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Source: Bar Talks [edited]

Coffee leaf rust (CLR) is confirmed to have spread across Hawaii's islands.
According to The Hawaii Department of Agriculture (HDOA), the disease has been found in Holualoa [island], shortly after [it] was discovered [on] Maui [ProMED-mail post 20201029.7901867]. CLR is found in all major coffee-growing areas of the world but had not previously been found in Hawaii.
As surveys continue across the state, HDOA is preparing interim rules that will hopefully prevent the spread of the fungus. They include restricting the movement of coffee plants and coffee plant material from islands found to have CLR to [islands where it] has not been detected.
HDOA's field guide can be found at:
[Byline: Monica Chan]
Communicated by:
[Coffee leaf rust (CLR; also called orange rust) is caused by the fungus _Hemileia vastatrix_, one of the most feared pathogens of the crop. Of the 2 coffee species grown commercially, _Coffea arabica_ (arabica or highland coffee) and _C. canephora_ (robusta or lowland coffee), CLR affects only arabica varieties, which are usually preferred for their taste. The rust has completely destroyed coffee industries in several countries. The disease is characterised by yellow-orange powdery lesions on the underside of leaves, where it attacks through stomata, but it rarely occurs on stems or fruit. CLR can lead to complete defoliation with death of the host plant.

Fungal spores are spread by wind, rain, and mechanical means. Disease management relies mainly on multiple fungicide applications during the rainy season. Rust-resistant cultivars exist, but the crop is generally of poorer quality. More than 30 races of the fungus have been detected, making it particularly difficult to establish durable host resistance.

New fungal strains adapted to higher-altitude conditions, which may also show additional fungicide resistances, have emerged in Central America, making CLR control in the region considerably more difficult (for example, see ProMED-mail posts 20170515.5038218 and 20120920.1301244). Generally, fungal spores that are wind-borne or can easily be carried on travellers' clothes, such as for CLR, pose a very high biosecurity risk. For Hawaii, no suggestions seem to have been made so far as to a possible origin of the incursion.


CLR symptoms:, and

Additional news stories: and
Coffee leaf rust information and background: (review),,, and
CLR resources:
_H. vastatrix_ taxonomy:
Arabica coffee varieties:
- Mod.DHA
HealthMap/ProMED map:
Hawaii, United States:]


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