Coffee Rust

Coffee Rust

Why do the British drink so much tea? The answer, in part, to that question can be traced to the coffee rust epidemic of the 1870's and 1880's. During that time, coffee production in Asia and Africa was virtually wiped out. Many of the countries affected were British colonies at the time. The epidemic began in Ceylon (now known as Sri Lanka) in 1867 and quickly spread to other countries. Many factors led up to the epidemic, one of the most important was the destruction of native jungles in Ceylon and the establishment of an agricultural monoculture of coffee. The destruction of the agricultural base also led to economic problems and some affected countries switched to tea production as a source of income. The fungus Hemileia vastatrix Berk causes coffee rust. & Br. The rust is most severe on Coffee arabica but all coffee species are susceptible. Coffee rust was restricted to the Eastern Hemisphere until 1970 when it first appeared in Brazil. Since that time it has spread to other coffee producing areas in South and Central America as well as Mexico. The causal organism is a very unusual rust fungus. Its life cycle and urediospore shape are very much different than the other rust fungi. Hemileia vastatrix survives in the tropics as urediospores, uredia and mycelia. Teliospores and basidiospores are produced but no alternate host has ever been discovered so their role in the life cycle is inconsequential. Hemileia vastatrix exists in several races. The races arise as a result of mutation rather than genetic recombination since basidiospores are essentially nonfunctional. While most urediospores are round or oval, those of Hemileia vastatrix have been described as looking like hedgehogs. They are spiny (echinulate) on their upper curved surface and smooth (glabrous) on their flat lower surface. Wind, rain and possibly insects disseminate these spores. The fungus may also be spread via infected plant material. The spores germinate under conditions of high humidity and enter the host through stomata on the lower leaf surface when free moisture is present. The fungus becomes established as mycelium within the host and then forms a uredium on the lower leaf surface. The uredium may also develop into a telium. The pathogen does not have a distinctive over-seasoning cycle since its host is an evergreen and its tropical environment remains fairly constant. However, disease progression may be arrested during the dry period between monsoons.

Symptoms

The initial symptom of the disease is a small spot on the lower leaf surface. Spots are pale yellow to orange depending on the race of the fungus and appear powdery as a result of spore production. Leaf spots are circular and may coalesce to form large areas of diseased tissue. At this point defoliation occurs. Younger leaves are generally more susceptible than older leaves. Plant may releaf and repeat the infection cycle. The consequence of repeated infections is reduced vigor and yield. Tip die back and eventually death of the tree are the final outcomes of a severe rust infection.

Plant Health Management

Fungicide Application.

Harry Marshall Ward, the man who did the most extensive work on the disease introduced the idea of preventative fungicide application. He suggested that fungicide application be correctly timed to control the organism at the most vulnerable point in its life cycle. In the case of coffee rust, Ward determined that the fungicide needed to be on the leaves just prior to spore germination. Initially, sulfur containing compounds were used. Today, Bordeaux and other copper containing fungicides are still used to control coffee rust. In addition, the development of systemic fungicides has also helped control this disease. Chemicals such as triadimefon (Bayleton) and pyracarbolid (Sicarol) are alternated with protectant fungicides to provide a curative treatment.

Allow Good Air Movement Through the Planting.

This management strategy has been achieved by decreasing plant density at planting and incorporating new pruning techniques that allow for better airflow.

Resistant Plant Material.

Rust resistant coffees have been identified and researchers have been working to incorporate their resistance genes in breeding programs.

References

Agrios, G.N. 1978. Plant pathology, 2nd ed. Academic Press, Inc. New York, NY. 703 pp.

Large, E.C. 1962. The advance of the fungi. Dover Publications, Inc. New York, NY. 488 pp.

Schieber, E. and G.A. Zentmyer. 1984. Coffee rust in the Western Hemisphere. Plant Disease 68:89-93.

Wellman,F.L.1953. Some important diseases of coffee. Pages 891-896 In Plant diseases the yearbook of agriculture 1953.USDA House Document No. 122. Washington, D.C.

Useful Links

Texas A&M University

Highlighted Area

E.C. Large gives a very interesting account of the coffee rust epidemic in Ceylon. It is especially interesting to note the problems that arose when tropical land was destroyed and restructured for an agricultural monoculture since this practice is still going on in parts of the world today. It is also interesting to follow the progress of Harry Marshall Ward, a young British botanist sent to Ceylon to study the organism. Coffee growers were expecting him to come up with a quick and absolute cure for the disease. Their were not meant but we acquired a whole new way of looking and plant health management through preventative fungicide application.

Caveat

This description is presented for information only and no endorsement is intended for products listed, nor criticism meant for products not mentioned. Always consult the product label before purchasing and using any pesticide.

Material contained on the Links from the page are the responsibility of the linked page's author(s).

This page was drafted by: Jane Christensen, Department of Plant Pathology, University of Nebraska-Lincoln

Disease images were provided by: Dr. David Wysong, Department of Plant Pathology, University of Nebraska-Lincoln

Questions, Comments, Complaints and Complements?

This page is authored and maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln

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