Hemlock (Tsuga spp.)-Rusts


Cause Two different rust have been reported in the PNW including Hemlock needle rust, Naohidemyces vaccinii (formerly Pucciniastrum vaccinia), and willow rust, Melampsora epitea f. sp. tsugae. The OSU Plant Clinic has never received samples of hemlock rust but N. vaccinii has been reported from all states, however, T. minima has not been reported on hemlock in the PNW. Injury due to hemlock needle rust is negligible with just thinning foliage and perhaps slightly reducing growth.

Symptoms Hemlock needle rust produces circular, yellow-orange pustules on the underside of current-year needles. The pustules have a dome-shaped covering with a centrally located hole. Infected needles turn yellow, but are usually scattered amongst green, uninfected needles. Yellow needles are shed prematurely. Willow rust is very similar, however, it lacks the dome shaped covering.

Cultural control - If needed, remove blueberry, huckleberry and/or willow from the production area.

Chemical control Not generally needed.

Reference Sato, S., Katsuya, K., and Hiratsuka, Y. 1993. Morphology, taxonomy and nomenclature of Tsuga-Ericaceae rusts. Transactions of the Mycological Society of Japan, 34:47-62.