Phytophthora root and stem rot of safflower is caused by several fungus-like organisms in the genus Phytophthora, including P. cactorum, P. cryptogea, P. drechsleri, and P. nicotianae var. parasitica. These pathogens survive in infested crop residue and soil as dormant spores (oospores). Plants may be infected at all growth stages, but the disease is most severe with warm, wet soils, especially in fields irrigated by flooding. Water stress predisposes plants to infection.
Phytophthora root and stem rot symptoms appear first as a collapse of lower stems, which kills seedlings. On older plants, leaves become light green to yellow, wilt, and die. Infected roots are a reddish color, but become dark brown to black as disease progresses. Lower stems may also become dark brown or black as the disease progresses. Stem infections are much more damaging than root infections.
Biological control strategies have not been developed for Phytophthora root and stem rot.
Plant varieties with some degree of resistance to Phytophthora root and stem rot. Avoid planting safflower in poorly drained fields. Carefully manage irrigation water to avoid ponding; planting into raised beds can improve drainage near plant roots.
Seed treatment may provide some protection of seedlings from infection, but are most effective when combined with sound cultural practices.
Product List for Phytophora Root and Stem Rot:
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 |
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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: Safflower, Disease, Phytophora Root, Stem Rot
Date: 3/3/2005