Inland spruce cone rust

Inland spruce cone rust - <em>Chrysomyxa pirolata</em>, the causal agent of spruce cone rust, fruiting on pyrola, the alternate host of this rust fungus.
  • Latin name: Chrysomyxa pirolata G. Wint. in Rabenh.
  • French name: Rouille des cônes de l’épinette (régions intérieures)
  • Division: Basidiomycota
  • Class: Uredinales
  • Synonym(s): Chrysomyxa pyrolae (DC.) Rostr. 1881
Description

Micro-habitat(s)

Cone

Distribution

North America

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.

Other information

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

Inland spruce cone rust

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.

Main host(s)

Black spruce, Colorado spruce, Engelmann spruce, red spruce, Sitka spruce, white spruce

Photos
  • Inland spruce cone rust Chrysomyxa pirolata, the causal agent of spruce cone rust, fruiting on pyrola, the alternate host of this rust fungus.
  • Inland spruce cone rust Chrysomyxa pirolata, the cause of spruce cone rust, fruiting on white spruce cones.
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