For more information, see:
UH-CTAHR news release (19 March 2014):
"Citizen science effort encouraged to track new coffee pest"
KITV news (19 March 2014):
"Virus may pose threat to Big Island coffee growers"
Today's date: 8 July 2014
Update: The same symptoms on coffee that are depicted below were found at a coffee farm in the Holualoa area on the Big Island, but the emaravirus was not detected in the symptomatic plants. Therefore, the relationship of the virus to the disease is not firmly established and no causation can be deduced or established. However, the symptomatic plants have been destroyed by the grower.
Today's date: 18 March 2014
New emaravirus infects coffee plants in S. Kona, Hawaii
In January 2014, a coffee farmer in the Captain Cook area of S. Kona, Hawaii sent some coffee (Coffea arabica) leaf samples to Dr. Scot Nelson (plant pathologist with UH-CTAHR) after contacting him via his "Plant Doctor" app. Images of the symptomatic leaves sent to Dr. Nelson appear below:
Chlorotic spots associated with an emaravirus infecting Kona coffee (photographs by Dr. Scot Nelson, UH-CTAHR)
Farm visit. Ms. Andrea Kawabata (Hawaii County Agent, UH-CTAHR) and Dr. Michael Melzer (plant pathologist, UH-CTAHR) visited the farm in February and collected more information and data. Apparently, the affected grower first noticed the symptomatic plants because no cherries were harvested from these plants. Upon closer inspection of the plants, the grower noticed the leaves were covered with circular lesions about 5 mm in diameter (pictured above). The berries had turned to "raisins", but Melzer and Kawabata surmised that the berries were not harvested by the coffee pickers because the berries were small or deformed. The coffee farmer had two locations at the farm having several symptomatic plants, and Melzer and Kawabata could see some symptomatic plants across a fence at the neighboring coffee farm.
Diagnosis. Initially, we suspected infection by Coffee ringspot virus, but we could not find any evidence of that virus by either PCR or by electron microscopy (EM). Under the EM, Dr. Melzer saw some virus-like particles that have a double-membrane structure similar to emaraviruses. He did a PCR test for emaravirus and it was positive. The sequence of the PCR product suggests it is a new virus species. No emaravirus has ever been reported to infect coffee.
Vector. Emaraviruses are transmitted by eriophyid mites which can disperse on wind currents. If this virus is the causal agent, it has the potential to move through a field rather quickly. We doubt the disease will kill any coffee trees, but if it makes the berries unmarketable, the tree essentially becomes an ornamental plant only.
At this stage, we lack sufficient information regarding the following aspects of this disease:
The Hawaii Department of Agriculture has been contacted and expressed interest in survey, risk assessment and eradication of diseased plants. We do not have enough data to say this virus is the cause of the symptoms, but we think it is prudent to conduct some visual surveys and to remove any affected plants as soon as possible before waiting for all the biological data to emerge.
Citizen scientists: Please help us determine the geographic range of the symptoms. If you see the symptoms of the disease at your farm, please contact Dr. Scot Nelson <firstname.lastname@example.org>
UPDATE (18 March 2014): The symptomatic trees at the reporting farm have been destroyed by the farmer. The farmer reports that symptoms were there for at least 6 years and the disease seems to spread very slowly.
REGISTERED MITICIDES FOR COFFEE IN HAWAII: Neem oil may be the most effective miticide registered for application to coffee in Hawaii (http://pesticides.hawaii.edu/hipmrinn/coffee_licensed_products201208.pdf).