Coffee News: from Seed to Cup

A Guide to Common Coffee Pests & Diseases

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Pests and diseases can ruin your coffee crop. An infestation or outbreak that is badly handled can mean financial hardship or even devastation. But do you know which pests and diseases are the greatest threats? And how do you identify them?

Let’s take a look at coffee pests and diseases to better understand what they are and how to handle them.

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Green coffee cherries. Credit: Julio Guevara

What Causes Diseases & Attracts Pests

Like any crop, the coffee plant is vulnerable to pests and diseases. A 2012 report by Fabienne Ribeyre, a researcher at French agricultural research center CIRAD, states that “most coffee diseases are caused by pathogenic fungi and less frequently by bacteria and viruses.”

“Root rot disease, rusts, and coffee berry disease can attack healthy trees without any particular physiological weakness, whereas most of the other diseases of economic importance only occur in trees that are physiologically weakened,” it says.

A coffee farm in El Salvador. Credit: Fernando Pocasangre

But some factors make a coffee crop more vulnerable to infestation or outbreak. Adriana Villanueva is a co-founder of Inconexus, a Colombian coffee exporter. She tells me that the the following factors influence the incidence of pests and diseases.

  • Genetics

Some varieties of coffee are more vulnerable to disease than others. For example, Bourbon Pointu/Laurina is known to be very susceptible to leaf rust.

  • Environmental Conditions

Coffee is produced in many countries and there are pests and diseases in every area. But the specific pests and diseases vary dependent on environmental conditions. For example, the coffee borer beetle thrives in humid conditions.

So when Arabica is grown at lower altitudes, the relative warmth and humidity puts it at increased risk of coffee berry borer. But even if the season is inhospitably dry, the insects can hide in the cherries until the first rains, when they emerge en masse and create devastation.

And some diseases are almost universal. Coffee leaf rust is a fungus that has become one of the biggest threats to coffee around the world. It is present in almost every coffee-producing country, regardless of local environmental conditions.

Coffee seedlings. Credit: Julio Guevara

  • Crop Management

Good agricultural understanding can make all the difference in the control of pests and diseases. Farmers rely on productive and resilient plants to remain competitive. If crops are managed poorly, it could have a serious impact on yield and profit.

For example, damaged coffee plants can be more susceptible to fungal infection and improper fertilization can cause structural weakness. And even something as small as leaving fallen leaves on the ground can be a problem – it increases the likelihood of mold and can provide cover for pests.

  • Economics

Producers who do not make enough money to invest in their farms are more likely to suffer from pests and diseases. This can be self-perpetuating. If a farmer can’t afford fertilizer, new plants, or pesticides, they may be more affected by pests and diseases, and produce a low yield. This in turn means they may not have the resources to invest in next year’s crops and the cycle continues.

A coffee seedling. Credit: Julio Guevara

Which Pests & Diseases Should You Watch For?

Although there are hundreds of pests and many diseases that can affect coffee plants, some are more prevalent than others. Ribeyre’s report says that there are more than 900 species of insects, various other pests (including microscopic parasites, molluscs, birds, and mammals), and a large number of diseases that attack coffee crops.

But it says that “Most pests and diseases are spatially distributed, with many of them restricted to only one continent. Only a small number of pests are widespread throughout the tropics.”

It also explains that the majority of these pests have been accidentally spread through infested coffee shipments. Let’s take a closer look at some of the pests and diseases that affect coffee.

A coffee plant in flower. Credit: Angie Molina

Common Coffee Pests

Insects generally weaken coffee beans and reduce density. The bites from insects also open coffee plants up to secondary infection from fungi and other microorganisms. Infestation by insects not only reduces yield, but can have a considerable effect on coffee profile, with reduction in quality of flavor and aroma.

These are some of the pests you’re likely to encounter on a coffee farm.

  • Coffee Berry Borer

These tiny black beetles are present in almost all coffee-producing countries, where they burrow inside coffee cherries. They are very difficult to manage with insecticides because they are protected by the cherries.

The insects spread worldwide from Africa alongside coffee crops as far back as the 16th century. Café de Colombia states that this pest has caused the most damage to coffee throughout  history.

The coffee cherry with damage from coffee berry borers. Credit: Julio Guevara

In crops affected by coffee borer beetles, yields are reduced because young bored cherries may fall prematurely and all harvested bored cherries are of lower weight.

Coffee berry borer damage also affects the sensory qualities of the coffee and this reduces the commercial value of the crop. If damage is significant, it can cause the cup to taste bitter, tarry, or fermented. Berry borer damage can also cause roasts to be irregular, which has a further impact on flavor.

Find out more in Traps & Training: How to Tackle The Coffee Borer Beetle

A coffee borer beetle. Credit:L. Shyamal via WikipediaCC BY-SA 3.0

  • Coffee Leaf Miner

Coffee leaf miners are two related species of moth – Leucoptera coffeella, which is prevalent in Latin America, and Leucoptera caffeina, which is found in African producing countries.

They affect the leaves of the coffee plant. Café de Colombia explains that coffee leaf miner larvae eat coffee leaves. If several live on the same leaf, it may suffer necrosis of up to 90% of its structure. Necrosis is the death of cells and it appears as dark watery spots or brown papery patches.

Defoliation affects the plant’s ability to photosynthesize. Without photosynthesis, the plant can’t grow properly. Fruit may not mature and the overall yield is likely to be much lower. If immature or dead beans make it into the final brew, they can create bitterness and astringency.

A mealybug on a stem. David Hall via Wikimedia Commons

  • Mealybugs

Mealybugs are a group of insects that feed on a variety of trees and plants. In coffee, they attack various parts, including branches, nodes, leaves, roots, and flower clusters.

They feed on the sap of the coffee plant and secrete a sticky substance that attracts ants. This substance also leads to the formation of a black mold that covers leaves and can reduce photosynthesis.

Reduced sap uptake, circulation, and photosynthesis stresses coffee plants and they tend to produce light or immature beans. This can result in astringency, a metallic taste, or bitterness in the cup.

Coffee mealybugs have been found in Africa, Australia, Asia, and Central and South America.

  • Nematodes

Nematodes are microscopic worm-like parasites. There are several species that attack the root system of coffee plants and feed on their sap. Nematodes can form knots in the roots that prevent the plant from properly absorbing water and nutrients.

Infestation can cause reduced roots, defoliation, and general lack of health in the plants. This can mean low yield and light beans.

Coffee seedlings. Credit: Ana Valencia

Common Coffee Diseases

Disease is also a big threat to coffee production. These are some common conditions.

  • Coffee Leaf Rust

This fungus is a worldwide problem for coffee producers and Colombia has been battling it for generations. The BBC highlights that it has “the power to cripple, or even wipe out, the country’s national product, the base of one of its biggest industries, and one of its most important sources of foreign currency.”

In 2012, coffee rust hit Central America hard. And over the next two years, it caused over $1 billion in damage (USAID).

The disease presents as an orange rust-like dust on the underside of the coffee leaves. It is a cyclical condition that causes defoliation, just like coffee leaf miners. Wind and rain spread coffee leaf rust spores, which thrive at around 70°F/21°C. So the disease is most prevalent in Arabica grown in the warm, humid conditions of low altitudes.

The leaf of a coffee plant affected by leaf rust. Credit: Wikipedia

Because it restricts the growth of new stems, coffee leaf rust has an impact on the next year’s crop as well as significantly reducing yield in the current year.

Plants affected by coffee leaf rust are unable to ripen fully and if they do fruit, will produce light beans that taste astringent. Ribeyre states that “severe attacks of coffee leaf rust may result in dead beans that transform into brown beans after the wet process. These brown beans have a sour flavor and sometimes other off-flavors.”

Find out more in What Are The Main Challenges Faced by Coffee Producers?

A coffee plant affected by leaf rust. Credit: CIAT

  • Coffee Wilt

Coffee wilt is a vascular disease of the coffee tree trunk that is caused by a fungus. It blocks water and sap circulation, causing leaves to fall, branches to die, and cherries to appear ripe prematurely.

Using these red but immature coffee cherries can result in loss of acidity, increased bitterness, and “green” flavors in the cup.

  • Pink Disease

Pink disease is another fungal infection. It appears as webbing and pink encrustation on branches. The infected branches lose their leaves and die. It has been particularly problematic in the coffee-producing regions of Brazil.

A coffee farm in Brazil. Credit: Julio Guevara

How To Prevent Pests & Diseases

The best way to prevent pests and diseases is through good farm management. Variety choice, shade management, selective pesticide use, and plant nutrition are important considerations.

Francisco Quezada Montenegro is an agronomist at Dinamica International Crops, a Guatemalan producer and exporter. He tells me, “Prevention can be aided by good nutrition.”

He says that good nutrition makes a plant more resistant, but that preventative applications of fungicides such as Bordeaux mixture (a copper-based fungicide) are beneficial too. “The importance of copper is that it is the only fungicide that does not create resistance,” he says.

And he emphasizes the importance of monitoring temperatures and humidity “to make the applications at the optimal times and have better coverage.”

Coffee trees with ripe berries at a farm in El Salvador. Credit: Fernando Pocasangre

  • Pruning & Hygiene

Francisco recommends an intensive pruning management schedule that means crops are pruned at least every five years. He says that after this age, they become more vulnerable to coffee rust disease.

Pruning can leave unprotected wounds on the plant, which are then vulnerable to fungal infection, especially in the rainy season. Be careful to minimize damage when weeding and pruning.

Also be mindful of keeping tools and equipment clean to avoid contamination between crops. These measures for the control of plant diseases are known as phytosanitation.

A coffee plant nursery. Credit: Julio Guevara

  • Monitoring

Monitoring is a key part of keeping coffee plants disease- and pest-free. Monitoring pests and diseases at field level helps prevent large outbreaks and minimize chemical control. Specific guidelines for monitoring vary from country to country.

Jhon Espitia is a coffee producer and agronomist based in Colombia. He says that producers should record flowering and the timing and dosage of fertilization. He recommends using soil analysis to identify specific nutritional needs and scheduling specific dates for fertilization and visual monitoring.

He also says that farmers should keep track of shade, rain, and humidity levels. By considering these factors, you can make an environment that encourages pests and diseases or one that helps keep them away.

Learn more in Combating Leaf Rust With Phone Apps in Guatemala

A view of a coffee farm in Brazil. Credit: Julio Guevara

Pesticides & Alternatives

If your crops are affected by pests or disease, your first thought may be of pesticides. But chemical pesticides can create water contamination, destroy the local ecosystem, and cause the death of wildlife.

Ribeyre’s report says that in some cases, “use of pesticides has reduced the populations of natural enemies, leading to an increase in pest populations a few months after treatment.” There is also public awareness of the human health risks of chemical residues. And methods that avoid pesticides are also important to prevent resistance.

But sometimes pesticides are needed. The same report states that “judicious use of pesticides in a well-managed integrated pest management programme will improve coffee quality.” So you don’t necessarily need to avoid them all together – just look into where other methods may work as well or better.

A coffee tree with cherries. Credit: Julio Guevara

One example of disease control without chemicals is the integrated pest management method used to manage coffee bean borers. This technique uses environmental control and predators.

Café de Colombia explains that wasps are bred and then released within the coffee crops. They seek out the beetles within the cherries and eat them. A mildew is also sprinkled on the crops to destroy coffee bean borer infestations. The organization says that this method has “permitted Colombia to sustain low levels of infestation within its coffee crops to comply with its export obligations in terms of productivity and quality.”

Traps are another example of handling pests without pesticides.

Coffee leaves infected by leaf rust. Credit: Nossa Familia Coffee

Coffee producers face many challenges. While there are many factors you can’t control, such as climate change and global economics, pests and diseases can be managed. Understanding pests and diseases is the first step in controlling them.

So start keeping records and make sure that you are using phytosanitary techniques. Some small changes can reduce the incidence of pests and disease without major investment.

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Written by Angie Molina.

Please note: Before implementing the advice in this article, we advise also consulting with a local technical expert, since differences in climate, soil type, varieties, processing methods, and more can affect the best practices for production and processing.

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