It is well known that during the growth process of any crop there is a great risk of being attacked by all sorts of diseases, fungi and pests.
Coffee, one of the most cultivated fruits in the world, is not spared. Here we explain the fungal disease Phoma costarricensis. It is a fungus that causes the well-known “coffee tree blight” that severely affects coffee plants.
What is a sac fungus?
It is a disease caused by Phoma Costarricensis, usually found in regions of Central and South America and some regions of South Asia, found in coffee plantations at an altitude of 1,200-1,600 masl or higher.
Phoma costaricensis echandi is one of the deadliest fungi for coffee plants because in most cases control and prevention programs for this fungus are very difficult, especially when the plant already has an advanced infection.
The appearance of this fungus coincides with the beginning of the rainy season and the intensity of the infestation increases during the winter, mainly affecting the leaves but also the fruit of the trees and some of the tender stems.
Symptoms appear as irregular brown spots. The leaves affected by this disease shrivel up at the infected or injured site and turn black in color, as if burned.
On tender stems it can also start on tender leaves, i.e. it penetrates through the stem and stops when it reaches the woody tissue.
The portal of entry for the fungus is usually caused by insects that have previously nibbled or eaten at the leaves of the coffee plant, or it can also be caused by the leaves of the plants rubbing against each other when they are shaken by the wind.
This disease leads to the death of plants at the growth sites and premature leaf drop. The shoots of these plants, usually produced by pruning, usually die off due to heavy infestation, resulting in the loss of most seedlings.
Several studies have shown that the fungus develops best at temperatures between 18°C and 22°C; at temperatures between 24°C and 30°C the development is less.
The studies carried out by Cenicafé under controlled laboratory conditions have shown that the presence of water is essential for the germination process of the fungus and its infection process.
In other words, it has been found that periods of high rainfall and/or the presence of precipitation events can favor the spread of the disease.
History and distribution of the ascomycete fungus
As mentioned earlier, this disease is widespread in different coffee tree zones of the world, most of which are closely related to the environmental factors affecting their growth and development.
In coffee trees above 1,600 masl in countries like Costa Rica, Panama, Nicaragua, Colombia and Brazil.
- In Brazil, it was first discovered in Espírito Santo state in 1973, where the symptoms it caused were then confused with boron deficiency.
- In Colombia, the disease was detected from 1951 and affected coffee plantations in the departments of Nariño, Antioquia, Cauca, Cundinamarca, Caldas, Quindío, Risaralda and Valle del Cauca. Of these all, Cauca was the hardest hit.
In these areas, the coffee crops are located at altitudes over 1,600 m, with constant rainfall conditions, low light intensity and temperatures below 20 °C, where the coffee plants are exposed to free sunlight and cold air currents.
It affects all types of coffee, with poorly fertilized coffee trees being the hardest hit by this disease.
Symptoms of coffee sac fungus
As already mentioned, the main symptoms on the plants are dark brown to black necrotic lesions of various sizes in the main growth stages of the coffee plants.
- As the fungus progresses, it consumes the shoots and branches, usually leading to their death.
- Marginal lesions appear on the leaves, extending almost the entire leaf surface and causing leaf deformation.
- Also known as coffee melt. Combustion progresses rapidly in the delicate tissues of the trunks, especially the most delicate, causing downward death.
- The fungus likes to attack young coffee fruits, which leads to colored spots on the stems and leaves.
- Spots are less common on older leaves and when they do appear they are much smaller and a lighter shade of brown.
- According to the Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria (SENASICA), burning coffee has other effects such as nutrient imbalance and a reduction in the productive capacity of coffee trees.
Life cycle of the disease
- Penetration through a wound
- Penetration and infection
- Symptoms appear about 4 to 9 days after penetration
- Proliferation of the fungus
- 48 to 72 days after entry, the fungus spreads
- Stomata or wounds
According to Cenicafe, the fungus enters through stomata and natural openings, with insects involved in a significant percentage of cases.
The cycle of the fungus lasts between 60 and 70 days, depending on environmental and climatic conditions.
Phoma control and prevention
In the article La Muerte Descendente del Cafeto (Phoma spp) by Cenicafé it is mentioned that in areas where the disease occurs it is important to grow seedlings from healthy seedlings and plant them in the shade, with chemical or fungicidal treatment and with windbreaks to cultivate to prevent the spread of the disease.
- In established plots, it is recommended to prune affected branches and shoots, followed by spraying with a fungicide.
- Knowing the climatic conditions and the severity of the disease in the coffee tree area, the application of fungicides should be started before the rainy or winter season, once or twice a month.
- In areas where cold winds lash the crops, planting living barriers or shade for the coffee plants will not only reduce infestations from this disease, but from other pests as well.
- In areas or lots affected by the disease, control measures should not be carried out with fungicides alone, since the effect of the agents used is reduced by the damage that has already occurred.
As a multi-purpose fungicide for a variety of crops to prevent fungal diseases, it can also be used to prevent phoma on coffee trees.
It is usually available as a water-soluble powder.
Extreme caution should be exercised with this fungicide as it should only be used by spraying as it can be very toxic to aquatic fauna and flora, especially crustaceans. This applies to cases like in Costa Rica.
Captan 80 WG
Captan 80 WG is a broad-spectrum, non-systemic contact fungicide that acts immediately by penetrating the fungal spores. It interferes with the chemical processes of the fungus, impairs metabolism and cell division and prevents spore germination.
It acts primarily as a protectant and offers a different mode of action that is ideal for fungicide resistance management.
It easily dissolves in water and should be used to treat phoma in doses of 4 grams per liter of water.
Although technology and agricultural practices have advanced to control diseases and pests affecting crops, most coffee farmers generally do not have the necessary capital to combat them.
On the other hand, it is important to remember that the chemical treatment of coffee affects the quality of the bean.