Coffee Leaf Rust Tentatively Found on Hilo Coffee Plants

Officials tentatively identify CLR on Hilo coffee plants. (PC: Hawai’i Department of Agriculture)

Coffee plants at a Hilo residence have been tentatively identified as infected with coffee leaf rust (CLR).

The Hawai‘i Department of Agriculture (HDOA) staff conducted statewide survey for CLR after the United States Department of Agriculture (USDA) confirmed coffee samples collected on Maui last week were tainted by the pest.

The samples identified in Hilo are being sent to the USDA National Identification Services in Maryland for confirmation.

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 in to 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 to 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 help to prevent over-cropping and maintain a healthy field.

To report possible coffee leaf rust infestations on any island, call HDOA’s Plant Pest Control Branch at 808-973-9525.

For more information on coffee leaf rust go to the University of Hawai`i, College of Tropical Agriculture and Human Resources webpages at:
https://www.hawaiicoffeeed.com/coffee-leaf-rust—nko.html or http://www.extento.hawaii.edu/kbase/crop/Type/h_vasta.htm