Gray leaf spot is a common disease of tomato and pepper in warm, humid production areas such as the southeastern U.S. The disease can be caused by three different fungi of the genus Stemphylium, namely S. solani, S. floridanum, and S. botryosum f. sp. lycopersici. Infection often occurs in seedbeds or transplant houses when plants are very young. During warm, wet weather, spores of the gray leaf spot fungi germinate quickly in free moisture on the plant leaf and directly penetrate susceptible plants. The spores are dispersed readily by wind, but can also be spread by splashing rain and irrigation water. The gray leaf spot fungi survive pathogenically on alternate hosts such as gladiolas, solanaceous weeds, volunteer tomato, and in and on dead and decaying crop debris. The pathogens can survive long periods of time in crop debris.
Gray leaf spot symptoms are limited almost entirely to leaves, but when conditions are very favorable for disease, stem and petiole lesions can form. Disease symptoms are generally more prominent on tomato than pepper. Symptoms first appear as minute, circular to oblong, brownish black specks on lower leaves. Lesion are randomly scattered across leaves, and enlarge with age. Spots occasionally coalesce and kill large areas of the leaf. Spots later dry out and develop cracks before the entire leaf turns yellow. The infected leaf dies quickly and drops from the plant. Gray leaf spot does not affect fruit, but defoliation reduces fruit yield and grade.
No biological control strategies have been developed for gray leaf spot.
Plant high quality transplants free from gray leaf spot. Practice a three-year or longer crop rotation to nonhosts such as small grains. Eliminate crop debris, volunteers, and weeds that can serve as alternate hosts. Reduce periods of leaf wetness by avoiding overhead irrigation and dense plantings. Orientating rows parallel to the prevailing wind direction can promote rapid leaf drying and help reduce periods of extended leaf wetness. Many resistant varieties are available and should be planted if gray leaf spot is a recurrent problem.
Fungicide sprays effectively control gray leaf spot, but generally are not necessary in the High Plains; cultural control strategies alone are often necessary to manage gray leaf spot.
Product List for Gray Leaf Spot:
Pesticide |
Product per acre |
ApplicationFrequency
|
Remarks |
|
Captan |
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|
Captan 4F |
4 pt |
5-7 days |
4 day REI |
|
Captan 50 |
2 lb |
5-7 days |
4 day REI |
|
Chlorothalonil |
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|
Bravo 720, Ensign |
1.5-3 pt |
7-14 days |
Do not graze or feed debris to livestock; 7 day PHI |
|
Bravo Ultrex |
1.7-2.2 lb |
7-10 days |
Maximum of 18.3 pounds per season; 0 day PHI |
|
Bravo Weather Stik |
1.5-3.0 pt |
7-10 days |
Maximum of 20 pints per season; 0 day PHI |
|
Echo 720 |
1.5 -3.0 pt |
7-10 days |
Maximum of 2.5 gallons per season; 0 day PHI |
|
Echo 90DF |
1.7-2.5 lb |
7-14days |
Maximum of 16.67 pounds per season; 0 day PHI |
|
Echo Zn |
3-4 pt |
7-10 days |
Maximum of 3.6 gallons per season; 0 day PHI |
|
Ridomil/Bravo |
2-3lbs |
14 days |
Maximum of three applications; 14 day PHI |
|
Copper Fungicides |
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|
Champ Dry Prill |
1.33 lb |
5-7 days |
|
|
Champ Formula 2 |
1.33 pt |
5-7 days |
|
|
Copper-Count-N |
4-6 pt |
7 days |
|
|
Cuprofix MZ Disperss |
2.5-6 lb |
7-10 days |
|
|
Kocide 101 |
1.5-3 lbs |
5-7 days |
|
|
Kocide DF |
1.5-3 lbs |
5-7 days |
|
|
Kocide 4.5LF |
1-2 pts |
5-7 days |
|
|
Kocide 3000 |
0.75-1.75 lb |
5-10 days |
|
|
Nordox |
1.5-2.0 lb |
7-10 days |
|
|
Tri Basic Copper |
2-4 pt |
7-10 days |
1 day PHI |
|
EBDC, Copper/EBDC, and EBDC/Zoxamide |
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|
Cuprofix Disperss MZ |
1.75-4.75 lb |
3-10 days |
Maximum of 21 pounds per season; 5 day PHI |
|
Dithane DF |
2-3 lb |
7-10 days |
Maximum of 8.5 pounds per season; 5 day PHI; use a non-ionic surfactant to improve performance |
|
Gavel 75DF |
1.5-2.0 lb |
7-10 days |
Maximum of 4 (west of Rockies) to 8 (east of Rockies) applications per season; 5 day PHI; include a nonionic surfactant to improve performance |
|
Maneb 75 DF |
1.5-2.0 lb |
7-10 days |
Maximum of 8.0 pounds per season; 5 day PHI |
|
Manex 80W |
1.5-2.0 lb |
7-10 days |
Maximum of 7.5 pounds per season; 5 day PHI |
|
Manex |
1.2-2.4 qt |
7-10 days |
Maximum of 16.8 quarts per season; 5 day PHI |
|
ManKocide |
2.5-5.0 lb |
3-10 days |
Maximum of 42.7 pounds per season; 5 day PHI |
|
Manzate |
0.75-1.0 lb |
3-7 days |
Maximum of 8.5 lbs per season; 5 day PHI |
|
Penncozeb 80W |
1.5-2.0 lb |
7-10 days |
Maximum of 7.5 pounds per season; 5 day PHI. |
|
Penncozeb 75DF |
1.5-2.0 lb |
7-10 days |
Maximum of 8.0 pounds per season; 5 day PHI. |
|
Strobilurin and Strobilurin Mixtures |
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|
Cabrio |
8-12 oz |
7-21 days |
Maximum of 6 applications or 96 oz per season; Do not make more than 2 applications of Cabrio before alternating with a fungicide with a different mode of action; 0 day PHI |
|
Flint |
4 oz |
7-10 days |
Maximum of 4 applications or 16 ounces per season; Rotate with fungicides with a different mode of action such as Maneb or copper-containing products; 3 day PHI |
|
Quadris |
5-6.2 oz |
5-14 days |
Maximum of 5 applications or 1.15 quarts per season; Alternate Quadris with fungicides with different modes of action; 0 day PHI |
|
Tanos |
8 oz |
5-7 days |
Rotate and rotato with fungicides with a different mode of action such as chlorothalonil or mancozeb; Maximum of 72 ounces per season; 3 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: Eggplant, Pepper, Tomato, Disease, Gray Leaf Spot
Date: 04/01/2007