TO: Members of the Hawai`i Coffee Industry
FROM: Phyllis Shimabukuro-Geiser
Chairperson, Board of Agriculture
SUBJECT: Coffee Leaf Rust Suspected on Maui
Samples of a fungus tentatively identified as coffee leaf rust (CLR) were collected in managed
and wild coffee on Maui. If confirmed, this will be the first detection in Hawai`i. Coffee leaf rust is
one of the most devastating pests of coffee plants. Coffee leaf rust is established in all of the
other major coffee growing areas of the world but has not previously been found in Hawai`i.
On October 21, 2020, leaves from managed coffee in the Haiku area of Maui displaying CLR
symptoms were turned in to the Hawai`i Department of Agriculture (HDOA) on Maui.
Subsequent surveys in the area found plants with symptoms at three additional locations, two of
which were in wild coffee. Molecular analysis will be performed by the University of Hawai`i,
College of Tropical Agriculture and Human Resources (UH-CTAHR) and by the United States
Department of Agriculture National Identification Services to confirm the identity of the causal
It is unknown at this time how the rust got to coffee plants on Maui. HDOA appreciates the
assistance of the multiple agencies that are helping us to determine the extent of this infestation
and how coffee leaf rust may have been introduced to the State.
Coffee leaf rust can cause severe defoliation. Infected leaves drop prematurely, greatly reducing
the plant’s photosynthetic capacity. Vegetative and berry growth are reduced and is correlated
with the intensity of rust in the current year. Long term effects of rust can have a stronger impact
by causing dieback, which effectively 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%...