In 2020 the pest Coffee Leaf Rust (CLR) was discovered first on Maui, then on Hawaii Island, and then on Oahu. This is the second serious coffee pest to have entered Hawaii in the last 10 years. Coffee Berry Borer (CBB) was discovered here in 2010, with significant adverse effects on coffee production levels in Kona and other Hawaii regions.
The newly arrived CLR is caused by a fungus (Hemileia vastatrix) that reduces the coffee plant's ability to derive energy through photosynthesis and causes the plant’s leaves to turn a rust color and often to drop from the tree. Over the last 150 years CLR destroyed coffee production in a number of regions worldwide. An outbreak of CLR in Central America has reduced the region’s coffee production by more than 15%. (Read more about the impacts of CLR on Central America's coffee production in this Atlantic article.)
Hawaii coffee farmers are working with scientists to develop strategies for reducing the effects of CLR. There are different strains of CLR with varying effects on coffee plants. The USDA is working to identify the strain currently present here. In other regions, altitude and climate appear to affect the severity of the damage.
Reductions in the level of CLR damage can be achieved with increased application of fertilizers to coffee orchards and with certain fungicides.
This spring the Hawaii Legislature passed a bill to extend an existing subsidy program to help farmers combat the effects of CBB - and to now include subsidies for combating CLR. The Hawaii Senate also passed a resolution directing the Hawaii Department of Agriculture to identify how CBB and CLR entered Hawaii and take measures to prevent future entry of other invasive species.
Hawaii coffee farmers face a challenging future. 😢