Coffee rust disease is caused by the fungus Hemileia Vastatrix – an unusual name but is the strongest natural enemy to coffee plants. Since it was recorded, rust has remained a disease of luck, unpredictable, and almost uncontrollable. How diligent farmers can control this disease, let’s find out through the article below!

Learn the signs and ways to prevent rust on coffee trees

About Coffee Rust disease

First, we need to know that Coffee Rust or Coffee Leaf Rust is a fungal strain that causes rust on plants. In microbiology, Rust is considered a group of fungi with high biodiversity and affects many plants. Wikipedia has estimated that there are 168 genera of Rust with about 7,000 species. Each of these is an obligate parasite of only a certain type of host. For example, the fungus Puccinia kuehnii causes rust in sugarcane; P.sorghi causes disease on maize, and H.vastatrix only causes disease in coffee plants.

Hemileia vastatrix (H.vastatrix) alone has 45 distinct species, most of which occur mainly in tropical & subtropical regions of Africa and Asia. H.vastatrix is ​​an obligate parasitic fungus, that is, It survives by getting energy and nutrients from the Specialty coffee plant. All coffee species of the genus Coffea Arabica are genotyped to some extent susceptible to H.vastatrix, with the exception of the Timor and Icatu coffee plants that exhibit high resistance and the cultivar Coffea Canephora (scientific name). of Robusta) is almost unaffected.

H. vastatrix is a fungus that causes rust on coffee plants

Conditions for the occurrence of coffee rust disease

Today, rust can be found everywhere coffee is grown. However, it only thrives in a specific climate and environment:

Firstly, free moisture (rain or heavy dew) is the most important factor affecting the growth of H.vastatrix fungus. Water is essential for the germination and dispersal of fungal spores, so the rainy season is often the peak of disease outbreaks.

Second, the temperature is also a factor in rust development. If it is too cold (below 15°C), the spores will not be able to germinate and likewise, if it is too warm (more than 35°C) the fungus will grow slowly. The optimum temperature for rust growth and proliferation is between 21-25°C (Nutman et al. 1963).

On the other hand, light can also change the way the fungus affects the coffee plant. According to some studies, the underside of leaves was not exposed to direct sunlight (high intensity light) will be more susceptible to rust. And with infected leaves, light can alter the rate of fungal growth.

Effects of coffee rust disease

When the fungus first colonizes the coffee plant, it shows slight discoloration on the underside of the leaves. These blobs quickly turn yellow, followed by a layer of orange “dust” – mature spores. When the rust spots get bigger and occupy most of the leaf area, the photosynthesis and metabolism of the leaves decrease, causing the leaves to fall prematurely. In severe cases, the fungus can appear on young shoots or fruits. However, researchers have found that older leaves are relatively resistant to fungal pathogens and H.vastatrix does not usually cause complete plant death.

The fungus causes complete rust of a coffee leaf

A coffee tree can lose a significant amount of leaves when attacked by H.vastatrix. And when it loses the optimal leaf area, it is not able to carry out the process of photosynthesis, exchange and accumulate nutrients for the fruiting process. As a result, coffee plantations will lose their productivity even years after the rust epidemic has passed.

A leafless coffee branch after being attacked by a rust fungus

Coffee rust disease prevention

Controlling coffee rust is a difficult task, in fact, there is no quick fix to this problem. Outbreaks have occurred and have shown H. vastatrix to multiply rapidly and persist for many years. However, people have applied a few methods below to inhibit the growth of this fungus:

Use copper-based fungicides

Since coffee rust spread throughout the world’s producing regions, fungicides have been used to reduce outbreaks. Chemicals such as propiconazole, tridimenol, tridemfon, and copper oxychloride are only partially effective. Of these, copper-based fungicides are the most common, but have a short duration of action and the effects of resistance of H. vastatrix must be considered.
Because of health and environmental concerns, reducing dependence on fungicides requires increased research into new, more effective and sustainable disease control solutions. One of them can be mentioned as taking advantage of the presence of bacteria and fungi available in the coffee ecosystem to use as a potential biocide against H. vastatrix. Bacterial strains such as Pseudomonas putida, Bacillus megaterium and B.thuringiensis have been isolated, showing promising levels of antagonism against rust. However, this method still needs more time to research.

Disease resistant breeding

Propagation of coffee plants to prevent rust is considered the best disease management strategy, both environmentally and economically. The first effective attempt to select genetic resources for disease resistance was conducted in India in 1911, with the introduction of the Kent variety. However, this resistance was lost after about 10 years of cultivation with pathogen exposure. This gradual loss of resistance was also noticed in C. Liberica and C. Canephora. This led to the discovery that there are more “types” of coffee rust than we thought. Indeed, to date, more than 45 species have been identified (Muller et al. 2009).

CIFC and Hibrido de Timor

By 1950, rust had reached the South American continent, so the governments of the United States and Portugal tried to financially support the establishment of the Coffee Research Center (CIFC). CIFC’s mission in Portugal is to focus research on rust at an international level. Since 1955, CIFC has received and characterized coffee rust, providing breeding programs along with scientific and technical training. One of the first practical results of the CIFC was the demonstration that all cultivars grown at that time in Latin America (including Typica, Caturra, Mundo Novo and Bourbon) were susceptible to rust.

Catimor coffee

With the discovery of the Hibrido de Timor (or Timor Hybrid) population on the island of Timor in 1927, the first rust-resistant genes were introduced in the 1950s. Timor trees have been shown to be natural hybrids between Arabica and Robusta, with resistance to all known rust strains at the time. In 1960, CIFC started a breeding program to transfer resistance from Timor to other Arabica varieties; Caturra and Villa Sarchi were crossed at CIFC to produce populations of Catimor and Sarchimor, respectively. These populations were then developed in Colombia and Brazil and became the main source of later CLR resistant varieties.

Despite the accumulated knowledge about rust disease, however, disease management strategies are still not really effective. This gap can be objectively explained by the large number of environmental changes facing the coffee industry. But, fluctuations in the price of the coffee economy are also responsible for production. When prices do not guarantee livelihoods, farmers are forced to choose between organic farming, with the risk of disease or using fungicides as an economically safe treatment.

Through this article, 43 Factory Coffee Roaster hopes to bring readers a clearer view of the difficulties that farmers, households, as well as the Specialty coffee industry are facing. Every civilized choice in our hobbies and interests contributes to the development of a large supply chain behind. Each cup of fragrant coffee is delivered to the hands of the incessant efforts and struggles of diligent farmers, so please consider carefully so that your choice is wise for the whole community.