A sample of a rust fungus collected at a residence in Hilo has been tentatively identified by the United States Department of Agriculture Agricultural Research Service in Hilo as coffee leaf rust.
Samples will be sent to the USDA National Identification Services to confirm the identity of the causal agent. If confirmed, this will be the first detection on this island. Coffee leaf rust is one of the most devastating pests of coffee plants. It is established in all of the other major coffee growing areas of the world but had not previously been found in Hawaii, prior to its discovery last week on Maui.
“We were the last coffee growing region in the world to get CLR, so while it’s not unexpected, it is still a bitter pill,” said Suzanne Shriner, administrator of the Synergistic Hawaii Ag Council. “This will increase our costs and lower our yields at a time when many of us are not economically stable because of COVID impacts. I have hope that Coffee Berry Borer has taught us resiliency though, and that we will find a way through this.”
On Oct. 21, leaves from managed coffee in the Haiku area of Maui displaying CLR symptoms were turned in to the Hawaii Department of Agriculture on Maui. Subsequent surveys in the area found plants with symptoms at three additional locations, two of which were in wild coffee. HDOA has sent a memo to members of the coffee industry throughout the state to alert them to the situation. Currently, HDOA is continuing its efforts to survey on Maui and is extending those efforts statewide as well.
It is unknown at this time how the rust got to coffee plants on Hawaii Island. The Hawaii Department of Agriculture is partnering with multiple agencies to determine the extent of this infestation and how coffee leaf rust may have been introduced to Hawaii Island.
Coffee leaf rust can cause severe defoliation. Infected leaves drop prematurely, greatly reducing the plant’s photosynthetic capacity and reducing berry growth. Long term effects of rust can have a stronger impact by causing dieback, which reduces the number of productive nodes on branches. This can have a significant impact on the following year’s yield with some researchers estimating losses between 30% and 80%.
The first observable symptoms are yellow-orange rust spots, appearing on the upper surface of leaves. On the underside of the leaves, infectious spores appear resembling a patch of yellow- to dark orange-colored powder. These young lesions steadily increase in size with the center of the lesion turning necrotic and brown, with the infection eventually progressing up the tree. CLR may also infect young stems and berries.
While there are fungicides that may be used to help control the fungus, one of the key factors to any pest management program is good sanitation practices. Regular pruning and training of the coffee tree helps to prevent over-cropping and maintain a healthy field. These practices help to improve air circulation and also to open up the canopy to allow proper fungicide spray coverage. Good weed control is an important factor as it keeps competition for vital nutrients low, thereby reducing the susceptibility to the rust.
Coffee leaf rust, Hemileia vastatrix, was first discovered in Sri Lanka in 1869 and is now found in the major coffee-growing regions of the world, including Southeast Asia, Africa, and Central and South America.
HDOA is asking that individuals on Hawaii Island not transport coffee plants, coffee green waste, coffee cherries/pulp, used coffee processing/harvesting equipment, used coffee bags or green coffee beans interisland, and if possible, within the island until more is known of the extent of the infestation and actual identification of the fungus.
To report possible CLR infestations on any island, call HDOA’s Plant Pest Control Branch at (808) 973-9525.