Forest & Grassland Health

Hemlock-Blueberry Rust

Naohidemyces vaccinii (Wint.) Sato, Katsuy et Hiratsuka

Host(s) in Alaska:

western hemlock (Tsuga heterophyla) and blueberry (Vaccinium spp.)

Habitat(s): western hemlock needles and blueberry leaves


Click on image for larger version.

Hemlock-blueberry rust on blueberry leaves.

Hemlock-blueberry rust on blueberry leaves.

Hemlock-bllueberry rust on western hemlock needles.

Hemlock-blueberry rust on western hemlock needles.

Hemlock-blueberry rust on western hemlock, yellow needle symptoms.

Needle discoloration and needle cast symptoms of hemlock-blueberry rust on western hemlock.

Hemlock blueberry rust on western hemlock.

Hemlock-blueberry rust on western hemlock needles.

Hemlock-blueberry rust on blueberry leaves.

Leaf discoloration symptoms of hemlock-blueberry rust on blueberry.

Current Status & Distribution in Alaska (2020 Update)

Hemlock-blueberry rust is usually a disease of minor importance that can be difficult to find on both blueberry leaves and hemlock needles. However, in 2019 and 2020 this disease was widespread on multiple blueberry species and western hemlock needles in Southeast Alaska. Infected needles were collected this year at several sites near Juneau to allow for molecular verification of the causal fungus. Other fungi, such as Exobasidion maculosum, also cause blueberry leaf spots and were identified from samples in 2019. A few years ago, there was also pronounced needle rust on hemlock, but the causal fungus was not confirmed.

Symptoms, Biology & Impacts

Hemlock-blueberry rust is caused by a heterocyclic rust fungus (Naohidemyces vaccinii) with one lifecycle stage on hemlock needles (rarely on cones) and the other stage on several species of blueberry (Vaccinium spp.). Another needle rust of western and mountain hemlocks, Melampsora epitea f. sp. tsugae, is also present in Alaska, which has lifecycle stages on willow.

Current-year hemlock needles become infected from spores produced in pustules on blueberry leaf. Orange or yellow pustules form on the underside of hemlock needles. Infected needles turn yellow, but hemlocks are not usually heavily infected, thus branches have a scattering of yellow needles among healthy green needles. Infected needles turn yellow and die, but the incidence of the disease on hemlock needles is usually low. Infected needles are shed prematurely. Injury to infected trees is negligible, perhaps slightly reducing growth. The generally low occurrence of this rust is surprising given the great abundance of western hemlock and blueberries in coastal Alaska. Control is not usually warranted, as injury to trees is typically very minor.


Content prepared by Robin Mulvey, Forest Health Protection, Information from the book Insects and Disease of Alaskan Forests has been included.

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