to manage. Excessive cover crop residue can cause problems in the planting operation. If greater residue is desired, one can kill a strip over the row early and allow the cover crop in the row middles to continue to grow.
If no-tilling into natural cover (i.e., winter weeds), the need for an early burndown treatment will depend on the weed species present and the size of the weeds. An early burndown is normally advantageous, especially if ryegrass, cutleaf evening primrose, wild mustard, wild radish, or curly dock is present since smaller weeds are usually easier to control.
Cutleaf evening primrose has been one of the most common and difficult weeds to kill in strip-till or no-till fields. The most effective and economical option for cutleaf evening primrose is an application of 1 pint per acre of 2,4-D alone or mixed with Roundup or Touchdown at least 35 days before planting. Growers are strongly encouraged to incorporate this treatment into their no-till or strip-till management programs. Cutleaf evening primrose is very difficult to control in emerged cotton.
In addition to the burndown herbicide applied at least two weeks prior to planting, one may need to apply Gramoxone or Roundup at planting to kill any weeds emerging after the earlier burndown application.
Soil applied herbicide options for no-till or strip-till cotton are similar to those for conventional tilled cotton. One significant difference is the inability or limited ability to incorporate herbicides. In strip-till cotton, Prowl or trifluralin (Treflan, Trilin) can be incorporated into the tilled strip. If the herbicides are broadcast in strip-till or no-till systems, use Prowl instead of trifluralin.
See the 2000 Georgia Pest Control Handbook or speak with your local extension agent for specific herbicide uses and their rates to effectively manage weeds in no-till or strip-till cotton.
Avoiding 2,4-D Injury to Cotton (Culpepper, York) Cotton injury from 2,4-D continues to be a common and unnecessary problem. The problem can result from sprayer contamination, spray drift, and vapor drift.
Sprayer Contamination. Cotton injury can occur from minute residues of 2,4-D (or 2,4-DB) in a sprayer. It is recommended that any sprayer previously used to apply 2,4-D not be used in cotton. If such a sprayer must be used, it should be washed thoroughly before spraying cotton. Special attention should be given to sprayers used to apply Roundup Ultra or emulsifiable concentrates because these products seem to be particularly effective at pulling 2,4-D residues out of a sprayer.
The following procedure is suggested for washing out sprayers that have been used to apply
2,4-D. Keep in mind this procedure may not totally remove 2,4-D residues. Dispose of rinsates in an approved manner.
1. Remove nozzles, nozzle strainers, and in-line strainers. Using a soft brush, wash the nozzles and strainers with soapy water. Be sure to remove any visible deposits.
2. Before replacing nozzles and strainers, fill sprayer tank with water and add a strong detergent such as 4 pounds of trisodium phosphate per 50 gallons of water or a commercial spray tank cleaner. Agitate for 15 minutes and then flush about one-fourth of the water-detergent mixture through the lines. Replace nozzles and strainers and flush remainder of water-detergent mixture through the nozzles.
3. Spray diesel fuel on the inside surfaces of the tank. Start the sprayer to fill the lines, and let the diesel fuel sit in the lines for several hours, preferably overnight. Then spray out the diesel fuel. Note: this step is suggested only if the sprayer has previously been used to apply an ester formulation of 2,4-D.
4. Fill the tank with water and add household ammonia at the rate of 1 quart per 25 gallons of water. Agitate for 15 minutes, spray a few gallons of the mixture through the nozzles, and let the remainder sit in the tank and lines for several hours, preferably overnight. Then spray out the remainder of the ammonia-water mixture.
5. Fill the tank with water and detergent. Agitate for several minutes and spray it out.
6. Fill the tank with fresh water and spray it all through the nozzles.
Spray Drift. Spray drift means movement of spray droplets by wind. As opposed to vapor drift (described below), spray drift can occur with any formulation of 2,4-D (or any other product). Spraying during windy conditions and using nozzles and pressures that result in the creation of fine spray droplets increase the risk of spray drift.
Except in extreme cases, such as spraying in very windy conditions and using nozzles and pressures that create very fine droplets, spray drift normally is observed only over short distances. A buffer of 200 feet or more between the area being sprayed and the susceptible crop usually is adequate to prevent injury from spray droplet drift unless it is very windy. If there is no wind or if the wind is blowing away from the cotton field, a shorter buffer is acceptable.
Vapor Drift. Most cases of 2,4-D injury to cotton result from vapor drift of an ester-containing formulation of 2,4-D. Vapor drift results when the herbicide volatilizes and the vapors move to a susceptible crop such as cotton. Hot temperatures, moist soils, and thermal inversions all increase the potential for vapor drift. Injury from vapor drift can occur at rather long distances from the sprayed area.
Vapor drift can be avoided simply by refraining from the use of ester-containing formulations of 2,4-D. Ester formulations should not be used within a mile of any cotton field during the months that cotton is in the field. Most commercially available ester formulations are considered "low volatile." These formulations are still volatile, and their use can lead to cotton injury. Weedone 638 and any other formulations containing a mixture of 2,4-D ester and 2,4-D acid also should be avoided in cotton-producing areas. Vapor drift usually is not a problem with amine formulations of 2,4-D.
Ester and ester-acid formulations of 2,4-D are popular because they mix well with liquid nitrogen. Amine formulations also can be mixed with liquid nitrogen if the 2,4-D is premixed with water before adding it to the liquid nitrogen.
Are Preemergence Herbicides Needed in Roundup Ready Cotton? (Culpepper, York, Brown) Research has been conducted throughout the Southeast for several years to determine the value of soil-applied herbicides in Roundup Ready systems. With the exception of weeds difficult to control by Roundup (primarily Florida pusley and dayflower species), excellent weed control can be achieved with total postemergence systems that utilize Roundup and do not include soil-applied herbicides. However, in these studies, soil-applied herbicides increased cotton yields in two-thirds of the experiments if the initial Roundup application was delayed until the 3- to 4-leaf stage of cotton by avoiding early season weed competition.
These findings lead us to conclude that the primary value of soil-applied herbicides in a Roundup Ready system is the flexibility they bring in timing of Roundup applications. If there are weeds not controlled by Roundup, then soil-applied herbicides are recommended. However, elimination of soil-applied herbicides often necessitates two timely overtop applications of Roundup prior to the fifth leaf stage of cotton. For many growers, this is difficult to accomplish. Therefore, with proper soil-applied herbicides down, growers can delay the overtop Roundup application until the 3- to 4-leaf stage.
Summary of Roundup TVPTM Rewards Program. (Culpepper, Brown) Many agents, growers, and consultants have questions regarding Monsanto’s Roundup TVPTM Rewards program. According to literature by Monsanto, "The Roundup TVP Rewards program was designed to reward those growers who plant Monsanto technology crops for their loyalty to Roundup brand herbicides. Therefore, to be eligible for Roundup TVP Rewards, labeled Roundup brand herbicides are the only systemic, non-selective herbicides that may be used for burndown or in-crop applications on any Monsanto technology crop." It appears that only Roundup Ultra and Roundup UltraMax meet the requirements for this program in Roundup Ready cotton.
What is the benefit of the Roundup TVPTM Rewards program? Again, literature from Monsanto states the following: "If, within 60 days of planting, your qualifying Monsanto technology crop is destroyed for any reason, or fails to make an acceptable stand and is destroyed, you can receive a full refund of the technology fee paid for the seed used to plant lost crop acres. Lost crop acres do not have to be replanted to qualify." Qualifying Monsanto technology crops include Bollgard Cotton, Roundup Ready cotton, and Bollgard with Roundup Ready cotton.
Dr. Bob Kemerait, Extension Plant Pathologist, Joins Cotton Team. (Brown) Bob Kemerait, a recent graduate from the University of Florida, joined the UGA Plant Pathology faculty in Tifton on March 1. His responsibilities include Extension programs in cotton and peanuts. He can be reached at 912 / 386-7495 or We look forward to his contributions to Georgia agriculture.
Milan No-Till Field Day. (Brown) The Milan No-Till Field Day in Milan, Tennessee, is one of the best field days in all the South. It showcases the latest in conservation tillage equipment and technology. We have put together a tour/trip for the 2000 field day, which is on July 27. Attached is the schedule and registration form. Because of the limits of transportation (bus) and accommodations, participation is planned for 55, so interested folks need to reserve a spot soon. The tour is open to growers, county agents, industry personnel, and anyone interested in agriculture.
Prepared by:Steve M. Brown, Extension Agronomist-Cotton
20th ANNUAL MILAN NO-TILL FIELD DAY TOUR
JULY 26-28, 2000
The University of Georgia Cotton Team, with the assistance of the Tifton Campus Conference Office, is coordinating a three-day, two-night trip to the University of Tennessee Milan Experiment Station’s No-Till Field Day to view the latest equipment and technology pertaining to no-till crop production.
Tour package includes:Transportation. Round trip motorcoach transportation (departure/return Georgia National Fairgrounds and Agricenter, Perry, GA. Transportation will be in a 55 passenger coach equipped with air conditioner, restroom, and VCR. Secure parking is available.
20TH ANNUAL MILAN NO-TILL FIELD DAY TOUR
Name Social Security No.
In case of emergency, contact: Name____________________________Phone
Double Occupancy - $200 per person __________ Roommate
Single Occupancy - $295 per person ___________
Method of Payment: Check ______ Money Order/Traveler’s Check________
Credit Card: Visa____ MasterCard____ Discover____Card
Expiration Date_______________ Name on Card
Make check payable to Milan Tour/RDC and mail to: Milan No-Till Tour, Tifton Campus Conference Office, P.O. Box 1209, Tifton, GA 31793. If registering for more than one person be sure to include all the above information for each person.