Many pathogens can cause damping-off and seedling blights of spinach in the High Plains region, including Pythium spp. and Rhizoctonia solani, and perhaps others such as Fusarium solani. 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 saphrophytically on crop residues. Pythium and Rhizoctonia are easily disseminated in irrigation water, contaminated soil on equipment, and movement of infected plant materials.
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 flaccid and die. Seedlings can be killed, but may survive and recover as plants develop.
Deny (Burkholderia cepacia) is registered for protection of roots from Fusarium, Rhizoctonia, and Pythium spp., but its efficacy in the High Plains is unknown.
Plant high quality seed in warm, well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Avoid excess irrigation and poor drainage. Planting into raised beds can help avoid water logging and promote rapid germination. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in damping off pathogens, but damping-off and seedling blight pathogens have very broad host ranges and can attack most plants.
Seed treatment with broad-spectrum fungicides is an economical and effective means of reducing disease, but a combination of two or more fungicides is often required to control the spectrum of damping-off and seedling blight pathogens. Chemical controls are most effective when integrated with sound cultural control practices.
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 |
In furrow at planting |
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. |
|
Fludioxonil |
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|
Maxim 4FS |
0.08-0.16 fl oz |
Seed treatment |
Suppression of Fusarium and Rhizoctonia spp. |
|
Metalaxyl/Methoxonam |
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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 pt |
Pre-plant incorporated soil drench or soil band (a 7” band is recommended) |
Suppression of Pythium and Phytophthora spp. |
|
Ridomil Gold GR |
20-40 lb |
Pre-plant incorporated soil drench or soil band (a 7” band is recommended) |
Suppression of Pythium and Phytophthora spp. |
|
Ultra Flourish |
2-4 pt |
Pre-plant incorporated drench or 7” soil band |
Suppression of Pythium and Phytophthora spp. |
|
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: Spinach, Diseases, Damping-Off, Seedling Blight
Date: 04/01/2007