Fir Needle Cast, Blight, and Rusts

Needle cast: Lirula abietis-concoloris (Mayr:Dearn.) Darker
Snow blight: Phacidium abietis (Dearn.) Reid & Cain
Fir-fireweed rust: Pucciniastrum epilobii Otth
Fir- blueberry rust: P. geoppertianum (Kueln) Kleb.

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Grand fir and subalpine fir.

Distribution. – Range of hosts in Idaho and Montana.

Damage. – Needles are killed within 1 or 2 years of infection. Severe infections may reduce growth. Christmas trees are often severely degraded by needle diseases.

Identification. – The general pattern of occurrence of needle cast, blight, and rusts is that the greatest infection occurs low in the crown. A single year's complement of needles is usually most severely infected at a time (fig. 111). Chronic infections leave trees with thin crowns and dead lower branches.

Figure 111 - Pattern of needle cast, blight, or rust disease on fir branch.	Figure 112 - Grand Fir needles infected by Lirula Needle Cast have long black fruiting bodies on the underside.

Lirula abietis-concoloris: Fruiting body appears as an elongate black line in the midrib of the lower surface of leaf (fig. 112). Shorter brown or black lines are occasionally found on the upper midrib as well.

Phacidium abietis: Needles are infected under snow (fig. 113). A thin mat of white mycelium grows among snow-covered branches infecting needles. After snow melt, needles turn brown or gray, and white mycelium disappears. Fruiting bodies are brown or black oval or round spots lined up on either side of the rnidrib of the lower surface. After a year or so, the fruiting bodies fall out of gray needles leaving oval or round holes.

Figure 113 - Snow Blight kills needles under snow. Small black dots of fruiting bodies are found on the undersides of dead needles.	Figure 114 - Pustules of sporulating Fir Needle Rusts protrude from the lower surface of needles.

Pucciniastrum spp.: Current year's needles are infected; fruiting bodies develop in early summer (P. epilobii) or late summer (P. geoppertianum). Infected needles turn yellow and have protruding pustules of white or yellow spores on lower surf aces (fig. 114). Alternate host f or P. epilobii are fireweeds, Epilobium spp. Alternate hosts for P. geoppertianum are huckleberry or blueberry, Vaccinium spp.

Similar damages. – Shoot blight by Delphinella balsamea kills current year's needles as well as new shoots. Winter desiccation appears somewhat similar but foliage in the upper crown is usually more damaged than that in the lower crown.

Link to Fir Needle Cast Images in Forestry Images

Link to Fir-Fireweed Rust Images in Forestry Images

References.

Bega, R. V. 1978. Diseases of Pacific Coast conifers. USDA For. Serv. Ag. Hndbk. No. 521, 206 p.

Funk, A. 1985. Foliar fungi of western trees. Canadian Forestry Service, Pacific Forest Research Centre BC-X-265, 159 p.

Ziller, W. G. 1974. The tree rusts of western Canada. Can. For. Serv., Publ. No.1329, Dept. of the Env., Victoria, B.C. 272 p.

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