Damping-off is caused by a complex of fungi, including Rhizoctonia solani and Pythium spp. Damping-off is associated with cool to warm soil temperatures, excess soil moisture, and delayed seedling emergence. Pathogens associated with damping-off are common soil inhabitants and can survive in soil as dormant oospores or sclerotia, pathogenically on alternate hosts and weeds, and saprophytically on crop residues.
Damping-off can occur before or after crop emergence. Pre-emergence damping-off results in a brown, gelatinous rotting within the seed coat. Radicles and cotyledons may become brown and soft after germination, but fail to emerge. Water-soaked, greasy lesions may also form on hypocotyls and roots after emergence when infected with Pythium spp., causing plants to collapse and wither. Post-emergence damping-off caused by R. solani begins as elliptically-shaped, brown to black sunken cankers on roots and hypocotyls with a sharp margin between infected and healthy tissue. Plants can become girdled and die, but lightly infected roots often survive and produce nearly normal roots.
Kodiak (Bacillus subtilis strain GBO3) is registered for protection of roots from Pythium and Fusarium spp., but its efficacy in the High Plains is unknown.
Encourage rapid seed germination and vigorous growth of seedlings by planting high quality seed in warm, well-prepared seedbeds. Avoid planting into cold soils, excessive irrigation, poor drainage, and compaction. Ensure crop residues from the previous crop are thoroughly decomposed before planting. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in damping-off pathogens, but some damping-off and seedling blight pathogens have very broad host ranges and can attack most plants.
Fungicides are most effective when two different seed treatments are used in combination with cultural control strategies.
Product List for Damping-Off and Seedling Blight:
Pesticide |
Rate per 100 lb seed |
Application Frequency (days) |
Remarks |
|
Azoxystrobin |
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Quadris |
0.4-0.8 fl oz/1000 ft |
In-furrow spray |
Suppression of Rhizoctonia spp. |
|
Captan |
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|
Captan 75 |
6-9 oz |
Seed treatment |
Broad spectrum, but weak against Pythium spp. |
|
Captan 30-DD |
1.25 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium spp. |
|
Captan 400 |
1-2 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium spp. |
|
Captan 400-C |
1-2 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium spp. |
|
Fludioxinil |
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|
Maxim 4FS |
0.08-0.16 fl oz |
Seed treatment |
Suppression of Fusarium and Rhizoctonia spp. |
|
Metalaxyl/Mefenoxam |
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|
Apron XL LS |
0.085-0.64 fl oz |
Seed treatment |
Suppression of Pythium and Phytophthora spp. |
|
Allegiance-FL |
0.75-1.50 fl oz |
Seed treatment |
Suppression of Pythium and Phytophthora spp. |
|
Ridomil Gold EC |
1-2 pts |
Pre-plant incorporated soil drench or soil band (a 7” band is recommended) |
Suppression of Pythium and Phytophthora spp. |
|
Ultra Flourish |
2-4 pts |
Pre-plant incorporated drench or 7” soil band |
Suppression of Pythium and Phytophthora spp. |
|
PCNB |
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|
Terraclor 15G |
125 lb |
Planting time drench |
Broadcast or apply in band or seed |
|
Terraclor 75%WP |
15-20 lb |
Planting time drench |
Broadcast or apply in band or seed |
|
Terraclor Flowable |
1.9-3.8 gal |
Planting time drench |
Broadcast or apply in band or seed |
|
Thiram |
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|
42-S Thiram |
8 fl oz |
Seed treatment |
Broad spectrum |
|
Thiram 50WP |
8 oz |
Seed treatment |
Broad spectrum |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Cole Crops, Disease, Damping Off, Seedling Blight
Date: 04/01/2007