Cercospora leaf spot is caused by the fungua Cercospora betlicola. The disease cycle is initiated by conidia disseminated by wind and splashing rain and irrigation water. Conidia germinate when humidity is high or free moisture is available under high (77 to 95ºF) temperatures. The fungus sporulates optimally between 68 to 79°F and 90 to 100% relative humidity. The disease is highly influenced by weather conditions; plantings that mature in cool weather often escape severe infection. The fungus overwinters in infested seed and crop residues.
Cercospora leaf spot symptoms begin as small (0.1 to 0.2 inches in diameter), circular to angular, brown to dark green spots with a reddish brown margin form on older leaves. During periods of warm temperatures and high humidity or leaf wetness, tan necrotic spots on lower leaves will turn gray and lower quality or make the leaves unmarketable. The disease reduces spinach yield, quality, and marketability.
No biological control practices have been developed for Cercospora leaf spot.
Plant high quality spinach seed free from C. betlicola. Practice a three-year or longer rotation to nonhosts, such as small grains or corn. Avoid overhead irrigation, especially during humid, cloudy weather. Deeply bury crop residues soon after harvest to reduce pathogen survival and overwintering. Eliminate volunteer spinach, alternate hosts (mangel, red beet, Swiss chard, sugarbeet), and weeds (common lambsquarter, redroot pigweed, mallow, and bindweed) that can serve as Cercospora leaf spot inoculum sources. Reduce periods of leaf wetness by decreasing planting densities, orientating rows parallel to the prevailing wind direction, and avoiding overhead irrigation.
Chemical controls are most effective when integrated with sound cultural control practices. Copper-based fungicides may leave unattractive residues on leaves and make them unmarketable.
Product List for Cercospora Leaf Spot:
Pesticide |
Product per Acre |
Application Frequency (days) |
Remarks |
|
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 |
|
Neem |
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Trilogy |
2 pt |
7-14 days |
Maximum of 2 gallons per season; 0 day PHI |
|
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 |
|
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. 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: Spinach, Diseases, Cercospora Leaf Spot
Date: 04/01/2007