HONOLULU – Coffee leaf rust (CLR) has been confirmed by the United States Department of Agriculture (USDA) from coffee plant samples collected on Maui last week. Also, in response to the detection on Maui, Hawai`i Department of Agriculture (HDOA) staff began statewide surveys and detected suspect plants at a residence in Hilo on Hawai`i Island on Monday. The suspect plants were tentatively identified as infected with CLR by the USDA Agricultural Research Service in Hilo late Wednesday. Samples are being sent to the USDA National Identification Services in Maryland for confirmation.
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CLR is one of the most devastating pests of coffee plants and is established in all major coffee growing areas of the world, but had not previously been found in Hawai`i prior to its discovery last week on Maui.
“The Hawai`i Department of Agriculture and other partner agencies continue to survey the state to determine the extent of the coffee leaf rust infestation,” said Phyllis Shimabukuro-Geiser, chairperson of the Hawai`i Board of Agriculture. “We are also trying to determine the pathway of how this fungus was introduced into the state.”
CLR can cause severe defoliation of coffee plants. Infected leaves drop prematurely, greatly reducing the plant’s photosynthetic capacity. Vegetative and berry growth are reduced depending on the intensity of rust in the current year. Long-term effects of rust may include dieback, which can have a significant impact on the following year’s yield, with some researchers estimating losses between 30 percent and 80 percent.
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.
Hawai`i has strict importation rules requiring all imported green coffee beans for roasting and associated packing materials be fumigated prior to entering the state to ensure beans are free of pathogens and insect pests. These rules also subject coffee plants and propagative plant parts to strict quarantine requirements if imported to Hawai`i, including a quarantine on all imported coffee plants for a minimum of one year in a state-run quarantine facility.
To report possible coffee leaf rust infestations on any island, call HDOA’s Plant Pest Control Branch at
For more information on coffee leaf rust go to the University of Hawai`i, College of Tropical Agriculture and Human Resources webpages at: