Identification of Armillaria species from Wisconsin and adjacent areas

Abstract

Single-spore isolates from 218 basidiomata of Armillaria from Wisconsin, the upper peninsula of Michigan, and eastern Minnesota were identified to species by pairing with known haploid testers. Collections were made from 25 different host species and were identified as A. ostoyae, A. gallica, A. calvescens, A. mellea, or A. sinapina. The most frequently collected species were A. ostoyae and A. gallica. Within the sampling area, A. ostoyae and A. sinapina were collected only in the northern portions, and A. mellea was collected predominantly in the southern portions. Armillaria gallica and A. calvescens were collected throughout the area. Armillaria sinapina and A. ostoyae basidiomata were found equally on gymnosperms and angiosperms, whereas the other three species were collected predominantly from angiosperms. In addition to the basidiomata collections, 71 cultures of Armillaria were isolated from roots and rhizomorphs in seven 10- to 20-year-old quaking aspen stands in northern Wisconsin. These were subsequently identified by pairing with known haploid testers; A. sinapina and A. ostoyae were recovered most often, whereas A. gallica was isolated less frequently. In comparison with the other species, A. ostoyae was more frequently isolated from lesions on otherwise healthy roots and from roots of recently killed trees. On this basis, A. ostoyae appeared to be more pathogenic on aspen than either A. sinapina or A. gallica.

Key Words:

• Armillaria
• aspen
• basidiomata
• Michigan
• Minnesota
• Wisconsin