Inland spruce cone rust
Chrysomyxa pirolata is found throughout the province of British Columbia.
Damage, symptoms and biology
This rust periodically damages cones in localized forest areas and can be a serious problem in spruce seed orchards.
Chrysomyxa pirolata attacks only the cones of spruce, not the needles. Infected cones turn brown prematurely and are easily identified by the presence of orange-coloured aeciospores, which form between the cone scales in late summer. A light "dusting" of aeciospores is often observed on vegetation beneath trees with diseased cones. Yellow uredinia are present on the lower leaf surfaces, and sometimes on the petioles of the telial hosts. Chrysomyxa pirolata-infected leaves of Pyrola spp. are slightly chlorotic, more erect, and the upper surface is less shiny than that of healthy leaves.
Seeds are not usually formed in diseased cones, and even when they are produced, malformation and resinosis of the cones hinder seed dispersal or extraction. Those seeds that are formed tend to weigh less and have poor germination.
Microscopic Characteristics: Spermogonia and aecia on cone scales, aecia yellow-orange. Aeciospores broadly ellipsoid, clear, thick walls, warts depressed, forming a reticulate pattern, 17-35 x 22-37 µm. Uredinia hypophyllous, systemic, round, yellowish-red. Urediniospores with yellow contents, ellipsoid, clear walls with warts resembling those of aeciospores, 13-24 x 19-33 µm. Telia hypophyllous, flat, orange-brown.
Canadian Forest Service Publications
Information on host(s)
In British Columbia, the aecial hosts of Chrysomyxa pirolata are limited to spruce species, including Engelmann, white, black, Colorado, and Sitka spruce. Elsewhere in North America it has been reported on red spruce. The telial hosts include single delight and a number of other species of wintergreen where the rust is systemic and perennial.
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