White rust is caused by the fungus-like organism Albugo occidentalis. This pathogen is more closely related to downy mildew-type pathogens than the true rust pathogens. The source of the white rust pathogen that initiates epidemics is not known, but the pathogen is known to survive in infested crop debris as dormant resting structures (oospores) and, in milder climates, as mycelia and sporangia. Oospores are thought to disseminated by splashing rain and irrigation water, and possibly by blowing soil. In warmer climates, sporangia produced on weeds can be deposited onto spinach by wind, whereupon they germinate and produce a mobile spore called a zoospore. Zoospores penetrate plants through natural openings, eventually germinate, and form mycelia in spinach tissues. Disease is favored by cool to moderate temperatures (50 to 68ºC) and abundant rainfall.
Diseased spinach plants produce windblown sporangia that serve as secondary inoculum, infecting other plants and beginning the disease cycle again. Oospores eventually form in diseased tissue and overwinter in infested crop debris and the soil.
White rust symptoms initially appear as white, blister-like pustules on the lower surface of leaves. Opposite these pustules on the upper surface of the leaf may be a yellowish spot. The disease can reduce spinach yield, quality, and marketability.
No biological control strategies have been developed for white rust of spinach.
Practice a three-year or longer crop rotation to nonhosts with strict sanitation of weeds and volunteer spinach.
Chemical control strategies are most effective when integrated with sound cultural practices.
Product List for White Rust:
Pesticide |
Product per Acre |
Application Frequency (days) |
Remarks |
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|
Acibenzolar |
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Actigard 50WG |
0.5-0.75 oz |
7-10 days |
Maximum of 3 applications or 2.25 ounces per season; Do not apply to plants under stress or young seedlings; 7 day PHI |
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Copper Fungicides—not all formulations available are listed |
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|
Champ DP |
1.33-2.66 lb |
7-10 days |
Can cause leaf flecking |
|
|
Copper-Count-N |
3 pt |
7-10 days |
Can cause leaf flecking |
|
|
Cuprofix Disperss |
2.5-4 lb |
7-10 days |
Can cause leaf flecking |
|
|
Kocide 2000 |
1.5-2.25 lb |
7-10 days |
Can cause leaf flecking |
|
|
Kocide 3000 |
0.75-1.25 lb |
7-10 days |
Can cause leaf flecking |
|
|
Nordox |
2-3 lb |
7-10 days |
Can cause leaf flecking |
|
|
Nu-Cop 3L |
1.33-2.66 pt |
7-10 days |
Can cause leaf flecking |
|
|
Tri-Basic Copper |
4 pt |
7-10 days |
1 day PHI |
|
|
Fosetyl-Al |
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|
Aliette 80 |
2-5 lb |
7-21 days |
Maximum of 7 applications; 3 day PHI |
|
|
Mefoxonam |
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Ultra Flourish |
8 oz-4 pts |
Pre-plant incorporated drench or 7” soil band |
2 layby applications can be shanked in; 21 day PHI |
|
|
Ridomil Gold EC |
1-2 pt |
Pre-plant incorporated soil drench or soil band (a 7” band is recommended) |
|
|
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Ridomil Gold GR |
20-40 lb |
Pre-plant incorporated soil drench or soil band (a 7” band is recommended) |
|
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Ridomil Gold/Copper |
1 pack/2 acres |
14 days |
Maximum of 2 applications; 21 day PHI |
|
|
Neem |
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Trilogy |
2 pt |
7-14 days |
Maximum of 2 gallons per season; 0 day PHI |
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Potassium Bicarbonate |
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Armicarb 100 |
2.5-5 lb |
5-14 days |
Apply in at least 20 gallons per acre; 0 day PHI |
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Strobilurin |
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Amistar |
2-5 oz |
5-14 days |
Maximum of 4 applications; rotate with a fungicide with a different mode of action; 0 day PHI |
|
|
Quadris |
6.2-15.4 fl oz |
5-14 days |
Maximum of 4 applications; 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. Cri ticism 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: Spinach, Diseases, White Rust
Date: 04/01/2007