Cercospora Leaf Spot and Berry Blotch of Coffee
Cercospora leaf spot (also known as brown eyespot) and berry blotch are two phases of a common disease caused by a plant-pathogenic fungus in Hawaii. The disease(s) may be economically important at some locations or in some seasons due to the costs associated with managing the disease and to the damaging effects upon plant growth, coffee yield and quality.
Disease name(s): in English: Cercospora leaf spot (leaves); brown eye spot (leaves); berry blotch (berries and cherries)
; in Spanish: mancha ocular del cafeto; mancha de hierro.
Host (common name): coffee
Host (scientific name): Coffea arabica L. (Arabica coffee); Coffea spp. Coffea L. is a genus of about 40 species.
Plant family: Coffee family (Rubiacea).
Description of plant: Coffea arabica is a shrub or small tree grown for its beverage-yielding seeds. Leaves are shiny, oval, pointed, 3-6 inches long. Flowers are white, fragrant and massed in thick clusters at leaf axils along the wide-spreading branches.
Geographic range of plant: Coffea L. originates from the Old World tropics, especially Africa. Coffea arabica is a native of tropical Africa and is now cultivated throughout the tropics and grows wild on a number of islands in the Pacific.
Pathogen (fungus): Cercospora coffeicola Berk. & Cooke; distributed throughout the tropics and Hawaii. There is morphological variation among Cercospora isolates from coffee in Hawaii.
The fungus: Fruiting is amphigenous, mostly on the upper leaf surface. Stromata are slight to 50 μm diam, globular, dark brown. Conidiophores are in fascicles, 3 - 30 stalks, pale to medium brown, sometimes branched, septate, mildly to abruptly geniculate, 20 - 275 x 4 - 6 μm. Conidial scars are distinct, thickened. Conidia are hyaline, acicular to obclavate, nearly straight, apex acute, base truncate or subtruncate with conspicuous thickened hilum, indistinct multiseptate, 40 - 150 x 2 - 4 (-7) μm.
Sites of infection: leaves; fruits.
Pathogen dispersal: Spores (conidia) are windborne (mostly during the daytime) and are also dispersed by splashing rain and by human contact and movement or workers and machinery within coffee fields and nurseries.
Environmental conditions favoring disease development: The highest risk for infection occurs approximately between the temperature range of 20°- 28°C (68°- 82.4° F) and between about 36 to 72 hours of continuous leaf or berry wetness.
Predisposing factors: (1) poor plant nutrition (low leaf nitrogen and potassium); (2) general plant stress (drought, sun exposure, poor fertilizer management, or excessive weed competition); (3) insufficient shade; (4) glyphosate (herbicide) injury; (5) poor soil or growth medium; (6) root disease (e.g., coffee nematode decline caused by root-knot nematodes, Rhizoctonia root rot).
Disease symptoms and signs:
(1) On Leaves - the classic symptom is circular spots with tan, gray or white centers; lesions may be irregular in shape and cause leaf blight. Lesions begin as small, chlorotic spots that expand to become deep brown on the upper leaf surface. The centers of leaf spots turn grayish-white, and are encircled by a distinct ring (0.2 - 0.6 inches diameter) of brown-colored tissue. The margins of lesions are dark brown to reddish brown or purplish to black in color. Lesions are sometimes surrounded or ringed by a bright yellowish "halo" which is more visibly apparent on the upper leaf surface. Dark-colored and silvery-colored sporulation (conidia) of the pathogen, Cercospora coffeicola, may be visible to the naked eye within the grayish-white centers of lesions. Affected leaves may defoliate prematurely.
Typical "brown eyespots" is a diagnostic symptom of the disease (above).
New re-growth after pruning (left) is susceptible to infection. At high, cloudy and wet altidues (>2,000 ft.) in Hawaii, leaf spots may become leaf blights, causing more damage (right).
(2) On green berries - lesions are initially brown in color, sunken, longitudinal or irregular or oval in shape, with ashy centers, rarely 0.2 inches long and sometimes encircled by a purplish halo (the halo is tissue which ripens prematurely due to the infection). Infections can occur at any stage of berry development.
(3) On red cherries - large, sunken, blackened areas develop which may be covered with a silvery sheen of fungal spores. Infections that penetrate to the seed may cause the pulp to adhere to the parchment during processing. Diseased cherries may be subject to attack and further degradation by opportunistic bacteria or fungi such as Colletotrichum gloeosporioides (a ubiquitous fungus that causes anthracnose on many crops). The conspicuous presence of C. gloeosporiodes as an opportunist and secondary invader of cherries damaged first by C. coffeicola can confuse the disease diagnosis. As a result, in Hawaii some coffee farmers refer to this disease erroneously as "anthracnose."
Crop damage:
(1) Damage to cherries and seeds (beans) - when disease is severe, there is general crop loss (yield reduction, berry shriveling, premature berry drop, premature ripening, reduced coffee grade). Coffee beans may be stained or off-grade and parts of the cherry pulp may adhere to the parchment, resulting in difficulty in coffee milling, discolored parchment and beans, and a sour taste of the processed beans.
(2) Damage to leaves - defoliation; reduced photosynthetic leaf area; loss of vigor.
Integrated pest management practices (IPM) for Cercospora leaf spot and berry blotch:
- maintain adequate plant nutrition (coffee plants suffering from elemental deficiencies such as nitrogen and potassium are more susceptible to this disease). In fact, the disease may be effectively prevented or controlled in most locations with a proper fertility regime;
- perform periodic coffee plant tissue analysis and soil testing to determine the appropriate fertilizer regime; this can be based upon UH-CTAHR Agricultural Diagnostic Service Center (ADSC) recommendations;
- sanitation and crop debris management (after pruning, remove crop debris from field, do not pile it up against the plants in the field; leaf and berry debris can harbor the pathogen and initiate further cycles of disease);
- choice of planting location (avoid very high elevations and rainy locations) and orientation of rows (where rows are perpendicular to prevailing winds, plant canopies and leaves become dry more quickly);
- select a reasonable planting density (number of plants per acre);
- intercrop coffee with non-Coffea sp. (other species are not susceptible to the disease);
- strive to minimize plant stresses (stresses such as drought, under-nutrition, planting on impermeable rock outcroppings, root-knot nematodes, and root rot predispose plants to infection);
- provide or ensure adequate soil drainage (this minimizes root rot);
- grow coffee under shade (35% to 65%), or in an agroforestry setting;
- avoid over-irrigation (this will minimize plant stresses such as root rot and will reduce relative humidity within the plant canopy);
- avoid working with coffee plants and moving through fields and nurseries when diseased plants are wet (this minimizes potential dispersal of fungal conidia within and among plants);
- prune coffee trees to increase air circulation in the canopy;
- harvest cherries on time, before disease progresses too far;
- avoid injuring coffee plants with herbicides, especially glyphosate (plants injured by this herbicide may be more susceptible to infection);
- control weeds (this minimizes plant stress and relative humidity in the plant canopy);
- apply fungicide sprays to foliage where environmental conditions are particularly conducive to infection and disease development (please refer to Fungicide Recommendations below);
- avoid planting coffee too deep;
- protect new coffee foliage re-growth after pruning with fungicide sprays (immature leaves are more susceptible to infection than mature leaves).
Fungicide recommendations: In Hawaii, copper fungicides are normally used, such as Kocide products (see table below). It is important to protect the fruits from the leaf phase of the disease. For Kocide 101 products, use from 1.5 to 6 lbs. of product per acre in 50 to 100 gallons of water. Add a spray adjuvant or "spreader/sticker" product such as the organosilicate Tactic™ (1% v/v) to enhance coverage and product adhesion to foliage. Sprays should coincide with dry weather and calm winds. Three spray applications per season should suffice (occurring approximately once per month), beginning at flowering. Thorough coverage of the plant canopy is very important. Large farms in Hawaii utilize tractor-mounted mist blowers. Always refer to the fungicide label(s) for instructions and personal protective equipment and proper site of application (for example, copper fungicides should be applied to leaves, and not to roots).
Table 1. Some Fungicides Registered for Coffee in Hawaii (2008) for control of Cercospora diseases (source: Hawaii Pesticide Information Retrieval System; always consult the product's label before using the product).
|
Product Name |
Active Ingredient |
Formulation* |
|
Champ Formula 2 Flowable Agricultural Fungicide/Bactericide |
Copper hydroxide (37.5%) |
FC |
|
Champion Wettable Powder Agricultural Fungicide |
Copper hydroxide (77%) |
WP |
|
Champion WG Agricultural Fungicide |
Copper hydroxide (77%) |
WP |
|
DuPont Kocide 101 Fungicide/Bactericide |
Copper hydroxide (77%) |
WP |
|
DuPont Kocide 2000 Fungicide/Bactericide |
Copper hydroxide (53.8%) |
WDG |
|
DuPont Kocide 4.5 LF Fungicide/Bactericide |
Copper hydroxide (53.8%) |
WDG |
|
DuPont Kocide DF Fungicide/Bactericide |
Copper hydroxide (61.4%) |
WDG |
|
Griffin Kocide 2000 Fungicide/Bactericide,
Griffin Kocide 2000 T/N/O Fungicide/Bactericide |
Copper hydroxide (53.8%) |
WDG |
|
Griffin Kocide DF Dry Flowable Fungicide/Bactericide |
Copper hydroxide (61.4%) |
WDG |
|
Griffin Kocide 101 Fungicide Wettable Powder |
Copper hydroxide (77%) |
WP |
|
Griffin Kocide LF Fungicide/Bactericide |
Copper hydroxide (23%) |
EC |
|
Griffin Kocide 4.5 LF Fungicide/Bactericide |
Copper hydroxide (37.5%) |
FC |
|
Nu-Cop 50WP |
Copper hydroxide (77%) |
WP |
|
Nu-Cop 50 HB |
Copper hydroxide (77%) |
EC |
|
Nu-Cop 50 DF |
Copper hydroxide (77%) |
WDG |
|
Monterey Liqui-Cop Copper Fungicidal Garden Spray |
Tetraaminecopper (31.4%) |
EC |
*EC = Emulsifiable concentrate; WP = Wettable powder; WDG = Water dispersible granules; FC = Flowable concentrate
General disease notes: (1) Symptoms of Cercospora berry blotch disease may be confused with a condition of coffee referred to as "overbearing dieback;" (2) The yellow halo around lesions is caused by a toxin produced by Cercospora species, known as cercosporin; (3) Premature ripening of infected berries and cherries occurs due to ethylene gas emission during the disease process. Ethylene is a plant ripening or senescence hormone which is also produced by some plant-pathogenic fungi during infection and disease development; (4) Some farmers in Hawaii confuse Cercospora berry blotch with "anthracnose," when in fact the opportunistic and ubiquitous anthracnose fungus (Colletotrichum gloeosporioides) tends not to be the primary agent, but rather a secondary invader of tissues already damaged by Cercospora coffeicola.
Reference links:
(1) Smith, V. E., and Nelson, S. C. (2004) Hawaii Coffee Quarterly, Issue No. 1; (2) American Phytopathological Society list of coffee diseases (J. M. Waller, primary collator, last update 10/29/98); (3) Nelson, S. C. (2005) Coffee Pest and Disease Image Gallery; (4) UH-CTAHR The Farmer's Bookshelf; (5) Liberato, J. R., and Shivas, R. G. (2007). Brown Eye Spot of Coffee (Cercospora coffeicola) Pest and Diseases Image Library; (6) FAO Arabica Coffee Manual; (7) CABI Descriptions of Fungi and Bacteria; (8) CABI Crop Protection Compendium; (8) Nelson, S. C. (2007). An Illustrated Glossary of Tropical Plant Pests (under construction & review).
Reference books and journal articles:
(1) Bittenbender, H.C., and Smith, V. E. (2000). Growing coffee in Hawaii. CTAHR, Univ. of Hawaii, Honolulu, HI.; (2) Daub, M. E. and and Ehrenshaft, M. (2000). The Photoactivated Cercospora Toxin: Contributions to Plant Disease and Fundamental Biology. Annual Review of Phytopathology. Vol. 38:461-490; (3) Staver, C., Guharay, F., Monterroso, D., and Muschler, R. G. (2001) Designing pest-suppressive multistrata perennial crop systems: shade-grown coffee in Central America. Agroforestry Systems 53:151-170.
Additional photographs of interest:
The typical "purple halo" symptom (above) results from premature ripening of diseased tissues. Berry infections typically begin at the blossom end of fruits (where there is a small, circular receptacle which holds water after dew or rainfall), and progresses basipetally along the longitudinal axis of the fruit, toward the peduncle.
Premature ripening of diseased cherries (above), a symptom and a damaging effect of Cercospora berry blotch disease. Prematurely ripened fruits usually are not picked on time and therefore constitute crop loss.
The pruned plant exhibiting nutrient deficiency symptoms (foreground) has Cercospora leaf spots, whereas the normal plant (background) is free of Cercospora leaf spots, illustrating that adequate coffee plant nutrition is a key to preventing this disease (note: the yellowing of the plant in the foreground could be caused by a number of factors).
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