While much research remains to be done, knowledge about the disease and prevention techniques is growing. The following shares some basic information about coffee leaf rust, its effect on coffee plants and production, and ways to try to combat the disease.
|The yellow spots on this leaf are coffee leaf rust.
While many farmers have taken steps to control the disease, they can never completely eradicate it. Spores spread from farm to farm in a variety of ways - wind, animals, and people - making prevention difficult once a neighboring field has been afflicted. One way to prevent the airborne spread of the fungus is to surround a field with large-foliage plants to block the spores from reaching the coffee trees. Agricultural engineers also encourage farmers to fertilize and care for coffee plants, because healthy trees are better able to fight the disease than those missing vital nutrients. Preventative formulas can be applied to plants during early stages of the attack. If coffee leaf rust is not immediately treated, farmers may choose to fumigate a field with curative sprays, though these sprays are highly toxic when compared to the preventative formulas. Trees that have already been highly damaged by leaf rust can be cut down to the roots, and the new shoots cared for to try to prevent the fungus from returning.
|New leaves grow on a plant that was stumped.
However, even if farmers are able to eradicate or control leaf rust on their fields, the trees will take at least a year to regrow leaves before they put energy into producing fruit. If a farmer decides to plant new trees or cut old trees to the roots, they will have to wait at least two years for the young trees to bear fruit.
Many farmers whose fields have been hit hard by leaf rust this year say they plan to plant new trees of the varietals Lempira and IHCAFE 90 (noventa) because these are still resistant to the disease. However, according to engineers, planting only these varietals comes with its own set of problems. First, there is no guarantee that the disease won’t mutate and begin affecting them as well; secondly, reducing the variety of plants also reduces variety in coffee flavors and could impact the quality of Honduran coffee; third, these varietals are not resistant to all diseases, and can still be subject to infirmities such as ojo de gallo or the insect broca (coffee berry borer). Lastly, planting only one or two varietals encourages the spread of diseases that affect those types.
Why is leaf rust so bad this year versus past years? Some scientists cite climate change as one factor in the increase of the disease, though others minimize its impact (this New York Times blog post gives more information on leaf rust and theories on the causes.) Certain temperature and rainfall conditions can cause the disease to thrive one year, while remaining in the background during other years. Because not much is known yet about the factors that promote growth of the fungus, it is difficult to suggest strategies to eradicate it, though farmers have found various techniques that help control the plague. Engineers and farmers say that healthy coffee plants (that have sufficient nutrients from rich soil) are better able to combat fungus attacks, as are plants that don’t produce as much coffee (plants that produce many cherries don’t have energy left to fight off the fungus).
|Some coffee is still able to ripen on trees with leaf rust.
UMF’s Gilberto Barrientos, who has been attending trainings and learning about the disease, gives suggestions to farmers based on the state of their farm: for affected fields younger than 15 years, the farmer should wait for new leaves to grow on the plants and use prevention techniques to try to keep the leaf rust from returning. This would include fertilizing the plants to help them recuperate. If the number of rust-affected leaves exceeds 5-10 per plant, he recommends beginning preventative measures. For farms that are older than 15 years or that haven’t been managed in a way that cultivates healthy plants, he recommends cutting down the trees and replanting.
|Honduras has two varietals that are not yet
affected by the coffee leaf rust.
|These coffee trees have been damaged by leaf rust,
and they have lost most of their leaves.