Cotton Seedling Disease Control
Seedling diseases of cotton cause serious losses to cotton producers in Mississippi each year. A Cotton Disease Council estimate shows Mississippi producers lose an average of 3 percent of their total crops to seedling diseases. The estimate does not include the cost of replanting.Seedling disease identifies a complex situation involving the interaction of several organisms and the environment. Certain fungi that cause these seedling diseases are carried either on or in the seed. Other fungi live from season to season in the soil and can attack the seed or seedling. The organisms that cause seedling disease are found in all cotton-producing areas of the United States, but populations differ from area to area. Soil-borne pathogens most commonly involved in the seedling disease complex in the Southeast are Rhizoctonia, Fusarium, and Pythium.
How To Identify Seedling Diseases
Seedling diseases may cause many different effects on cotton plants. These may be grouped into three general phases.Seed Rot
A number of organisms in the soil and on or in the seed can cause seed to rot. Seed decay can result from poor handling of seed during harvest or from poor storage conditions. Such seed tend to be low in ability to live and easy prey for seed-rotting organisms.Seedling Rot
Preemergent seedling rot describes the loss of a cotton seedling to disease between the time the seed germinates and emerges from the soil. The infection is usually seen as a soft rot or lesions on the expanding root and stem.Damping Off
Postemergence damping off is a phase of the disease occurring at any time during the first part of the growing season. "Soreshin" is another name for this stage of the disease.At first, plants are stunted and lighter green than normal. As the disease progresses, the plants begin to show midday wilting, and lesions appear near the soil line. These lesions are light brown at first but turn progressively darker until the whole area takes on a black "wire stem" appearance. These plants eventually die, leaving an uneven stand.
Control
Seed Treatments
All cotton seed used for planting should be treated with a fungicide. Seed-treatment fungicides are sold individually or in combinations of two fungicides under a single trade name. In combinations, one fungicide is active against Rhizoctonia, while the other is active against Pythium. Because several disease-causing organisms may be involved with seedling disease, the use of more than one seed-applied fungicide is suggested.The materials most commonly used in the Midsouth are Apron, Thiram, Vivatax-PCNB, RTU-Baytan/Thiram, Baytan 30, and Biological Fungicide Product-Kodiak Concentrate. Follow label directions closely.
Soil Treatments
1. Planter Box - Planter box is the least effective of the soil treatments, but it is better than no additional treatment. If equipment is not available for in-the-furrow fungicide applications, use a planter box treatment. Following are the most common materials used in the Midsouth:
| Planter Box Fungicides | Rates/100 lb seed |
| Delta Coat AD Prevail Kodiak HB Biological System 3 | 5.75 11.75
oz 8 16 oz 4 oz 12 oz |
Method of Application - Soil fungicides cannot be applied well by the hopper-box method with acid-delinted seed unless the seeds and fungicide are properly layered in planter box.
When mixed well with seed, some fungicide will fall out with each seed to treat the soil around it. Fungicides may reduce the seedling rate by 1020 percent, so you must calibrate the planter with the seed and fungicide mixture to get the desired seeding rate.
The hopper-box method is less expensive than in-furrow spray and in-furrow granules, but the method is also less effective. When used properly, the method gives better results than do seed treatments alone.
2. In-the-Furrow Granules - In-furrow granules have given about the same degree of seedling disease control as in-furrow spray applications. Granular fungicides that are recommended include the following:
| Fungicide | Drill rate/acre |
| Ridomil 5G* Ridomil Gold GR* Ridomil PC 11G Ridomil Gold PC Terraclor 10G** Terraclor 15G** Terraclor Super X12.5G Terraclor Super X18.8G Terraclor 6.5% plus Di-Syston 6.5% Terraclor Super X with Di-Syston Terraclor 6.5 with Thimet 6.5% | 1¼ 2½
lb 1¼ 2½ lb 7 10 lb 7 10 lb 8 15 lb 5 10 lb 8 12 lb 6 10 lb 12 15 lb 12 15 lb 15 lb |
| *For
broader spectrum disease control, apply with Terraclor
10G. **For broader spectrum disease control, apply with Ridomil 5G. | |
3. In-the-Furrow Sprays - In-furrow spray is considered the best way to apply soil fungicides and is recommended for use in fields with a history of seedling disease. The process mixes more fungicide with the soil to give a greater zone of protection around the germinating seed and young seedling.
For best results, apply the fungicide through two cone-type nozzle tips. Mount the front cone-type nozzle just behind the seed-drop outlet to treat the soil around the seed. Direct the rear nozzle to spray soil as it is tumbled into the seed furrow, with a small amount of spray striking the top of the covered row.
| Fungicide | Rate/acre |
| Demosan 65W Ridomil 2E* Ridomil 50W* Ridomil Gold EC* Ridomil Gold WSP Accu-Pak* Ridomil PC Liquid Twin-Pak Terraclor Super X EC Terraclor Super X plus Di-Syston EC Terraclor 2E | 2 3 lb in 10 20
gal water ¼ ½ pt in 5 15 gal water 1/8 1/4 lb in 5 15 gal water 1 2 oz in 5 15 gal water 1/16 1/8 lb in 5 15 gal water Use entire contents of container to treat 5 acres; apply in 5 15 gal of water/acre 3 6 pt in 5 15 gal water 4 5.5 pt in 5 15 gal water 3 6 pt in 5 15 gal water |
| *For broader spectrum disease control, mix with Terraclor 2E. | |
Remember that soil fungicides are used in addition to regular seed treatments, not in place of them. Treated seeds cannot be used for oil, food, or other purposes.
Summary of Seedling Diseases Control
Seedling diseases of cotton can be controlled only through the use of preventive measures. All of the control measures are taken before or at planting time.1. Cultural Control - A number of cultural practices lower the risk of seedling disease. Early cutting and shredding of stalks aid in the control of seedling disease by cutting down on the amount of inoculum that carries over from year to year. Also, it is important to prepare a good seedbed for seedling-disease control. Raised beds give some control to seedling disease, especially in early-planted cotton.
2. Soil pH - Maintain soil pH 6.0 to 6.5. Extremely low pH favors the development of some cotton seedling diseases. A pH of 6.0 to 6.5 not only encourages vigorous plant growth but also suppresses certain diseases.
3. Soil Temperature - Avoid planting when soil temperatures are below 68 °F. At this temperature, germination is slow and the seeds and seedlings are more vulnerable to infection.
4. Seed Quality - Poor-quality seeds with low germination rates are much more susceptible to seedling diseases than are high-quality seeds. Seeds with high germination usually produce more vigorous, healthy seedlings even under adverse conditions.
5. Seed Treatment - All cotton seeds used for planting should be treated with a fungicide. Seed-applied fungicide helps to prevent diseases caused by organisms carried on the seed surface and is the most important and economical method for controlling seed rot. Seed treatment is not a substitute for high-quality seed but is a supplement.
6. Soil Treatment - Soil fungicide is good insurance for getting a good stand of cotton. All producers should use at least a planter-box fungicide in addition to a seed treatment.
If the producer has a problem getting a stand (from seedling disease) one out of three years, an in-the-furrow granular or spray treatment would be economical.
The information given here is for educational purposes only. Reference
to commercial products or trade names is made with the understanding that
no discrimination is intended of other products that also may be suitable
and have label clearances. Always read and follow current label restrictions
on pesticide use.
By Dr. Frank Killebrew, Extension Plant Pathologist, Department of Entomology and Plant Pathology.
Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.
Publication 802
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of
Congress, May 8 and June 30, 1914. Ronald A. Brown, Director
Copyright by Mississippi State University. All rights reserved.
This document may be copied and distributed for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.
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