Coffee Leaf Rust or CLR is a devastating disease that affects susceptible coffee plantations. It’s brought by a Pucciniales fungus called Hemileia vastatrix. In order to survive, the rust must come into physical contact with coffee, its obligate host.
It’s called coffee leaf rust because it looks yellow-orange and powdery. It also appears on the leaves’ underside. Young lesions usually appear pale yellow while older lesions are smaller in diameter.
Coffee Rust Life Cycle
The life of the Hemileia fungus starts with the germination of the uredospores. They mainly attack the leaves, but can also be found on fruits and young stems. Then, Appressoria are produced. They produce vesicles to enter the substomatal cavity of the leaves. After a day or two, infection is completed.
When an infection has been successful, the leaf blade colonization and sporulation will happen through the stomata. A lesion can produce 4 to 6 spore crops. After 3 to 5 months, they will release about 300,000 to 400,000 spores. Thus, spread the infection widely.
Coffee Leaf Rust Ecology and History
Coffee Rust destroyed the flourishing Sri Lanka and Java coffee plantations in the 1800s.
This epidemic disease was finally discovered in 1970. During then, it was widespread in Brazil and it was the first known infection in the Western Hemisphere.
In 1989, the coffee rust disease reached Costa Rica and in 1995, it hit Nicaragua.
The 2012 Coffee Rust Epidemic
Researchers were still looking for the solution for this problem when an epidemic hit ten Latin American and Caribbean countries in 2012. The disease became an epidemic and the resulting crop losses pushed coffee prices to an all-time high amid concerns for supply. The reasons for the epidemic remain unclear but an emergency rust summit meeting in Guatemala in April 2013 compiled a long list of shortcomings. These included a lack of resources to control the rust, the dismissal of early warning signs, ineffective fungicide application techniques, lack of training, poor infrastructure and conflicting advice.