Powdery mildew is caused by the fungus Erysiphe polygoni, and can only infect sugarbeet. The disease occurs in most areas of the world where sugarbeets are grown. Conidia of the fungus, carried by wind, land on sugarbeet leaves and directly penetrate and infect the plant. Spore germination occurs optimally at 60ēC and high relative humidity, but can occur over a wide range of temperatures (60-86ēC) and relative humidity of 1 to100%. A whitish mat of fungal hyphae form and produce conidia that serve as a secondary inoculum source. The pathogen survives between sugarbeet crops on escaped, wild, and volunteer Beta spp. and perhaps as fungal overwintering structures (cleistothecia) in and on infected leaves. Sugarbeets produced in the southwest U.S. also may serve as an ovewintering source of the pathogen.
Mildew symptoms first appear as small, dispersed, whitish mats of fungal hyphae and conidia on older, lower leaves.
AQ10 biofungicide is registered for suppression of powdery mildew, but is not compatible with conventional fungicides.
Plant sugarbeet varieties less susceptible to powdery mildew.
Fungicides are often the only control strategy available for sugarbeet powdery mildew and should be applied at the first sign of disease and continued until the pre-harvest interval specified on the label. Fungicides applied for Cercospora leaf spot control may provide some control of powdery mildew.
Product List for Powdery Mildew:
Pesticide |
Product per Acre |
Application Frequency
|
Remarks |
|
Sulfur |
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|
Microthiol Special |
5-10 lb |
7-10 days |
0 day PHI |
|
Thiolux 80 |
10-20 lb |
7-10 days |
0 day PHI |
|
Strobilurin |
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|
Amistar |
3-5 oz |
5-14 days |
Maximum of four applications per season; rotate with a fungicide with a different mode of action; 0 day PHI |
|
Gem |
6-7 fl oz |
10-14 days |
Maximum of three applications per season; rotate with a fungicide with a different mode of action; 21 day PHI |
|
Headline |
9-12 fl oz |
5-14 days |
Maximum of four applications per season; no more than two sequential applications before rotating to a fungicide with a different mode of action; 7 day PHI |
|
Quadris |
9.2-15.4 fl oz |
5-14 days |
Maximum of four applications per season; rotate with a fungicide with a different mode of action; 0 day PHI |
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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: Sugarbeet, Diseases, Powdery Mildew
Date: 03/27/05