Rust Cankers Research Articles

Whitebark pine foliar fungal endophyte communities in the southern Cascade Range, USA: Host mycobiomes and white pine blister rust

Abstract We present an assessment of relationships between correlates, signs, and symptoms of white pine blister rust and fungal endophyte communities of whitebark pine (Pinus albicaulis) foliage in the southern Cascade Range, OR, USA. Parsimonious combinations of historically important predictors of blister rust provided effective logistic models (AUC = 0.83) for predicting blister rust infection in whitebark pines at our sites. Holding ten other predictors constant, multivariate endophyte community structure varied significantly with host tree diameter, mountain aspect, the latitudinal coordinates at which samples were collected, and proximal alternative host plants of the white pine blister rust pathogen. After controlling for multiple comparisons, mountain aspect remained a significant source of variation in endophyte community composition even at the taxonomic rank of class, while the presence/absence of blister rust cankers did not remain significant. We discuss overarching mechanisms that may contribute to novel trends observed in mycobiome variation.

Topographic influences on the distribution of white pine blister rust in Pinus albicaulis treeline communities

The exotic disease white pine blister rust (caused by Cronartium ribicola) damages and kills whitebark pine (Pinus albicaulis), even in the extreme environments of alpine treeline communities. We surveyed P. albicaulis trees and tree islands for blister rust in 2 distinct alpine treeline communities in Montana, USA, and examined meso- and microtopographic factors potentially related to the climatic requirements for blister rust infection. For each of 60 sampling plots, we created high-resolution digital elevation models, derived microtopography variables, and compared these and distance to water feature variables with blister rust occurrence and intensity (number of cankers per infected tree) for every sampled P. albicaulis tree. Infection rates were 19% (of 328 sampled trees) and 24% (of 585 sampled trees) at the 2 sites. Tree island P. albicaulis had higher infection percentages than solitary trees. Using Bayesian analysis and a zero-inflated Poisson regression model, we determined that solar radiation and moisture-related variables correlated with both presence and number of blister rust cankers on P. albicaulis. Site factors that influence moisture, such as local topography, hydrology, and climate, differed between the 2 treeline study areas, which may account for the model variability.

First Report of the White Pine Blister Rust Pathogen, Cronartium ribicola, in Arizona.

White pine blister rust, caused by Cronartium ribicola J.C. Fisch., was found on southwestern white pine (Pinus flexilis James var. reflexa Engelm., synonym P. strobiformis Engelm.) near Hawley Lake, Arizona (Apache County, White Mountains, 34.024°N, 109.776°W, elevation 2,357 m) in April 2009. Although white pines in the Southwest (Arizona and New Mexico) have been repeatedly surveyed for blister rust since its discovery in the Sacramento Mountains of southern New Mexico in 1990 (1,2), this was the first confirmation of C. ribicola in Arizona. Numerous blister rust cankers were sporulating on 15- to 30-year-old white pines growing in a mixed conifer stand adjacent to a meadow with orange gooseberry bushes (Ribes pinetorum Greene), a common telial host in New Mexico. Most of the observed cankers were producing their first aecia on 5-year-old branch interwhorl segments (i.e., formed in 2004). The two oldest cankers apparently originated on stemwood formed about 14 and 21 years before (1995 and 1988). Neither uredinia nor telia were seen on expanding gooseberry leaves in late April, but these rust structures were found later in the season. Voucher specimens deposited in the Forest Pathology Herbarium-Fort Collins (FPF) were determined by host taxa and macro- and microscopic morphology as C. ribicola-white pine with typical cankers, aecia, and aeciospores (1). Six collections of aeciospores from single, unopened aecia provided rDNA sequences (ITS1-5.8S-ITS2, primers ITS1F and ITS4) with two different repeat types (GenBank Accession Nos. HM156043 and HM156044 [J. W. Hanna conducted analysis with methods described in 3]). A BLASTn search with these sequences showed 100 and 99% similarities, respectively, with sequences of C. ribicola, including accessions L76496, L76498, and L76499 from California (4). Additional reconnaissance of white pines on the Fort Apache Indian Reservation and neighboring Apache-Sitgreaves National Forests was conducted from May through September 2009. Although the blister rust infestation was distributed over more than 100 km2 of forest type, infected trees were restricted to mesic and wet canyon bottoms (climatically high-hazard sites) and were not found on dry sites-even where aecial and telial hosts occurred together. Recent dispersal within the White Mountains was suggested by a presence of infected gooseberry plants on several sites where infected white pines were not yet evident. Geils et al. (1) concluded that the initial infestation in New Mexico had originated by long-distance, aerial transport from California to the Sacramento Mountains in 1969. Since then, numerous additional infestations in the Southwest have been discovered; but we do not know which of these (including Arizona) resulted by dispersal from California or New Mexico. Although rust may eventually infest many host populations in the Southwest and disease may kill most trees in some locations, differences in site hazard and spread provide managers with numerous opportunities to maintain white pines and Ribes spp.

Blister rusts in China: hosts, pathogens, and management

SummaryChina has 12 taxa of white pines (subgenus Strobus), including species of wide distribution valuable to plantation forestry and species of rare endemics only distantly related to other white pines. The most important forest diseases of these white pines are caused by the blister rust fungi of the genus Cronartium that alternate to telial host species of Ribes and Pedicularis. The most serious infestations have occurred in southwestern China on Pinus armandii and in northeastern China on P. koraiensis. The blister rust pathogen on P. armandii has usually been identified as Cronartium ribicola. Several lines of evidence, however, imply this pathogen on P. armandii is different from a pathogen on P. koraiensis that appears more closely related to C. ribicola in North America, Europe, and other Asian countries. In China, C. ribicola is designated as a quarantine pest. Silvicultural control of blister rust relies on pruning and thinning infected trees, herbicide removal of telial hosts, and chemical treatment of blister rust cankers. Although plantation forestry is important in China, little information is available on the genetics of resistance in Chinese white pines to native blister rust fungi. Challenges and opportunities are identified in forest management and research for disease assessment and control, rust systematics and biology, and genetic interactions in the white pine blister rust pathosystem.

Molecular and Morphological Evidence for Interspecific Hybridization Between Cronartium ribicola and C. comandrae on Pinus flexilis in Southwestern Alberta

In May 2003, a survey was conducted in southwestern Alberta, east of the Rocky Mountains, to determine the extent of the spread and genetic diversity of white pine blister rust, which is caused by Cronartium ribicola J.C. Fisch. Aeciospores were sampled from white pine blister rust cankers in three infected limber pine (Pinus flexilis James) stands separated from one another by 100 to 215 km. DNA genotypes were determined for 12 codominant PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism) loci representing genes derived from an EST library. At each site sampled, some aecia displayed DNA genotypes that were heterozygous at all loci and possessed novel alleles (GenBank Accession Nos. DQ009533-DQ009611). At Waterton Lakes, Kananaskis County, and Porcupine Hills, 29%, 11%, and 3% of sampled aecia and 38%, 33%, and 10% of sampled trees, respectively, possessed these unusual profiles. In May 2004, similar genetic profiles were found at two of these sites, Waterton Lakes and Kananaskis County, at 17 and 25% of sampled aecia (25% of sampled trees). In each of these aecia, genotyping and sequence analysis revealed this pattern was due to the presence of one C. ribicola and one C. comandrae Peck. allele at each of the 12 loci. Scanning electron microscopy (SEM) revealed aeciospore morphology that was intermediate between C. ribicola and C. comandrae. Aeciospores were longer (16 to 20 × 25 to 40 μm) than the expected range for C. ribicola (18 to 20 × 22 to 31 μm) (3). They were also fusiform, obovoid or short-to-long ellipsoid, but not pyriform-acuminate as in C. comandrae, and without a true conspicuous smooth spot as in C. ribicola. This provides evidence for interspecific hybridization between C. ribicola and C. comandrae, the causal agent of comandra blister rust. We hypothesize that the presence of nearby C. comandrae-infected lodgepole pine (P. contorta Dougl.) could have led to spermatization of C. ribicola receptive hyphae by C. comandrae pycniospores, resulting in the formation of hybrid aecia. An important question is whether these hybrids have a different host range that could potentially extend its geographic range in areas where the telial host, Ribes spp. L., is not abundant. The hybrid rust Melampsora × columbiana Newcombe was shown to exhibit virulence against certain hybrid poplar clones that had previously been reported as resistant against both parental rusts (M. medusae Thuem. and M. occidentalis Jacks) and abundant pathogenic variation has been observed (2). Furthermore, the ability to colonize unexpected hosts could provide fitness advantages over parental species, as was observed in Phytophthora spp. pathogenic on alder (1). Host range and virulence assays should be conducted to assess the potential impact of this hybrid.

Effect of plant age and length of growing season on the development of blister rust cankers in western white pine

The hypothesis that resistance to blister rust in western white pine increases with tree age and a short growing season was tested. For a short growing season, 18 clones (40 ramets) from mature parent trees were inoculated and placed at a high-elevation site (1000 m). Resistant and susceptible seedlings (68 and 214, respectively) were also inoculated and established at the high-elevation site. After 3 years, there were cankers on the resistant (97%) and susceptible (99%) seedlings, while none of the 40 older ramets were infected. For a longer growing season, the surviving 38 ramets (17 clones) were reinoculated and maintained at a low-elevation site (50 m) and observed for canker development. After 3 years, 11 ramets (10 clones) became infected. Eight of the cankered ramets (73%) had slow-canker-growth resistance responses. These observations are consistent with the above hypothesis. There are implications for the deployment of certain resistant stocks, as the effectiveness of resistance to disease may vary with elevation and latitude as these factors influence the length of the growing season

Environmental and inoculum-source effects on resistance of Idaho F2 western white pine in British Columbia

An Idaho orchard seed source (RTB F2) of western white pine (Pinus monticola) was confirmed as having fewer blister rust cankers (average 18%) caused by Cronartium ribicola than native stock (average 62%) in plantations in the interior of British Columbia, Canada, but not at low, coastal elevations (average 59%). Placing RTB F2 seedlings at different sites after five separate inoculation tests confirmed that more cankers developed at the coast than in the interior of British Columbia. This suggested that differences between coast and interior results were due to environmental effects, not to inoculum sources, as coastal and interior inoculum caused the same effects. Putative resistance traits in RTB F2 are needle shed and fungicidal short shoot. However, needle shed occurred only at one site, and it was associated with poor growing conditions, not genetic traits. Most seedlings classified as fungicidal short shoot 2 years after inoculation eventually developed cankers. However, after 3 or 4 years, some seedlings shed their infected needles naturally without developing cankers (a spots-only response), and others developed resistant cankers called slow canker growth. Based on published data, only 35% of the inoculated seedlings were expected to be cankered, but because needle shed did not occur, and because fungicidal-short-shoot seedlings were observed longer than in the previous study, 98% (mean value) were cankered when planted at the coast, and 74% (mean value) were cankered when planted in the interior. As an alternative to a needle-shed trait to account for the good field resistance (few cankers) of Idaho F2 stock in the British Columbia interior, it is hypothesized that good field resistance is the result of both a short growing season and natural infection at a later age, which enhances resistance responses

Effect of plantation design on stem‐infecting form of rust in willow biomass coppice

Planting of genotype mixtures is a major strategy for the non‐chemical control of willow rust in short‐rotation coppice willows grown for biomass. In 1997 and 1998, the relative severity and spatiotemporal distribution of stem canker damage by Melampsora spp. on Salix viminalis `Bowles Hybrid' in a field trial containing monocultures and two design mixtures (random or regular) of three or five genotypes were assessed. Sphaerellopsis filum, a hyperparasite of Melampsora spp. was detected in all plots during the summer (1998) between the time of the two canker assessments. The percentage of rust pustules with this hyperparasite was initially greater in monoculture plantings than in mixtures in June, but by July, more than 92% of pustules were parasitized, irrespective of plantation design. The stem rust assessments showed that, in general, there were fewer cankers per stool in plots containing mixtures of willow genotypes compared with monoculture plantings. The distribution of rust cankers was different between monocultures and willow mixture designs, with differences between years for monocultures.

Establishment of White Pine Blister Rust in New Mexico

White pine blister rust (WPBR) (Cronartium ribicola Fischer) is a recently established pathogen of southwestern white pine (Pinus strobiformis Engelm.) and Ribes L. (currants and gooseberries) in New Mexico (Hawksworth, 1990). Based on the apparent age of the oldest canker found, the outbreak began about 1970 on the western escarpment of the Sacramento Mountains, Otero County (Geils et al., 1999). By 1999, the rust was found in several additional areas in New Mexico and on 62% (111 of 180) of plots distributed across the range of white pine in the Sacramento Mountains (Geils et al., 1999). Several hypotheses propose to explain the spread of WPBR from infested areas in Wyoming, California, and Idaho, 900 to 1500 km (600 to 900 miles) to the north and northwest. Van Arsdel et al. (1998) argue that introduction by longdistance, aerial transport of aeciospores from pine to Ribes is more plausible than by transplanted, infected stock (either pine or Ribes). They cite how other rusts are observed to spread similar long distances. They also relate that the oldest rust cankers in the Sacramento Mountains predate the first recorded planting of white pine seedlings from Idaho and that the oldest cankers are far from the nearest home sites (where infected Ribes may have been planted). A study of the population genetics of WPBR conducted by R.C. Hamlin (personal communication) suggests the outbreak in the Sacramento Mountains resulted from a single introduction of inoculum from somewhere in western North America. His study found the rust in the Sacramento Mountains to have low genetic diversity (founder effect) and greater genetic similarity to other western populations than to eastern populations. Preliminary examination of regional air flow patterns into Arizona and New Mexico during the late spring suggests the origin of the rust was the southern Sierra Nevada where the rust has been established since the 1960s. The dispersal capacity of the rust in the southwestern United States is demonstrated by its spread throughout the Sacramento and adjacent White Mountains, into the Capitan Mountains, across a gap in host distribution of 50 km (30 miles), and to Gallinas Peak, a gap of 90 km (50 miles). Additional populations of southwestern white pine are located to the west in the Gila Mountains and to the northwest in the Magdalina and San Mateo Mountains (Little, 1971).

Association of pitch moths (Lepidoptera: Sesiidae and Pyralidae) with rust diseases in a lodgepole pine provenance trial

A survey in a lodgepole pine, Pinus contorta var. latifolia Engelm., provenance trial showed that the western pine moth, Dioryctria cambiicola (Dyar) (Lepidoptera: Pyralidae), was the most prevalent pitch moth, and stalactiform blister rust, Cronartium coleosporioides Arth., the most prevalent stem rust. Also present were the Douglas-fir pitch moth, Synanthedon novaroensis (Hy. Edwards) (Lepidoptera: Sesiidae), comandra blister rust, Cronartium comandrae Pk., and western gall rust, Endocronartium harknessii J.P. Moore, and the stem canker Atropellis piniphila (Weir). Results from a likelihood ratio test indicated an association of western pine moth with stalactiform blister rust and of Douglas-fir pitch moth with both western gall rust and stalactiform blister rust. Western pine moth attacks are most commonly found along the active edge of stalactiform blister rust cankers, suggesting that the moth larvae derive some specific benefit from the fungus. The association of Douglas-fir pitch moth with the rusts appear to be a result of the physical wounding caused by the fungi, since attacks by this pitch moth are also frequently found at pruning wounds or other injuries.

Development of comandra blister rust on lodgepole pine

The comandra blister rust parasite (Cronartiumcomandrae Pk.) causes a serious canker disease of lodgepole pine (Pinuscontorta Dougl. ex Loud. ssp. latifolia (Engelm.) Critch.) in the central Rocky Mountains. The expansion, longevity, and distribution of comandra blister rust cankers were studied by annual monitoring, reconstructing canker histories, and random sampling. In saplings, infections occur throughout the lower 80% of the crown; and branch cankers expand toward the bole at 2.5 cm•year−1, regardless of temperature, age, position, tree size, vigor, or susceptibility to infection. The proportion of branch cankers that develop into stem cankers decreases logistically both with distance from infection site to bole and with time since infection. Fewer than 50% of branch cankers that are farther than 20 cm from the bole or more than 8 years old are expected to establish stem cankers. The proportion of branch cankers that become stem cankers decreases with distance more rapidly for comandra blister rust than for other stem rusts. The mean height of stem cankers increases with total tree height, but cankers are uncommon at the top of the crown and low on the trunk of larger trees. The number of years for a canker to girdle its host equals the diameter of the stem at the center of the canker measured in centimetres. Because girdling cankers develop infrequently, slowly, and predictably, potential losses from comandra blister rust can be reduced by timely and appropriate removal of damaged trees.

Comparison of sample rules for estimating jack pine density, basal area, and percentage with sweetfern rust cankers

Sample rules that rate a cluster of trees at each sample point were investigated for performance in estimating the percentage of jack pine (Pinusbanksiana Lamb.) affected by cankers caused by sweetfern rust (Cronartiumcomptoniae Arth.). Performance for estimating the density and basal area of jack pine and cankered jack pine was also considered. Rule performance was rated with respect to efficiency in terms of the number of clusters or trees required for an adequate sample, bias, cluster size relative to optimal cluster size, and estimate precision.The types of rules included were fixed-area strip and circular plots, point samples, strips that include a constant number of trees, and rules based on point to tree distances. All rules appeared to provide unbiased estimates of the percentage of jack pine trees or basal area affected by sweetfern rust cankers. A cluster size of 18 was found to be optimal for such estimates with a confidence level of 80% and acceptable error size of E = ± 0.05. Optimal cluster size for other error factors and an efficient cluster size range were also identified. Only point sample and fixed-area rules appeared to be unbiased for density and basal area estimates. The best rule for all variables of interest was fixed-area strips with size adjusted to include an average of 18 jack pines per sample point.

Reduced growth, cull, and mortality of jack pine associated with sweetfern rust cankers

Analysis of a 13-stand sample from northern Ontario indicated that the sweetfern blister rust disease (Cronartiumcomptoniae Arth.) caused cankers that were associated with significantly reduced height, diameter, and volume growth of jack pine (Pinusbanksiana Lamb.). Cankered trees were smaller than unaffected jack pine by an average of 20% (range 0–40%) cubic volume and 29% (range 3–53%) board volume.The average size of cankered pines was reduced and directly related to the percentage in the stand that had severe cankers, as these trees seem to have a reduced capacity for competing with other trees. Size difference was negligible in several stands and this was explained as being due to the lack of competition in young stands and to the elimination of many severely cankered trees in older stands. Such trees are prone to domination by other trees and to attack by insects, fire, and wood rots.The merchantable volume of a cankered tree was reduced by about 11% because wood associated with cankers is distorted, resinous, and frequently has enclosed bark.Mortality of seedling-sized pines was not included in the study. Older trees seem to tolerate the presence of cankers, and mortality of these was confined mostly to dominated trees. Cankered pines had a greater tendency to become dominated and die than did unaffected pines, but mortality was considered unimportant because dominated trees add little in terms of stand competition or usable product.

Histology of Blister Rust Cankers Parasitized by Tuberculina maxima

Histology of Blister Rust Cankers Parasitized by Tuberculina maxima

INSECTS AND MITES ASSOCIATED WITH WESTERN WHITE PINE BLISTER RUST CANKERS IN IDAHO

AbstractInsects present in western white pine blister rust cankers in northern Idaho were: two weevils, Cylindrocopturus n. sp. and Pissodes sp. near swartzi Hopk.; two bark beetles, Pityophthorus sp. near nitidulus (Mann.), and Procryphalus ? sp.; a drosophilid fly, Paracacoxenus guttatus Hardy and Wheeler; and a phycitid moth, Dioryctria abietivorella (Grote). Mites associated with insect infestation were: Lasioseius ? n. sp., Ameroseius longitrichus Hirschmann, and Histiogaster arborsignis Woodring.

THE ARTHROPOD FAUNA COLLECTED FROM THE COMANDRA BLISTER RUST, CRONARTIUM COMANDRAE, ON LODGEPOLE PINE IN ALBERTA

AbstractOne hundred and sixty species of arthropods, representing 137 insects, 19 mites, and 4 spiders, were collected or reared from the cankers of the comandra blister rust, Cronartium comandrae Peck, on lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., in southwestern Alberta. The insects damaged 40 to 60% of the cankers observed in any one year and reduced aeciospore production by 10%. Eleven orders of insects were represented, of which the Coleoptera (29 species), Lepidoptera (14), Diptera (21), and Hymenoptera (38) were the most important. Epuraea obliquus Hatch, Paracacoxenus guttatus Hardy and Wheeler, and a Mycodiplosis species appeared to be true mycetobionts. Several others which damaged the cankers, such as Pissodes schwarzi Hopk., Cylindrocopturus deleoni Buchanan, Ernobius sp., Corticaria sp., Bradysia spp., Dioryctria spp., Laspeyresia sp., Grapholitha sp. prob. caeruleana Wlshm., Eucordylea spp., Cinara spp., and Diapterobates principalis (Berlese) could be classied as mycetophiles. About half the species appeared to be mycetoxenes. New habitat or host information was obtained and several new species were collected. Several of the genera represented have been reported to occur on other pine stem rusts, which indicates that the rust cankers provide a suitable habitat for development.

A Cage for Collecting Insects From Tree Stems and Branches

AbstractA lightweight and inexpensive cylindrical-sleeve insect cage is described. The cage was constructed of plastic screening and cotton fabric closed by an open-ended zipper. The cage was successfully used to collect insects from rust cankers on the stems and branches of pine trees.

Western gall rust cankers in Lodgepole Pine.

Western gall rust cankers in Lodgepole Pine.

The mechanical effect of fusiform rust cankers on stems of Loblolly Pine.

The mechanical effect of fusiform rust cankers on stems of Loblolly Pine.

A Dasyscypha Following Cronartium ribicola on Pinus monticola. II

SUMMARYA small-spored, white-excipled Dasyscypha frequently found associated with blister rust cankers on Pinus monticola in the northwestern United States has, in the past, been confused with D. Agassizii and D. calyciformis. Specimens of the three fungi were examined and their morphological features, hosts, geographical ranges, and parasitism were compared. In addition, cultural and pathological studies of the Dasyscypha on Pinus monticola were made.As a result, the fungus is considered distinct from D. Agassizii and D. calyciformis. In view of the fact that it was not possible to compare large numbers of collections of the three fungi on various hosts, both morphologically and culturally, the Dasyscypha on Pinus monticola was not proposed as a new species.