|ARISTIZABAL, LUIS - Synergistic Hawaii Agriculture Council|
Submitted to: USDA-ARS Research Notes
Publication Type: Research Notes
Publication Acceptance Date: 2/18/2021
Publication Date: 2/18/2021
Citation: Aristizabal, L.F., Johnson, M.A. 2021. Survey of coffee leaf rust in Kona, West Hawaii Island. USDA-ARS Research Notes. CBB Notes Number 11.
Interpretive Summary: Coffee leaf Rust (CLR) is the most economically damaging disease of coffee. In coffee-growing countries afflicted by this fungal pathogen, 70-80% of the crop may be lost. CLR was first detected on Maui in October 2020 and in the Kona coffee-growing district of Hawaii Island in November 2020. A preliminary survey for CLR was initiated in December 2020 to determine the incidence and on commercial coffee farms. Overall, 25 coffee lots across 17 commercial coffee farms were surveyed. Farms ranged in elevation from 204–869 m and spanned North to South Kona on West Hawaii Island. Of the 25 lots surveyed, 16 were positive for CLR (64%). CLR incidence ranged from 0–30%, but most fields were observed to be in the early stages of infection (average incidence of infection on CLR positive lots was 5.6%). Early detection of the disease is critical because it allows coffee growers to start a spray program when the infection is still low. Management at this early stage will help to limit widespread spore dispersal and prevent advanced CLR disease, which can result in defoliation and subsequent losses in production.
Technical Abstract: Hemileia vastatrix, the fungus that causes Coffee Leaf Rust (CLR) disease, was reported on Maui in October 2020 and on Hawaii Island in November 2020. A preliminary survey for CLR incidence on commercial coffee farms in the Kona district of Hawaii Island was initiated in December 2020. A total of 25 coffee lots across 17 farms were surveyed. For each lot, 25 trees were randomly selected for sampling. Leaves from two branches in the mid and lower canopy of each tree were inspected for CLR lesions (appearing as yellow spots on the upper leaf surface and orange-yellow spots with spores on the lower leaf surface). Of the 25 lots surveyed, 16 were positive for CLR (64%). Across all coffee lots (25) the average incidence of infection was 3.6% ± 1.2 (Mean ± SEM); when considering only CLR positive lots (16) the average was 5.6% ± 1.8. CLR incidence ranged from 0–30%, but most fields were observed to be in the early stages of infection (< 5%). Evidence of CLR was found on both conventional and organic farms. Shade appeared to be linked to CLR incidence, with 7 out of 11 positive farms having some shade trees. Continued surveys are needed to determine the relationship between incidence/ severity of the disease and microclimate factors such as temperature, humidity and rainfall, as well as how different aspects of farm management impact the disease in Hawaii.