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Featured Fungus Number 21

Taphrina johansonii
A pathogen on female caktins of trembling aspen

Female catkins of trembling aspen ( Populus tremuloides) each bear dozens of capsules containing seeds. Capsules infected by Taphrina johansonii, an ascomycete, become swollen and are discolored yellow to orange, whereas non-infected capsules remain pale green. On trembling aspen, T. johansonii and the phylogenetically-allied Taphrina populina induce disease on capsules and leaves, respectively.  Several other Taphrina species also cause malformation and discoloring of leaves or catkins of trees in the Salicaceae.  Click on the accompanying photo for detailed information specific to T. johansonii, and for information on Taphrina occidentalis, which causes red, hypertrophied catkins on red alder. [file size: 410 kb]

 

Featured Fungus Number 22

Conidia of Septoria musiva
A pathogen causing leaf spots and stem cankers of hybrid poplars and cottonwoods

Septoria musiva Peck induces leaf spots and stem and branch cankers on susceptible hybrid poplars and cottonwoods (Populus spp.). Stem cankers most commonly occur within 50 cm from ground level, and are slightly flattened, with swollen sides and sunken centers. Conidia, which are pale pink in mass, are produced from pycnidia on cankers and leaf spots.  A closely related species, S. populicola, is the frequent cause of poplar leaf spot epidemics in the Pacific Northwest. Click on the accompanying photo for detailed information on the recent finding of this pathogen in a commercial hybrid poplar nursery in British Columbia. [file size: 523 kb]

 

Featured Fungus Number 23

Umbilicaria hirsuta
A rarely encountered lichen in western North America

The lichen Umbilicaria hirsuta (Sw. ex Westr.) Hoffm. is sporadic and rare throughout western North America. The sole known Oregon population is located in the southwest part of the state on a single noncalcareous rock outcrop in a mixed coniferous/broadleaf forest at an elevation of 946 meters. This distinctive umbilicate lichen can be identified in the field by the presence of submarginal soredia. This is the only sorediate species of Umbilicaria in North America. Other characteristics include a light gray brown upper surface and a rhizinate lower surface. Click on the accompanying photograph of rhizines formed by this fungus to read the recent report from Oregon [file size: 727 kb]. 

 

Featured Fungus Number 24

Leptogium siskiyouensis
A new species from Oregon and California

Species new to science continue to be found, and not all are from tropical rainforests or deep-sea trenches. Leptogium siskiyouensis is a newly described, epiphytic lichen species occurring in southwestern Oregon and northwestern California. The small thalli grow mainly on Quercus species in open mixed conifer-hardwood forests, at elevations of between 610 and 1280 m. Characteristic of this species are the lobes that form a closely adnate, smooth, shiny, grey, circular thallus of up to 3 cm. As each lobe matures the center remains closely attached to the bark but edges raise up almost 90°. Lichens have evolved several kinds of asexual reproductive propagules, one of which is the isidium, a small projection that contains the photosymbiont and strands of fungal hyphae. Isidia detach easily from thalli and are spread by rain, wind, or animal vectors. Once in an appropriate microenvironment, each can develop into a new thallus. Isidia of L. siskiyouensis form a dense fringe along the upturned lobe edges. Visible with low magnification, they typically start as simple, narrow, knobby cylinders, becoming isodiametrically forked and then coralloid to look like upraised hands In addition, they can arise on the lobe surface where they are smaller and less coralloid than marginal isidia. To learn more, click on the accompanying photo to read the article describing this newly-discovered species. [file size: 802 kb].   

 

Featured Fungus Number 25

Leveillula taurica
An emerging plant pathogenic fungus in the Pacific Northwest

Leveillula taurica is a powdery mildew fungus that likely originated somewhere in the Mediterranean region. It has been known in North America since the early 20th century and it can be extremely damaging on crops such as greenhouse-grown tomatoes and bell peppers. Thought to occur on the widest range of hosts of any powdery mildew fungus, it occurs on plants representing more than 50 families. Beginning in the 1990's this fungus has been reported on an increasing number of hosts in the Pacific Northwest where it now appears to be well established. Unlike the case in most powdery mildew fungi which grow superficially on leaves and stems, L. taurica hyphae can penetrate host tissue. For more information about the genus Leveillula, and how to differentiate it from more commonly encountered powdery mildew genera, click on the accompanying photo that shows L. taurica hyphae encircling host cells [file size: 4062 kb]. 

 

Featured Fungus Number 26

Coelomomyces stegomyiae
A potential bio-control agent of mosquitoes

Coelomomyces is a chytrid genus in the Blastocladiomycota (see C. steogomyiae, James et al., Mycologia 98:860-871). Whisler et al., 1975 (PNAS 72:693-696.) showed that in Coelomomyces psorophorae Couch, the diploid zoospore-producing phase developed in the mosquito larvae of Culiseta inorata while the haploid gamete-producing phase developed in the copepod Cyclops vernalis. This discovery established that life cycles in the genus Coelomomyces include an alternation of generations and required two different hosts to complete its life cycle. It is now known that certain insect larvae, for example, those of mosquitoes, black flies, chironomids and tabanids, and a copepod or an ostracod are required to complete the life cycle this obligate host specific fungus parasite. Soon after Keilin's discovery of Coelomomyces stegomyiae in the larva of the mosquito Stegomyia scutellaris (agent of yellow fever) in 1921, the genus became a prime candidate for the control of mosquitoes and other insects because of its host specificity and lethal nature. Today, efforts continue on the use of Coelomomyces as a bio-control agent of insects, including various mosquitoes, the agents of malaria and other diseases. For more information on the research of Howard Whisler, click on the accompanying photo of thick-walled sporangia of C. stegomyiae releasing zoospores [ file size: 835 kb].

 

Featured Fungus Number 27

Bryoria fremontii
A forage lichen occuring in northwestern North America

Forage lichens are pendulous, hairlike species eaten by a wide range of mammals. The main course is Bryoria fremontii, which forms massive dark brown beards on conifers. Abundant in the Pacific Northwest and northern Rocky Mountains where it can achieve a biomass over 1 T/ha dry weight, this species becomes increasingly rare southward and eastward in drier habitats. The palatability of Bryoria fremontii is notable because, unlike most forage lichens, it virtually lacks the secondary chemicals that defend lichens against herbivory. Despite the ecological importance of Bryoria in western North America, studies of its response to disturbance are few. Click the photo to read a paper on how Bryoria responds to the onslaught of disease and disturbance in our forests [file size: 1033 kb].