Pests and Diseases
As with any other agricultural crop, the coffee plant can suffer from attacks by pests and diseases. Below are a few examples of each, and how they can affect quality, yield, and cost of coffee beans.
Black Twig Borer (Xylosandrus compactus Eichhoff)
The black twig borer is native to Asia where it is a serious pest of Robusta coffee, but has spread to coffee growing regions throughout the world where it attacks Arabica coffee as well. Females bore into branches, twigs, and suckers, leaving a pin-hole sized entry. The plant is destroyed through tunneling as well as pathogens introduced by the borer. The black twig borer thrives in humid conditions since humidity facilitates the ambrosia fungus upon which the borer feeds in its younger stages. Infestations can be controlled by pruning (specifically removing unwanted suckers) and shade reduction (Wintgens, 2009).
Cicadas (Quesada gigas, Dorisiana drewseni, Carineta fascicuata, Carineta spoliata, Carineta matura)
Cicadas are often called locusts, though they are actually unrelated. Females lay eggs by cutting into the bark of tree branches and depositing eggs. After hatching, the nymphs falls to the ground where they burrow into the ground and feed from the sap of the tap root and other larger roots. This can cause chlorosis in the outermost leaves of the plant, as well as premature falling of leaves, flowers, and fruits. These systems are more predominant in dry periods (Moraes et al., 2004).
Coffee Borer Beetle (Hypothenemus hampei)
The coffee borer beetle is a small black beetle that bores into the lower portion of the coffee fruit and lays eggs in the seed endosperm. The coffee borer beetle thrives in humid conditions and dense crop spacing. The best means to limit infestations are through proper plant pruning and ensuring that all coffee is harvested and no coffee fruit is left in the fields between harvest.
Coffee Leaf Miner (Leucoptera coffeela)
The coffee leaf miner is a silvery white moth whose larvae penetrate the leaves of coffee plants and feed on the tissues between the epidermis, leaving a hollow area that dries out and results in brown spots. The larvae are around 5 mm long. If not controlled, the coffee leaf miner may cause intense defoliation and loss of production. Infestations are usually greater during hotter and drier periods of the year. The coffee leaf miner was first classified by French entomoligist Felix Edouard Guerin-Meneville in 1842. In Portuguese the Coffee Leaf Miner is commonly called bicho mineiro.
Coffee Red Mite (Oligonychus coffeae) and Southern Red Mite (Oligonychus ilicis McGregor)
The coffee red mite and the southern red mite are both spider mites, around 0.5mm in length and colored a reddish-orange with dark spots. Attacks, which are generally isolated, occur on the upper surface of mature coffee leaves. The leaves lose their shine and turn a brown, yellow, or bronze color. In dry and hot periods, the foliar damage can lead to premature defoliation of the plant.
Coffee White Stem Borer (Xylotrechus quadripes Chevrolat)
The larvae of the coffee white stem borer mine into the stem of coffee plants causing fragility in the plant. Younger plants usually die within one season of the infestation while older plants can survive for several seasons, however, with decreased yields and greater susceptibility to disease. The coffee white stem borer is found in Asia, where it is considered one of the most devastating pests to arabica coffee production.
Green Scale (Coccus viridis Green)
Green Scale, also called Coffee Green Scales, is a pale green color with several black spots on its back. Each female lays 50-600 eggs which then hatch within hours (Wintgens, 2009). Like mealybugs, the scale secretes a honeydew that creates a film on the plant leaves. This attracts ants and other insects, and can lead to the growth of a sooty mold that decreases photosynthesis and depreciates the value of the coffee. Control measures are similar to those for mealybugs.
Mealybugs (Planococcus spp.) e.g. Coffee Mealybug (Plannococcus lilacinus Cockerell) and Citrus Mealybug (Planococcus citri Risso</em)
Mealybugs attack arabica and robusta coffee plants, among others. They can attack the plant at any location, including branches, nodes, leaves, roots, and flower clusters. The mealybugs secrete a sticky honeydew that both attracts ants and leads to the formation of a black sooty mold which covers the leaves and may affect photosynthesis. Infestations are sporadic; however, they are more common in plantations with non-uniform or limited shade (Wintgens, 2009). The coffee mealybug has been found in Africa, Australia, Asia, and Central and South America. Mealybugs can be controlled by maintaing shade at 30% for arabica and 20-25% for Rubsta (Wintgens, 2009), controlling ant population, the introduction of parasitic wasps, and the use of proper insecticides.
Nematodes (Meloidogyne incognita, M. javanica, M. caffeicola, M. arenaria, M. hapla, M. exigua)
Nematodes are worm-like organisms that are 0.1-5mm in length. They attack the root system of plants, feeding on the sap. They can form knots in the roots that inhibit the plant from properly feeding. Symptoms of a nematode infestation are galls, splits, scales and decreased mass in the root system, and chlorosis and defoliation in the upper plant. C. canephora is more resistant to nematode infestations, and thus using seedlings engrafted in C. canephora rootstock is a means of limiting outbreaks.
Red Flat Mite (B revipalpus phoenicis Geijskes)
The red flat mite is a tiny mite (275 microns) and is reddish-orange in color. It is generally found in branches and fruits near the center of the plant. It can be found throughout the year, with populations peaking during dry periods (Moraes et al., 2004). It does not directly harm the plant, but rather transmits viruses to the plant, including the coffee ringspot virus (CoRSV), which in turn causes premature fruit and leaf drop.
Soldier Fly (Stratiomyiid Fly) (Chiromyza vittata Wiedemann)
The Stratiomyiid Fly is found in the Sul de Minas (Southern Minas) coffee region, especially in colder parts of the region (Moraes et al., 2004). The larvae attack the root system during the coffee plant’s initial development, thereby reducing production. These attacks also allow the entry of pathogenic fungi such as Fusarium (Waller et al., 2007). The Stratiomyiid Fly is aptly called the mosca-de-raiz, or root fly, in Portuguese.
Bacterial Blight (Pseudomonas syringae pv garcae)
Bacterial Blight, also called Elgon Die-back, was first identified in Garca, Sao Paulo, Brazil, thus its name “garcae.” It normally occurs in seedling nurseries and affects plant leaves and tissue. Leaves initially appear to be water-soaked, followed by the appearance of necrotic brown lesions surrounded by yellow rings. The leaves eventually dry, curl up, blacken and die; however, they do not fall from the tree (Wintgens, 2009).
Brown Eyespot & Berry Blotch (Cercospora coffeicola)
The cercospora coffeicola fungus may attack both the leaves and the coffee berry. The infected leaves show tan spots with grayish-white centers. On green berries, the lesions are sunken and are brown in color with an ashy center. They are sometimes encircled by a purple “halo,” or tissue that has ripened prematurely due to the infection. In red coffee fruit, the lesions are larger, black in color, and can sometimes penetrate all the way to the seed, causing the pulp to adhere to the parchment (Nelson, 2008). Cercospora causes defoliation as well as damage to the coffee fruit.
Phoma (Phoma costaricensis Echandi)
Phoma is a soil fungus that can attack the coffee leaves and fruit. Coffee leaves attacked by the fungus will develop black or brown spots; coffee fruit will develop black spots while still green/unripe. Climates that are cold, humid, and windy favor phoma attacks, which generally occur after blooming and before fruit ripening. Effects can be mitigated through the use of wind-breaks in areas susceptible to phoma.
Coffee Berry Disease – CBD (Colletotrichum kahawae Waller and Bridge)
Coffee berry disease (CBD) is caused by the fungus Colletotrichum kahawae. CBD was first documented in 1922 in Kenya. It attacks coffee berries at any point in their maturation; however, only symptoms detected on young berries can be clearly diagnosed (Wintgens, 2009). The disease can appear in “active” form and “scab” form. In the “active” form, dark-colored indented spots appear on the coffee bean and are followed by a pale pink crust as the spores develop. The berry is destroyed in a matter of days and reduced to an empty, blackened and dried out pouch. The “scab” form is a much milder attack where several small concave spots form on the berry.
Coffee Rust (Hemileia vastatrix)
Coffee rust is fungus that attacks coffee plants. Its color can range from yellow to orange. First documented in Kenya in 1861, it is now known to be in nearly every coffee-producing region in the world. Spores set in on the underside of leaves and can cause severe defoliation, impaired photosynthesis, and a decrease in crop production. Copper-based chemicals have been somewhat effective in combating coffee rust, as have fungicides such as Triadimefon, Cyproconazole and Hexaconazole. Due to the historical significance of its destruction, much research has been conducted in genetic resistance to coffee leaf rust resulting in the development of such varieties as Catimor, Colombia, Ruiru 11, and Icatu.
Borem, F. ed. Pos-colheita do cafe. Lavras: Editora UFLA, 2008.
Moraes, J et al. Estrategias e Taticas de Manejo Integrado de Pragas do Cafeeiro. Lavras: Editora UFLA, 2004.
Nelson, S.C. Cercospora Leaf Spot and Berry Blotch of Coffee. Plant Disease. PD-41, 2008.
Waller, J et al. Coffee Pests, Diseases, and Their Management. Oxfordshire: CABI, 2007.
Wintgens, J. N. Coffee: Growing, Processing, Sunstainable Production (2nd ed.). Weinhem: Wiley-VCH, 2009.