The fungus Rhizoctonia solani causes Rhizoctonia blight and stem canker. The pathogen survives in infected plant debris, and inoculum concentrations in the soil are increased by continually cropping fields to susceptible crops such as dry bean, potato and sugar beet. Rhizoctonia is spread within and between fields by irrigation water and soil movement. Rhizoctonia root rot of germinating seedlings is favored by moderate to high soil moisture and low soil temperatures. Damage is generally restricted to young seedlings, but can affect older plants, especially when the plants are stressed by extremes in temperature between warm soil and cool water from deep irrigation wells.
Rhizoctonia solani can cause seedling death, root and hypocotyl rot, and stem cankers. Initial symptoms appear on roots or hypocotyls as linear or circular reddish-brown sunken lesions or cankers delimited by a brown to reddish-brown margin. Rhizoctonia cankers enlarge with age, become darker, rough textured, and retard plant growth. The fungus can invade the central part of the lower stem and produce a brick-red discoloration. Disease symptoms often occur on scattered plants or in a somewhat circular field pattern. Severe seedling infection causes plant death. Rhizoctonia cankers enlarge with age, become darker, rough textured, and retard plant growth.
T-22 Planter Box (Trichoderma harzianum strain KRL-AG2) and Kodiak (Bacillus subtilis GBO3) are registered, but the efficacy of these biological control agents in the High Plains region are not known.
Plant high quality seed in warm, well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Select varieties less susceptible to Rhizoctonia blight and stem canker. Avoid excess irrigation and poor drainage. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in Rhizoctonia blight. Conventional tillage and incorporation of previous crop residues reduce Rhizoctonia blight.
Seed treatments may provide some disease suppression, but are most effective when combined with sound cultural practices.
Product List for Rhizoctonia Blight and Stem Canker:
Pesticide |
Rate per 100 lb seed |
Application Frequency (days) |
Remarks |
|
Captan |
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|
Captan 75 |
6-9 oz |
Seed treatment |
Broad spectrum, but weak against Pythium and Phytophthora spp. |
|
Captan 30-DD |
1.25 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium and Phytophthora spp. |
|
Captan 400 |
1-2 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium and Phytophthora spp. |
|
Captan 400-C |
1-2 fl oz |
Seed treatment |
Broad spectrum, but weak against Pythium and Phytophthora spp. |
|
Carboxin and Carboxin + Thiram |
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|
Vitavax 34 |
2 fl oz |
Seed treatment |
Suppression of Rhizoctonia |
|
Vitavax 200 |
4 fl oz |
Seed treatment |
Broad spectrum |
|
EBDC—several formulations available, but not all are listed |
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|
Dithane M45 |
2 oz |
Seed treatment |
Broad spectrum |
|
Fludioxonil |
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|
Maxim 4FS |
0.08-0.16 fl oz |
Seed treatment |
Suppression of Fusarium and Rhizoctonia spp. |
|
Thiram |
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|
42-S Thiram |
8 fl oz |
Seed treatment |
Broad spectrum |
|
Thiram 50WP |
8 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. |
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Categories: Safflower, Disease, Rhizoctonia Blight, Stem Canker
Date: 3/3/2005