We have all heard of coffee rust, but what is it exactly and why is it such a big deal?
Guatemala, Honduras and Costa Rica have all declared a state of emergency early this year because of this humble fungus. To put the situation into perspective, Guatemala, with a GDP of $US47 billion, has pledged $US40 million to fight coffee rust. That is 9% of their GDP, a massive amount to sink into a project. For a country that relies heavily on agriculture and has lost an estimated two thirds of its 2013/14 crop, this is the kind of response we really need.
Rust is as old as recorded history and is perhaps the most economically important fungal plant pathogen. It has shown up (in various forms) on crops of all kinds throughout history with significant impact to the societies that rely on the host plant for their livelihood. It even shows up in the bible in the form of wheat rust!
So what is it exactly? This little fungus is tougher than your average fungus. Rust (or if we want to get scientific here, Hemileia Vastatrix) is a bit unusual and particularly difficult to get rid of for a couple of reasons. It has a really long life cycle that has lots of breeding stages. One spore will have four to six ‘crops’ over three to five months, producing 300,000 – 400,000 spores!!! It is no wonder it spreads so vigorously. As to why it is hard to get rid of, the fungus actually gets within the leaf tissue itself making it difficult to combat with the application of chemicals alone. To add to this, we do not know the entire life cycle of rust, we do not know if it lives some of its life on an alternate host plant/s but are yet to identify it/them. If we knew the alternative host plant/s we could have a chance of eradicating this problem. Obviously we need more researchers in the field getting answers to this massive problem.
Infection of a plant is complete within 24 to 48 hours of the spores working their way into the leaf flesh. The infection appears as lesions all over the leaf which quickly join together and become narcotic, making the leaf fall off prematurely. Eventually the whole plant will die off as its energy reserves in the roots are used up. As spores are wind borne, crops can become completely infected incredibly quickly.
Sweet Marias (Californian based green bean retailers) recently observed some more vigorous farming methods to combat rust in Guatemala. La Candelaria in the San Juan Alotenango region is working hard to form a best practice against this blight. Every tree on the farm is grafted to robusta root stock which is naturally resistant to root problems such as knot and rot. Each plant also receives six fungicide treatments, and every third row has been reduced to hip high skeletons. In addition to this, all shade trees on the farm have been replaced with smaller plants to reduce the shade. Not all farmers are so proactive against rust, but this is exactly what is required because once it takes hold, it is too late.
Proud Mary’s managed to walk away with some great coffee from Central America this year by buying coffee from high altitudes, which are not as susceptible to rust. It is hard to see the farmers losing such huge crops and having their livelihoods crippled in this way. Lets hope all the effort and funding currently being poured into the rust problem can have a positive effect in the coming years.
