HPIPM:Damping Off and Seedling Blight DB
From BugwoodWiki
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Author: Howard F. Schwartz, David H. Gent, Gary D. Franc and Robert M. Harveson
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Contents |
Identification and Life Cycle
Many pathogens can cause damping-off and seedling blight of dry bean in the High Plains region; primarily Pythium spp., but many other organisms are probably involved in damping-off. Damping-off is associated with cool 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 and pathogenically on alternate hosts and weeds. Damping-off pathogens are easily disseminated in irrigation water, contaminated soil on equipment, and movement of infected plant material.
Plant Response and Damage
Damping-off can occur before or after crop emergence. Pre-emergence damping-off results in a brown, gelatinous rotting within the seed coat. The radicle and cotyledons may become brown and soft after germination, but fails to emerge. Water-soaked, greasy lesions may also form on hypocotyls and roots after plant emergence when infected with Pythium spp., causing the plant to collapse and wilt. Plants can also wilt suddenly; and healthy-appearing plants can suddenly collapse during the heat of the day. After several days, plants permanently wilt. Seedlings can be killed, but may survive and recover as plants develop.
Management Approaches
Biological Control
Deny (Burkholderia cepacia) is registered for protection of roots from Fusarium, Rhizoctonia, and Pythium spp. T-22 Planter Box (Trichoderma harzianum strain KRL-AG2) is registered, but cannot by used in alkaline or cold soils. The efficacy of these biological control agents in the High Plains is not known.
Cultural Control
Plant high quality seed in warm (greater than 60°F), well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Avoid excessive irrigation and poor drainage. Planting into raised beds can help avoid water- logging and promote more 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. Conventional tillage tends to reduce damping-off as compared to minimum or no-till operations.
Chemical Control
Seed treatment with broad-spectrum fungicides is an economical and effective means of reducing disease, but is not a substitute for sound cultural practices.
Product List for Damping-Off and Seedling Blight:
| Pesticide | Rate per 100 lb seed | Application Frequency (days) | Remarks |
|---|---|---|---|
| Azoxystrobin | |||
| Amistar | 0.125-0.25 oz/1000 ft | Planting time treatment | Suppression of Rhizoctonia spp. |
| Quadris | 0.4-0.8 fl oz/1000 ft | Planting time treatment | Suppression of Rhizoctonia spp. |
| Captan | |||
| Captan 75 | 6-9 oz | Seed treatment | Broad spectrum, but weak against Pythium spp. |
| Captan 30-DD | 1.33-2.33 fl oz | Seed treatment | Broad spectrum, but weak against Pythium spp. |
| Captan 400 | 1.5-3.0 fl oz | Seed treatment | Broad spectrum, but weak against Pythium spp. |
| Captan 400-C | 1.5-3.0 fl oz | Seed treatment | Broad spectrum, but weak against Pythium spp. |
| Fludioxinil | |||
| Maxim 4FS | 0.08-0.16 fl oz | Seed treatment | Suppression of Fusarium and Rhizoctonia spp. |
| Metalaxyl/Mefenoxam | |||
| Apron XL LS | 0.085-0.64 fl oz | Seed treatment | Suppression of Pythium and Phytophthora spp. |
| Allegiance-FL | 0.75 fl oz | Seed treatment | Suppression of Pythium and Phytophthora spp. |
| Ridomil Gold EC | 0.5-2 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. |
| Thiram | |||
| 42-S Thiram | 4.5 fl oz | Seed treatment | Broad spectrum |
| Thiram 50WP | 4.5 oz | Seed treatment | Broad spectrum |
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.
