With coffee being a cash crop, diseases affecting coffee plantations are of significant concern. At times, diseases affecting the coffee plantation can wipe out the entire garden. Among two major divisions of coffee, the Robusta is less prone to fungal and pest attacks as compared to the Arabica variety. Various factors play a role in the onset of diseases, including low altitude, warmth, high humidity, water stagnation, dryness, shade, poor soil and wrong plant variety.
Leaf rust disease is caused by a fungus called Hemileia vastatrix, which spreads its light spores through wind, water and animals. The spores remain alive in the soil for a long time and germinate in humid conditions. They cause circular brown spores on the leaf surfaces, ultimately destroying the foliage. Arabica coffee variety is affected by this fungus and Robusta coffee is not affected. Ways to manage this disease include spraying copper fungicides, allowing better air flow and cultivating resistant varieties.
The fungus Omphalia flavida is responsible for this disease, which is prevalent in the Americas. It is more serious than the leaf rust and spreads very fast. Circular yellow spots are formed on the leaf surfaces, growing into gray lesions and causing heavy damage to the foliage. Flower, stem and fruit get affected, causing the fruit to drop. It thrives in cold climates and high altitudes. Leaf spot can be prevented by pruning the shade trees and by spraying Bordeaux mixture.
Coffee Berry Disease
Coffee berry disease was first found in Kenya and is caused by a virulent fungal strain, Colletotrichum coffeanum. This fungus lives in the tree's bark and attacks the berries. The attack takes place very early and affects the green tissues during the berry development. The penetration is deep into the interior causing lesions that turn ash gray. Cold conditions favor the disease and spores spread through rainwater, animals and humans. The disease can be managed by growing resistant varieties, pruning trees, removing affected berries and by spraying copper mixture.
The bacterium Pseudomonas syringae pv. Garcae causes bacterial blight and is mostly confined to Kenya. It is prevalent in cold and wet conditions. It causes lesions on the leaves, which turn brown, dry and roll inwards. The dry leaves do not fall. At times, the whole branches are affected. The bacteria thrive on leaves, berries and bark and cause great damage. Some of the ways to manage the onset of this disease are removing the affected parts and destroying them, spraying copper mixture, increasing shade cover and improving the field hygiene.
Root rot fungus gives rise to yellow-grayish leaves that turn black later and die. The loss created by this fungus is less when compared to the leaf diseases. The fungus growth is very weak and hence the lesser effect on coffee plants. A pit is dug around the affected plant and if the plant dies, it is dug out immediately and the area is left open for a long period.