Chrysomyxa arctostaphyli Dietel
Basidiomycotina, Uredinales, Coleosporiaceae
Hosts: In B.C. the aecial hosts of Chrysomyxa arctostaphyli are white, black, Norway, Engelmann, and Sitka spruce. Elsewhere it is reported on blue and red spruce. The telial host is kinnikinnick.
Distribution: This fungus is widely distributed throughout the range of its hosts in B.C.
Identification: Spruce infected with C. arctostaphyli form conspicuous, perennial brooms (Figs. 28a, 28b, 28c). These may be up to 2 m in diameter and form anywhere in the crown of the tree. During the spring, brooms start out pale green, a result of needle chlorosis, then appear orange in mid-summer when the aecia are formed (Fig. 28d). Needles in the broom are shed in the fall. Telia form on the lower surfaces of kinnikinnick leaves, appearing as crowded groups of localized reddish-brown spots (Fig. 28e, 28f).
Microscopic Characteristics: Spermogonia and aecia on current years needles. Aeciospores 16-25 x 23-35 µm, wall 2-3 µm thick with columnar warts. Uredinia lacking. Telia hypophyllous, reddish-brown. Teliospores 13-18 x 23-64 µm.
Damage: Spruce brooms are often associated with stem deformations, reduced increment growth, broken tops, and tree mortality. Rust brooms also serve as infection courts for decay fungi such as Phellinus pini contributing to increased levels of damage.
Remarks: The brooming symptoms caused by C. artcostaphyli could be confused with mistletoe infections. However, distinguishing features of the rust are the complete loss of needles in the winter and the yellow-orange colour of the broom in the spring and summer.
Baranyay, J. A. and W. G. Ziller. 1972. Broom rusts of conifers in British Columbia. Can. For. Serv., Forest Pest Leaf. No. 48. Victoria, B.C.
Peterson, R. S. 1963. Effects of broom rusts on spruce and fir. USDA For. Serv., Res. Paper INT-7.
Ziller, W. G. 1974. The tree rusts of western Canada. Can. For. Serv., Publ. No. 1329. Victoria, B.C.
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Figure 28a: Spruce broom associated with a dead top caused by Chrysomyxa arctostaphyli. The broom appears dead, with no needles, during the winter months.
Figure 28b: Spruce broom with sporulating aecia on needles.
Figure 28c: Spruce broom with sporulating aecia on needles.
Figure 28d: Sporulating aecia.
Figure 28e: Kinnikinnick, the telial host of C. arctostaphyli. Discoloured spots on the upper surface of the leaves indicate the presence of telia on the lower surface.
Figure 28f: Telia on the lower surface of kinnikinnick leaves.