Downy mildew of millet can be caused by two fungus-like organisms, namely Sclerospora graminicola, S. macrospora, and Plasmopara penniseti. S. graminicola and P. penniseti are known to occur in the U.S., but only P. penniseti is thought to be important on millet in the U.S. The downy mildew pathogens survive in the soil and infested crop debris as dormant spores (oospores) and mycelia and zoosporangia in seed. Oospores germinate during cool, wet weather in the spring and produce zoosporangia in which swimming zoospores are formed. Zoospores swim to plant roots, encyst, germinate, and form a germ tube that infects their plant host. The pathogens are disseminated by windblown sporangia, and the movement of infested seed and soil.
Downy mildew symptoms vary depending on the pathogen that causes them. Disease symptoms may appear as downy, white, fungal growth on the undersides of leaves; leaves are yellow opposite these infections. Plant stunting and leaf deformation often occur as plants grow.
No biological control strategies have been developed for downy mildew.
Crop rotation, sanitation of crop debris, and planting of pathogen-free seed may help to reduce downy mildew.
Seed should be routinely treated with a fungicide to reduce seed-borne contamination of the downy mildew pathogen.
Product List for Downey Mildew:
Pesticide |
Rate per 100 lb seed |
Application Frequency (days) |
Remarks |
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Captan—various formulations available |
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Captan 75 |
6-9 oz |
Seed treatment |
Broad spectrum, but weak against Pythium |
|
Fludioxonil |
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Maxim 4FS |
0.034-0.068 fl oz |
Seed treatment |
Suppression of Fusarium and Rhizoctonia spp. |
|
Metalaxyl/Mefenoxam |
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Apron XL LS |
0.32-0.64 fl oz |
Seed treatment |
Suppression of Pythium and Phytophthora spp. |
|
Allegiance-FL |
0.75-1.5 fl oz |
Seed treatment |
Suppression of Pythium and Phytophthora spp. |
|
Ridomil Gold EC |
0.25-1 pts |
Broadcast application |
Suppression of Pythium and Phytophthora spp. |
|
Thiram |
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42-S Thiram |
8 fl oz |
Seed treatment |
Broad spectrum |
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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: Millet, Disease, Downy Mildew
Date: 03/22/2005