Hemileia vastatrix

Coffee rust ( Hemileia vastatrix )

The coffee rust ( Hemileia vastatrix ) is a rust fungus that infects coffee plants and triggers the same disease. It is the most economically important disease of this culture.

Economic Importance

Originally, coffee rust (german coffee leaf rust, Spanish roya del Cafeto, port. ferrugem do café) with limited gene pool in Central and East Africa and since 1868 to the Old World (Africa, Asia and Australia ) before 1903 for the first time was observed in Puerto Rico. 1970 jumped the fungal disease epidemic in Brazilian coffee plantations of Minas Gerais to the intensive crops in Paraná and Santa Catarina on and from there via Colombia to Central America, where it caused huge economic damage. The damage can affect 30% to 80 % of the plants or even lead to complete crop failure.

Biology

Coffee rust belongs to the order of the stand mushrooms. Host plants of coffee rust are Coffea arabica, Coffea liberica and partly gardenias. Coffea canephora is attacked by a few rust races and therefore serves as genetic material for resistance breeding. A characteristic feature of the fungus is the morphology of its spores, where it can be clearly identified.

Haplont of the coffee rust is not yet identified. The orange Uredosporenlager can be found on the underside of leaves. The spores of the fungus are formed in the Stielhyphen the plant and transported via the stroma into the ambient air. Resistance to Hemileia vastatrix may vary with leaves in different stages of development, particularly at risk are the very young and older leaves.

Droughts survived the fungus in the infected plant organs and can sporulate immediately after rain events and spread to other plants. At the beginning of the rainy season can cause major epidemics, as the spores spread by the impact of rain drops rapidly. Even insects can transfer the spores. The optimum temperature by Hemileia vastatrix is 21 to 25 ° C. The spores are 2-15 days viable and can be transported in infested seeds over long distances. Of the total of 40 fungal races, to race II proves to be particularly infectious.

Symptoms

Coffee rust infects Arabica varieties and through the colonization of leaves to leaf fall of the shrubs. Overall, the vegetative growth of the plant is severely weakened and in heavy infestation can die all stocks. On leaves, circular, white to yellowish spots of various sizes, some with a Uredosporenbelag. Infested leaves become necrotic and die after a short time.

Combat

For over a century prevented strict plant quarantine measures that the coffee rust was transferred from the Old World in Central and South American plantations. Any dissemination has been speculated, possibly by trade winds, infected coffee beans or spore growth on host plants such as gardenias. As the barrier of the Atlantic Ocean was bypassed in the 1970s, the fungus can spread rapidly through the air on all Brazilian plantations. When Hemileia vastatrix spread from south to north through the Central American land bridge, it quickly came to devastating epidemics. In some cases there was total loss and the affected plants had to be destroyed completely.

Coffee cultivation with and without shade trees offers advantages. Cultures without shade trees easier to edit with fungicides during an acute attack. Coffee with shade trees reduces formation of dew on the coffee plants and thus a larger spread. The amount of nitrogen fertilization can affect the appearance of coffee rust significantly. The hyperparasite Verticillium hemileiae can be used in the biological disease controlling coffee rust. The effect of this mycoparasites on coffee rust was described in 2002 in the Mexican coffee cultures.

Fungicides

Were used with fungicides triadimefon as an active ingredient or a variety of copper compounds. Ideally, the application should be made three weeks prior to the start of the rainy season. For Kenyan locations are employed from 6.6 to 7.5 kg, a Cu / ha. Other effective fungicide active ingredients are Fentin hydroxide (2.5 kg / ha) or dithianon ( 3.3 kg / ha) lid in an oily suspension. On Brazilian coffee plantations maneb is mainly in use. For small farms the use of biocides usually is not an option due to the high cost.

Resistance breeding

The Coffee Rust Research Center, Oeiras / Portugal since the 1970s, research is being conducted on the breeding for resistance against coffee rust. Coffee rust shows itself by a large number of physiological races which had the large-scale cultivation of coffee in India, Kenya and Brazil inflicted serious economic damage. The cultivar ' Caturra ' was particularly sensitive to coffee rust, so its cultivation in Colombia had to be severely restricted. " Hybridomas de Timor " proved to be a species that was not affected by most rust strains. So far, nine genotypes were identified that were found to be resistant to coffee rust. In Colombia Cenicafé is commissioned in Chinchiná - Manizales, Colombia, with the provision of local fungus-resistant varieties of coffee. Due to the loss of genetic material of many Coffea wild types and constantly adapting fungus breeds resistance breeding is facing new challenges. The Ethiopia 's Institute of Biodiversity Conservation and Research secures the remaining genotypes and the Ethiopian government has called for a ban on the export of coffee plants and beans.