Powdery mildew is caused by the fungus Erysiphe cichoracearum. The disease rarely occurs in the High Plains, and is only reported to cause economic damage to potato in Washington State under furrow irrigation.
Powdery mildew symptoms appear on leaves as white, powdery, circular to irregularly shaped patches. Mildew lesions are apparent on both sides of leaves as dusty, grayish brown deposits. Light brown flecks on stems and petioles often form, and large areas may become water-soaked with blackened spots. Lower leaves become yellow and then die, or may quickly blacken and then fall off. Internodes can become twisted and brittle. Plants can be killed.
No biological control practices have been developed for powdery mildew.
Powdery mildew is rarely a problem on potato grown under center pivot irrigation.
Fungicide applications for powdery mildew control are rarely needed in the High Plains.
Trade Name |
Product per Acre |
Application Frequency
|
Remarks |
Neem Oil |
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|
Trilogy |
1.0% in 25 to 100 gal per acre |
|
Maximum of 2 gallons per acre; cannot be tank-mixed with sulfur, Bravo, or other similar fungicides |
Strobilurins |
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|
Gem |
6-8 oz |
7- 14 days |
Maximum of six applications per season; Rotate with fungicides with a different mode of action; 14 day PHI |
|
Headline |
12 fl. oz |
7- 14 days |
Maximum of six applications per season; Rotate with fungicides with a different mode of action; 14 day PHI |
|
Quadris FL |
6.2 - 15.4 fl oz |
7- 14 days |
Maximum of six applications per season; Rotate with fungicides with a different mode of action; 14 day PHI |
Sulfur |
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|
Bravo S |
3-4 pt |
7-10 days |
|
|
Cavalry Sprayable Sulfur |
3-4 lb |
10-14 days |
|
|
Kumulus DF |
3-5 lb |
10-14 days |
|
|
Liquid Sulfur Six |
3-4 pt |
10-14 days |
|
|
Microfine Sulfur |
3-5 lb |
10-14 days |
Will also help control two-spotted mites. |
|
Microthiol Special |
5 lb |
10-14 days |
Will also help control two-spotted mites. |
|
Sulfur 6 Flowable |
3-4 pt |
10-14 days |
|
|
Sulfur 6L |
3-10 2/3 pt |
10-14 days |
Will also help control two-spotted mites. |
|
Sulfur Flowable 6 |
3-10 2/3 pt |
10-14 days |
Will also help control two-spotted mites. |
|
Terranil S |
3-4 pt |
7-10 days |
|
|
Wettable Sulfur |
5 lb |
10-14 days |
Will also help control two-spotted mites. |
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: Potato, Disease, Powdery Mildew
Date: 03/29/05