Cone Rust Research Articles

Cryptic Species Diversity and Phylogenetic Relationship in the Rust Genus Chrysomyxa from China.

Chrysomyxa rusts are fungal pathogens widely distributed in the Northern hemisphere, causing spruce needle and cone rust diseases, and they are responsible for significant economic losses in China. Taxonomic delimitation and precise species identification are difficult within this genus because some characters often overlap in several species. Adequate species delimitation, enhanced by the use of DNA-based methodologies, will help to establish well-supported species boundaries and enable the identification of cryptic species. Here, we explore the cryptic species diversity in the rust genus Chrysomyxa from China. Species delimitation analyses are conducted using a distance-based method (ABGD) and three tree-based methods (GMYC, bPTP, and mPTP) based on combined LSU and ITS sequences of over 60 specimens. Although there is some incongruence among species delimitation methods, two new species and three putative cryptic species are identified. The key to 20 Chrysomyxa species distributed in China is presented. These results suggest that a significant level of undiscovered cryptic diversity is likely to be found in Chrysomyxa from China. Future studies should consider multiple analytical methods when dealing with multi-locus datasets.

Temporal sporulation of Thekopsora areolata and Chrysomyxa spp. in Finnish Norway spruce seed orchards

Cone rusts Thekopsora areolata and Chrysomyxa pirolata are widely distributed in northern hemisphere. In Fennoscandia, these rusts cause severe damage and great economical losses especially in seed orchards specialized to produce high quality seeds. The aim of this study was to investigate sporulation of cone rusts and factors affecting epidemics to develop new control practices against these rusts. Natural sporulation of T. areolata was investigated in Finnish Norway spruce seed orchards on Prunus padus and the effect of environmental variables on rust sporulation in 2018–19. A sample of Prunus leaves was collected from which the coverage and number of T. areolata pustules were estimated. The frequency of cones with cone rusts, T. areolata, Chrysomyxa pirolata and C. ledi, was also estimated in Picea abies cones and the sporulation of C. pirolata on Pyrola sp. leaves in the seed orchards. The T. areolata incidence on Prunus was modelled with temperature sum, rainfall, seed orchard and time of estimation.The T. areolata disease incidence was low (<30%) in seed orchards in 2018, but it exceeded 100% in 2019. T. areolata pustules covered less than 10% of the leaves in 2018 and 10–40% in 2019. An ascomycete, Phloeosporella padi, was common in all Prunus leaves in 2018–19. Low rainfall in May-June explained the low disease rate on Prunus in 2018, while high rainfall explained the high disease rate in May-June in 2019. Cumulative rainfall, temperature sum, time and their interactions were all significant variables in a disease model explaining the disease incidence, while seed orchard was a non-significant variable. Cone rust frequency was low in P. abies cones in the seed orchards in 2019. Telia with basidia of C. pirolata were rare in May-June on Pyrola due to low rainfall in 2018, but frequent due to high rainfall in 2019. Rust control of T. areolata is recommended to concentrate on Prunus to reduce the number of overwintering diseased leaves in the seed orchards. Old infected cones should be removed from seed orchards to reduce aeciospore dissemination to Prunus in May-June. Control of C. pirolata is recommended to concentrate on Pyrola in early May.

Fruiting and sporulation of Thekopsora and Chrysomyxa cone rusts in Picea cones and Prunus leaves

SummaryNatural fruiting and sporulation of cone rusts were investigated in cones of Picea spp. and leaves of Prunus spp. in a botanical garden in northern Finland in 2007–2012. Thekopsora areolata was the most frequent cone rust in Picea abies cones, where it colonizes the host tissues and hinders normal seed development. Aecia of T. areolata were also common in cones of Picea engelmannii and occasionally in cones of P. glauca. Aecia of T. areolata sporulated in cones that were at least one year old. Chrysomyxa pirolata, another pathogenic cone rust, fruited and sporulated annually but infrequently in current‐year cones of P. abies. The spruce needle rust, Chrysomyxa ledi, fruited and sporulated commonly in current‐year cone scales of P. abies, P. omorika and P. glauca, while P. rubens, P. mariana and P. pungens appeared to be resistant during the study period. Chrysomyxa ledi did not affect seed development in infected cones. Uredinia of T. areolata frequently occurred on leaves of 41 Finnish and Russian cultivars, varieties or subspecies of Prunus padus L. ssp. badus and ssp. borealis and Pr. virginiana both in the botanical garden and in the field, while 13 exotic Prunus spp. lacked rust fruitbodies. All the Pr. padus cultivars were highly susceptible to T. areolata, thus, spreading the rust efficiently to surroundings. This is the first report of aecia of T. areolata in cones of P. engelmannii and P. glauca, and those of C. ledi in cones of P. omorika and P. glauca. Molecular identification confirmed the presence of T. areolata and C. pirolata on all hosts, and all samples of C. ledi belonged to the C. ledi‐rhododendri complex.

Thekopsora and Chrysomyxa cone rusts damage Norway spruce cones after a good cone crop in Finland

In 2006, an excellent crop of Norway spruce [Picea abies (L.) Karst] cones in Finland was severely damaged by rust fungi. The distribution and frequency of infection and the fruiting and sporulation of these rusts were investigated in 9 seed orchards and 23 seed tree stands in Finland. Thekopsora areolata (Fr.) Magnus was the most common and important cone rust that significantly reduced the seed crop of orchards in southern Finland, where infections were 10–89%. In northern Finland, the frequency of infected cones was much lower in seed tree stands (0–10%) than in seed orchards. Chrysomyxa pirolata Wint. occurred less frequently in most stands, but was more common in seed orchards. Chrysomyxa ledi (Alb. & Schw.) de Bary was the most frequent cone rust in seed tree stands of northern Finland. Thekopsora areolata colonized most or all of a cone and formed aecia on both adaxial and abaxial scales, while cone infections of C. pirolata were incomplete and sporulation took place only on the abaxial scale surface, as did C. ledi. Thekopsora areolata aecia failed to sporulate during the first year of cone formation, while aecia of both C. pirolata and C. ledi sporulated. Seed formation was significantly hampered and the seed crop significantly reduced by both T. areolata and C. pirolata.

(3Z,6Z,9Z,12Z,15Z)-Pentacosapentaene and (9Z,11E)-Tetradecadienyl Acetate: Attractant Lure Blend for Dioryctria ebeli (Lepidoptera: Pyralidae)

Feeding damage by larval coneworms (Lepidoptera: Pyralidae) on flowers and cones of pines can cause significant economic losses in pine seed orchards in the southern USA (Ebel et al. 1980, USDA Forest Service GTR SE-8, Asheville, NC). The south coastal coneworm, Dioryctria ebeli Mutuura & Monroe, is a common pest in seed orchards of slash pine (Pinus elliottii L.) in the coastal region of southeastern USA, particularly Florida (Ebel et al. 1980). With multiple generations per year, infestations of D. ebeli can be severe, especially in seed orchards infected by the southern pine cone rust, Cronartium strobilinum Hedgc. & Hahn (Merkel 1958, J. Forestry 56:651 ).

Seasonal fruiting and sporulation of Thekopsora and Chrysomyxa cone rusts in Norway spruce cones and alternate hosts in Finland

The need to improve control of cone rust epidemics led us to investigate seasonal fruiting and sporulation of cone rusts in Norway spruce ( Picea abies (L.) Karst.) cones and alternate hosts in 2006–2008. Spermogonia of Chrysomyxa pirolata Wint. and aecia of Thekopsora areolata (Fr.) Magnus developed in current-year cones in June, whereas C. pirolata aecia developed and started to sporulate in July. Thekopsora areolata aecia sporulated mainly in previous-year cones in May–August. Uredinia, telia, and basidia of C. pirolata developed in overwintered Pyrola sp. and Orthilia secunda L. leaves in May and sporulated in May–June. Uredinia of T. areolata developed in current-year Prunus padus L. leaves in June and sporulated in June–August. Telia of T. areolata developed in late summer, but no basidia were observed in overwintered Prunus padus leaves in March–May. Only minor variation occurred at the time of fruiting and sporulation of cone rusts both among cones and leaves of alternate hosts. Periods of high daily rainfall in May coincided with the epidemic peaks during female flowering in 2006. Dry periods in May coincided with high C. pirolata uredinia and low telia production on alternate hosts. However, monthly rainfall during pollination did not explain the epidemic rust patterns in cones. Timing of disease control is discussed.

Chrysomyxa pirolata G. Wint in Rabenh: New parasitic fungus on the cones and seeds of spruce

The new spruce disease known as "spruce cone rust" was discovered for the first time in Serbia and Montenegro. The fungus was detected in spruce forests only in the mountains regions (Kopaonik, Zlatar, Durmitor). This rust periodically damages the cones in localised forest areas and can be a serious problem. Usually seeds are not 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. As this disease is a serious problem, care must be taken to prevent the spread of the disease to the new uninfected regions.

Symptoms in slash pine seedlings following inoculation with the cone rust fungus Cronartium strobilinum

Six‐week‐old seedlings of slash pine (Pinus elliottii) were inoculated with sporidia of Cronartium strobilinum, which is the cause of southern cone rust disease, by wounding the apical tips of the seedlings. Pycnial sori developed abundantly within 1 month of inoculation on the epicotyl and primary needles. The progress of the pathogen was confirmed histologically within the cells of the stem and haustoria were observed near the nucleus of the cells. In the needles, pycnial pustules developed and the fungus was abundant in the mesophyll.

Evidence for environmental determination of uredinia and telia production in Chrysomyxa pirolata (inland spruce cone rust)

Chrysomyxa pirolata Wint., the cause of inland spruce cone rust, is a serious pathogen in natural spruce forests and seed orchards. Cone infection is caused by basidiospores produced by telia on alternate hosts in the genera Pyrola, Moneses, and Orthilia. The disease cycle of this rust and the influence of moisture on the differentiation of telia on Pyrola asarifolia Michx. were studied over two growing seasons at a wet site adjacent to a spruce seed orchard and a drier site adjacent to another orchard at Smoky Lake, Alberta, and at Edmonton and Hinton, Alberta. The proportion of uredinia to telia varied with microsite conditions, with more frequent production of telia in moist sites. The effect of moisture on formation of telia was tested by subjecting infected plants with immature sori to 90-100% relative humidity under various temperature and light conditions. Plants under high humidity, regardless of other conditions, formed mainly telia from immature sori, even if uredinia had already formed on parts of the leaves before the experiments. Telia formation, however, was much slower at 4-6°C than at 22°C. Cross-sections of sori showed that young uredinia could sometimes convert to telia. Results of a field experiment also suggested that increasing moisture increases the percentage of telia produced on plants. The production of undifferentiated sori that can become either uredinia or telia in response to environmental conditions may allow the fungus to maximize vegetative proliferation when conditions are unfavorable for sexual reproduction. It might also explain the large variation in cone rust levels from year to year in a given location.Key words: Picea, Pyrola, telia induction, seed orchard, Uredinales.

The infection of pyrola (Pyrola asarifolia; Pyrolaceae) by spruce cone rust (Chrysomyxa pirolata; Uredinales): Morphological correlates in the host and consequences for spore dispersal

Sexual spores (i.e., basidiospores) of the spruce cone rust (Chrysomyxa pirolata; Uredinales) produced on leaves of a small perennial herb, the common pink wintergreen (Pyrola asarifolia; Pyrolaceae), must travel from the forest floor to the forest canopy, where they infect the female cones of white spruce (Picea glauca; Pinaceae). Asexual spores (i.e., urediniospores) must move among pyrola plants on the forest floor. Spore transmission is complicated by relatively calm wind conditions within the forest, and the short critical period during which the cones of white spruce can be infected. Here, we document a correlation between the orientation of leaves in the pyrola and presence of rust pustules on the leaf’s ventral surface. We experimentally address the consequences to spore dispersal of this change in leaf position and presence of pustules. Transmission of rust spores can increase with higher leaf angles in two ways: (i) by raising the pustules further above the ground surface, thereby increasing the probability that wind will carry spores further (confirmed in experiment 1), or (ii) by increasing the probability that flying insects will alight on the pustules (confirmed in experiments 2 and 3), and either carry asexual spores (i.e., urediniospores) to other pyrola plants, or carry basidiospores to spruce cones. Vertical orientation increased insect attraction to both real and artificial leaves. Presence of rust increased insect attraction to natural leaves, an effect that could not be mimicked with coloured artificial leaves. Colour alone cannot explain attraction of insects (confirmed in experiments 2 and 3). We infer that both wind and flying insects, as potential agents of spore dispersal, are the likely targets of the rust’s alteration of the orientation and structure of the ventral surface of leaves of its pyrola host.

Evidence for environmental determination of uredinia and telia production in &lt;i&gt;Chrysomyxa pirolata&lt;/i&gt; (inland spruce cone rust)

Chrysomyxa pirolata Wint., the cause of inland spruce cone rust, is a serious pathogen in natural spruce forests and seed orchards. Cone infection is caused by basidiospores produced by telia on alternate hosts in the genera Pyrola, Moneses, and Orthilia. The disease cycle of this rust and the influence of moisture on the differentiation of telia on Pyrola asarifolia Michx. were studied over two growing seasons at a wet site adjacent to a spruce seed orchard and a drier site adjacent to another orchard at Smoky Lake, Alberta, and at Edmonton and Hinton, Alberta. The proportion of uredinia to telia varied with microsite conditions, with more frequent production of telia in moist sites. The effect of moisture on formation of telia was tested by subjecting infected plants with immature sori to 90-100% relative humidity under various temperature and light conditions. Plants under high humidity, regardless of other conditions, formed mainly telia from immature sori, even if uredinia had already formed on parts...

Evaluation of Aerial Applications of Acephate and Other Insecticides for Control of Cone and Seed Insects in Southern Pine Seed Orchards2

Acephate was evaluated for control of cone and seed insects in southern pine seed orchards from 1980 to 1985. Insecticides compared with acephate during this study were azinphosmethyl, fenvalerate, malathion, and the bacterium Bacillus thuringiensis. Insecticides were applied aerially, by hydraulic sprayers, and by airblast sprayers. Experiments were conducted in loblolly pine seed orchards in Florida and North Carolina and in two slash pine seed orchards in Florida. Control of coneworms, Dioryctria spp., slash pine flower thrips, Gnophothrips fuscus (Morgan), and two seed bugs, the leaffooted pine seed bug, Leptoglossus corculus (Say), and the shieldbacked pine seed bug, Tetyra bipunctata (Herrich-Schäffer) was evaluated. Frost damage and a serious infection of southern cone rust, Cronartium strobilinum (Arth.) Hedgc, and Hahn, caused significant flower and conelet losses and may have obscured differences between treatment effects during some years. All of the insecticide treatments were equally effective in controlling coneworms. The percentages of trees infested with pine tortoise scale, Toumeyella parvicornis (Cockerell), and the striped pine scale, T. pini (King), and the numbers of scale insects per branch after five applications of insecticide, differed significantly for acephate and fenvalerate treatments.

Management of pathogens in seed orchards and nurseries

The biology, damage and impact, and recent innovations in management of the major diseases affecting seed orchard trees and cones and forest nursery seedlings across Canada are discussed. Specific diseases covered are Armillaria root rot (A. ostoyae) and inland spruce cone rust (Chrysomyxa pirolata) in seed orchards, and damping-off and root rots, especially Cylindrocladium floridanum, and gray (Botrytis cinerea) and storage moulds of forest nursery seedlings. Areas needing research are also mentioned. Key words: Root rots, cone rust, damping-off, gray mould, storage moulds

Inland spruce cone rust of black spruce: Effect on cone and seed yield, and seed quality

AbstractThis paper is a follow‐up of an earlier article on inland spruce cone rust published by the author in 1981. It discusses the impact of the disease on cone and seed production, and seed quality, including seed viability. The cone and seed production and seed viability were reduced to a lesser or greater degree depending on the severity of infection; in severely infected cones practically no seeds were produced.

Inland spruce cone rust (Chrysomyxapirolata) control: relation of ferbam application to basidiospore production, rainfall, and cone phenology

Experiments were conducted over a 3-year period (1982–1984) at a white spruce (Piceaglauca (Moench) Voss) seed orchard near Salmon Arm, British Columbia, to relate the control of inland spruce cone rust (Chrysomyxapirolata Wint.) by ferbam to the number of fungicide applications, basidiospore production, rainfall, and cone phenology. Either multiple or single applications of ferbam during the period starting about 1 week before and through the pollination period reduced the incidence of the disease by 5- to 10-fold without any reduction in seed yield per cone, although seed germination was reduced slightly.

Inland spruce cone rust, Chrysomyxa pirolata, in Pyrola asarifolia and cones of Picea glauca, and morphology of the spore stages

Intact and sectioned specimens were examined by using a light and a scanning electron microscope to determine the presence and spore morphology of inland spruce cone rust, Chrysomyxa pirolata Wint., in Pyrola asarifolia Michx. plants and in white spruce, Picea glauca (Moench) Voss, cones. Field observations of rust development and sporulation were made throughout the year. The microscope studies confirmed that C. pirolata is systemic and perennial in shoots and connecting rhizomes of P. asarifolia, indicating that one mode of fungus spread is between plants originating from the same rhizome. Sometimes, hyphae of C. pirolata occurred only at the nodes along part of a rhizome connecting diseased P. asarifolia plants. Spring-collected buds from diseased P. asarifolia contained C. pirolata mycelium, but the fungus was not evident externally on current growth until the following spring. However, all leaves, especially those produced in the current year, on these plants were more upright and their upper surface less shiny. In some years, all P. asarifolia leaves in a locality bore mostly uredinia or telia; at other times about equal numbers of both were present on each leaf. About 6 weeks after telial production, spermogonia appeared on nearby spruce cones and about 4 weeks later these cones bore aeciospores on most scales of the systemically infected cones. Fruiting bodies and spores for each stage of the life cycle of the fungus are illustrated.

Mist-Blower Applications for Control of Flower Thrips and Southern Cone Rust in a Slash Pine Seed Orchard12

During 1967 and 1968, tests were conducted to determine if a flower thrips, Gnophothrips fuscus (Morgan), and southern cone rust, Cronartium strobilinum (Arthur) Hedgcock and Hahn, could be controlled with mist-blower applications of the fungicide ferbam combined with either malathion or heptachlor. Testing was done in a seed orchard of 8- and 9-year-old slash pine, Pinus elliottii Var. elliottii Engelmann, in northern Florida. Two applications of 0.25% heptachlor or 0.75% malathion effectively reduced thrips attacks on female strobili. Malathion was the most effective and reduced total thrips attacks by 75%, and thrips kill of strobili by more than 80%. Ferbam did not deter allacks by thrips. Ferbam protected artificially inoculated strobili from infection by C. strobilinum , but the feasibility of controlling southern cone rust with mist-blower applications of ferbam in seed orchards was not substantiated because of lack of natural infection. None of the treatments adversely affected total seed yields, full seed yields, or percentage full seed germination.

Studies of western tree rusts. VIII. Inoculation experiments with conifer needle rusts (Melampsoraceae)

Results from 22 cross-inoculation experiments provide confirmatory and new information on broom rusts of spruce and fir (Chrysomyxa arctostaphyli Diet. and Melampsorella caryophyllacearum Schroet.) and needle rusts of pine, larch, and fir (Coleosporium asterum (Diet.) Syd., Melampsora paradoxa Diet. &amp; Holw., Pucciniastrum epilobii Otth, Uredinopsis longimucronata Faull, U. phegopteridis Arth., and U. struthiopteridis Stoerm. ex Diet.). New host and distribution records are confirmed by inoculation. Cone rust of alpine fir is shown to be caused by Pucciniastrum epilobii. The need for further study of needle rust of pine (Coleosporium) and a monographic treatment of the willow rusts (Melampsora epitea complex) is suggested.

Some Aspects of the Biology and the Control of Southern Cone Rust

Some Aspects of the Biology and the Control of Southern Cone Rust

STUDIES OF WESTERN TREE RUSTS: I. A NEW CONE RUST ON SITKA SPRUCE

Local damage on the Queen Charlotte Islands to seed of Sitka spruce, Picea sitchensis, has led to the discovery of the causal agent, a new cone rust. At the same time a new Chrysomyxa on the one-flowered pyrola, Moneses uniflora, was discovered in the same area. Evidence from observations in the field, from controlled inoculations, and from the similarity of markings on aeciospores and urediniospores has led to the conclusion that the cone rust is the aecial stage of an undescribed Chrysomyxa. The rust has been described and named Chrysomyxa monesis. It is feared that the rust may cause serious damage to spruce seed abroad unless its spread is prevented. Surface sterilization of spruce seed before export is therefore recommended.