Currently found in nearly all of the world’s coffee growing regions, Hemileia vestatrix is a fungal pathogen causing the disease coffee rust which is devastating central American farms. This disease has been verified on Coffee arabica and Coffee canephora, arabica and robusta coffee; two of the most economically important beans, but may also host on twenty-five other species as well. As is true for many of the rust type fungal diseases, an alternate host was postulated but none has been confirmed as of yet. Coffee rust is the most economically destructive agricultural disease currently occurring, as coffee represents a very important international trade commodity.
Coffee rust presents similar to pear rust or cedar apple rust, when it is actually on the apple or pear trees; beginning as small, pale yellow spots on upper leaf surfaces which get larger and produce orange spores on lower leaf surfaces. This fungus does not form the pustules characteristic of other rusts, coffee rust sporulates through leaf stomata rather than breaking the epidermis. Lesions can develop anywhere on the leaves but tend towards the midrib usually, where moisture is more likely to collect. The earliest symptoms are visible on the lower leaves and the disease progresses up the crown, infected leaves will drop prematurely leaving low limbs bare.
Coffee rust has spread through Central America at an incredible pace, wreaking economic devastation to the area totaling upwards of $1 billion. Nearly 3/4 of El Salvadorian coffee trees are infected, and in Costa Rica coffee rust has claimed about 60% of the population, 70% in Guatemala. Over 100,000 jobs were lost last year due to crop loss, and coffee exports have dropped 15%. Large coffee companies, like Starbucks and Green Mountain, have teamed up with U.S. Agency for International Development to raise funds for training farmers for control and prevention of the disease and to finance repair crops. As of now this joint effort has come up with $23 million, but is it enough? Well, the situation is almost at a tipping point and will become a crisis soon, driving coffee prices up around the world, leaving millions unemployed and abandoning fields to rot, so it may not do the whole job, but it helps.
Another tactic recently being employed, is planting different varieties of coffee, ones that may be more disease resistant than the popular arabica and robusta beans. Some farmers are pruning off infected limbs or removing trees, hoping that will stem the spread. Hopefully some treatment or control method or combination thereof will prove effective soon and slow this environmental and economic disaster.