Hemileia Vastatrix or more communally known as Coffee Rust, is found in nearly all coffee regions. It is the most common disease of coffee in the world and the most important economically.
World distribution of coffee rust. (Adapted from Schieber, E. and G.A. Zentmyer. 1984. Coffee rust in the Western Hemisphere. Plant Dis. 68:89-93.
The history of Hemileia Vastatrix was first described as "coffee leaf disease" by a English explorer in 1861 in the Lake Victoria region of East Africa. The disease was then reported by Reverend H.J. Berkeley and his assistant, Mr. Broome in 1869 for Gardeners Chronicle.
Urediniospores of Hemileia characteristically are kidney-shaped with spines on the convex surface. (From Berkeley’s original drawing and report in the Gardeners’ Chronicle, 1869).
Coffee Rust occurs on the leaves only. Hemileia Vastatrix in the early season will first appear on the bottom leafs of the coffee tree and slowly progress upward. The infected leafs will drop and leave only an exposed branch and or twig. The first symptoms that can be observed are light yellow spots on the top of the leafs and are small in diameter. The spots will slowly increase in size and mass.
When this happens the start to turn orange and begin to appear on the underside of the leafs. Hemileia Vastatrix sporulates through the stomata rather then the epidermis like other rusts do. Hemileia Vastatrix can start on any part of the leaf but most commonly develops around where dew or rain droplets collect.
The spots center slowly dry and turn from yellow to brown. As the rust lesions continue to to grow they keep produce unrediniospores and expand. The rust on the underside of the leaf can range in color from yellow to red. Hemileia Vastatrix does take nutrients from the leaves of the coffee.
Hemileia Vastatrix lives on mostly the living tissues of its host,Coffee. Do to this the leaves that are infected fall prematurely and reduce the potential of Hemileia Vastatrix to spread into an epidemic. Dry Hemileia Vastatrix can survive on leaves for around six weeks making it able to infect the next Season. When Hemileia Vastatrix does spore ( reproduce) it disperses them through rain and wind on the large scale and on a small scale by insects, birds, and other transient flora and Fona. It takes about 24 to 48 hours if moisture to infect the host plant. Do to this Hemileia Vastatrix only occurs during the rainy season. Hemileia Vastatrix takes about two weeks from infection to spore and will grow for around two to three weeks. A single Hemileia Vastatrix can produce up to six crops of spores in three to five months.
Ways to prevent Hemileia Vastatrix is to fertilize with Nitrogen, and Phosphorus; This can and has show to reduce the plants ability to get Hemileia Vastatrix. Studies have also shown that too much Potassium can increase the plat to Hemileia Vastatrix.
Also proper plant maintenance such as pruning to help from overcropping will reduce the plant to Hemileia Vastatrix.
The use of fungicides that contain copper have shown to be very effective. Copper has a "tonic effect" on coffee plants, that is, it increases yields independent of its effect in rust control. One disadvantage of using copper-containing fungicides is that they must be present on the leaves before infection occurs. Another disadvantage, aside from cost, is that copper accumulates in the soil, particularly in the organic matter, and it can reach levels toxic to plants and to other organisms in the environment. With the use of fungicides you should look to the future management and not the present for control. If you are looking for biological or organic you can look into the "White Halo", it has been showing some evidence it can reduce the viability of Hemileia Vastatrix.
The dithiocarbamate (organic, protective) fungicides are effective for the control of coffee rust and also sometimes have a tonic effect, but their residues do not adhere as well as those of the copper-containing, protective fungicides or the systemic fungicides under the heavy rains of many of the coffee-producing regions.
Hemileia Vastatrix has been an increasing problem do to the ingress of the climate; Mostly the the temperature and rainfall. Do to this Hemileia Vastatrix has been showing up in regions and areas where it was not seen before. Another reason can also be the increases of land use and bad coffee farming practices.
Coffee Rust shot under an Electron Microscope