New hosts for Lecanosticta acicola and Dothistroma septosporum in newly established arboreta in Spain

A historical outbreak of needle blight disease was recorded during 2018 to 2019 in plantations of Pinus radiata and Pinus nigra in the North of Spain. The main pathogens involved in this historical outbreak were identified as Lecanosticta acicola and Dothistroma septosporum. Recently, a variety of tree species in three arboreta planted between 2011 and 2013 in the Basque Country as part of the European project REINFFORCE were showing symptoms of needle blight and defoliation. The aim of this study was to determine which pine species were affected with these pathogens. Tree species sampled included several provenances of P. brutia, P. elliottii, P. nigra, P. pinaster, P. pinea, P. ponderosa, P. sylvestris and P. taeda. Using molecular identification methods, Lecanosticta acicola was confirmed infecting Pinus brutia (Provenance: Alexandropolis, Greece and var. eldarica, Crimea) and represents a new host species for this pathogen. Pinus elliottii (Provenance: Georgia, USA) and P. ponderosa (Provenance: Central California, USA) are new host reports of L. acicola for Spain. Dothistroma septosporum was found for the first time on P. brutia (Provenance: Marmaris, Turkey) and P. ponderosa (Provenance: Oregon, USA) in Spain and was also detected infecting P. nigra (Provenance: Sologne Vayrières, France).     

Fire resistance of European pines

Pine resistance to low- to moderate-intensity fire arises from traits (namely related to tissue insulation from heat) that enable tree survival. Predictive models of the likelihood of tree mortality after fire are quite valuable to assist decision-making after wildfire and to plan prescribed burning. Data and models pertaining to the survival of European pines following fire are reviewed. The type and quality of the current information on fire resistance of the various European species is quite variable. Data from low-intensity fire experiments or regimes is comparatively abundant for Pinus pinaster and Pinus sylvestris, while tree survival after wildfire has been modelled for Pinus pinea and Pinus halepensis. P. pinaster and P. pinea, and Pinus canariensis in special, are better equipped to survive fire, but low-intensity fire is tolerated even by species often referred to as fire-sensitive (P. halepensis and Pinus radiata). The relative fire resistance of European pine species is assessed on the basis of (i) morphological and experimental data, and (ii) mortality modelling that considers fire behaviour. Limitations of these approaches to rate fire resistance are discussed, and the current knowledge gaps are indicated.     

Environmentally induced changes in the distribution of disease susceptibility phenotypes in Pinus radiata

Pinus radiata (Monterey pine) is highly susceptible to Fusarium circinatum, the cause of pitch canker, but heritable variation in resistance to this disease has been documented in P. radiata. In this study, the distribution of susceptibility phenotypes (=lesion lengths) was assessed by inoculating P. radiata trees with a spore suspension of F. circinatum. The results show the distribution of susceptibility phenotypes in naïve seedlings to be normally distributed, both in a breeding population and in a population established from seed collected in a native forest. This pattern aligns with expectations for a quantitatively inherited trait. However, after 2.5 years of growth in a forest, variation in susceptibility is no longer normally distributed but rather is positively skewed. Thus, exposure to the forest environment results in a distribution that is enriched for relatively resistant individuals. A similarly skewed distribution is observed in standing trees in a native population of P. radiata. The observed change in distribution cannot be attributed to ontological effects on resistance to pitch canker, because tree age accounts for almost none of the variation in susceptibility. We hypothesize that the change in distribution of susceptibility phenotypes is due primarily to infections and infection attempts by the microbiota resident in the forest.     

The relationship between terpenes and flammability of leaf litter

Many studies have assumed that plant terpenes favor fire due to their enormous flammability. However, only a few of them, all performed on green leaves, have demonstrated this. In the present work we investigated the question of whether litter terpene content can be used to estimate flammability and temperatures reached during fire. Epiradiator and burn table tests were used to compare flammability of leaf litter of P. pinaster, P. halepensis, P. pinea, C. albidus, C. ladanifer, C. laurifolius and the mixture of litter of P. pinaster with that of the other five species (e.g. P. pinaster + P. halepensis). Tests with burn table showed increasing spread rates and shorter combustion times under higher terpene contents. Flame height was triggered both with higher a terpene content and bed thickness, whereas the percentage of burned biomass was only significantly correlated to bed height. Epiradiator tests indicated that terpene concentration in leaf litter was positively correlated to flame height and negatively correlated to both flame residence time and ignition delay. Flammability was high for P. pinaster, P. halepensis, and hence for P. pinaster + P. halepensis, intermediate for C. albidus, P. pinea and P. pinaster combined with each of these species, and low for C. laurifolius, C. ladanifer and P. pinaster combined with them. Accordingly, their terpene content was high, intermediate and low. We concluded that plants might influence fire intensity, by having stored terpenes in their dead leaves, in addition to having developed traits to survive fire. Thus, a correct management of dead aboveground fuels rich in terpene concentrations, such as those of P. pinaster and P. halepensis, could prove helpful in reducing the hazard of fire.     

Sphaeropsis shoot blight and altered nutrition in red pine plantations treated with paper mill waste sludge

During 1993 progressive, severe shoot blight and canker disease in crowns of mature, merchantable red pines (Pinus resinosa) in central Wisconsin was noted in plantations in which paper mill waste sludge previously had been applied. For eight treated plantations and six non‐treated plantations, incidence of shoot blight attributed to the pathogenic fungus Sphaeropsis sapinea (syn. Diplodia pinea) was quantified during 1993 or 1994. Foliage and soil samples also were collected for analyses. Sphaeropsis shoot blight was more frequent in treated plantations than in the non‐treated stands (means of 81% of trees and 10.2% of shoots compared with 7% of trees and 0.1% of shoots, respectively). Consistent with other reports of damage caused by some diseases of conifers in situations of altered host nutrition, mean foliar N concentrations were higher in treated plantations (1.61%) than non‐treated plantations (1.31%) (p < 0.001). Mean foliar Zn, Mn, Cu, and Al concentrations were lower in treated plantations than non‐treated plantations, and mean soil P, Ca, and Mg concentrations were higher in treated plantations than non‐treated plantations.     

Exposure to a pine pathogen enhances growth and disease resistance in Pinus radiata seedlings

Most studies of Fusarium circinatum, the cause of pitch canker in pines, have focused on its activity as a pathogen. However, recent findings indicate that this fungus can colonize roots of Pinus radiata without inducing symptoms. Contrary to expectations, this study revealed that seedlings grown in infested sand grew more rapidly than seedlings not exposed to F. circinatum, based on root and shoot biomass, with modifications to root system architecture, including increased mycorrhizal root development. These effects were dependent on inoculum density and duration following growth in infested rooting medium. Plants exposed to F. circinatum expressed elevated resistance to stem infections, which significantly decreased the incidence of mortality; as above, effects were dependent on inoculum density. Resistance to stem infections was also enhanced in seedlings that emerged through infested litter, as occurs in native stands. Beneficial to neutral interactions of F. circinatum with its host suggest that the life history of this fungus may be more complex than previously recognized, with activities similar to non‐pathogenic endophytes. The potential for non‐lethal infections by F. circinatum to induce resistance in seedlings may influence dynamics of stand establishment. Overall, these results indicate that pathogenic organisms with asymptomatic states may have cryptic ecological functions that extend beyond the impacts of disease.     

Risk from Sirococcus conigenus to understory red pine seedlings in northern Wisconsin

Interest in development of multicohort stands of red pine (Pinus resinosa) in the Great Lakes region of North America prompted an investigation of the potential impact of the shoot blight pathogen Sirococcus conigenus (syn. S. strobilinus) on understory red pine seedlings. In May 2002 and 2003 healthy, 1‐year‐old red pine seedlings were planted in the understory of a maturing red pine plantation in northern Wisconsin in an area with a history of presence of this pathogen. Occurrence of shoot blight symptoms was recorded periodically during the summer, and in each year seedlings were harvested in fall and examined for signs of shoot blight pathogens. By fall 2002 and 2003, respectively, shoot blight incidence was 89% and 98% and most seedlings were dying. Pycnidia with conidia of S. conigenus were present on almost all of the symptomatic seedlings. The conifer shoot blight and canker pathogen Diplodia pinea (syn. Sphaeropsis sapinea) was also detected, though less frequently. Pycnidia of S. conigenus tended to be found more frequently on symptomatic current year's shoots than symptomatic previous year's shoots; the opposite was true for pycnidia of D. pinea. Risk from S. conigenus to understory red pine seedlings should be considered in any plans for development of multicohort red pine stands in areas where the pathogen is present.     

Excised shoots of top-pruned red pine seedlings,a source of inoculum of the Diplodia blight pathogen

Diplodia pinea causes shoot blight and collar rot diseases of pines in forest tree nurseries and sporulates on colonized seedling needles and stems. In late summer 2005, pycnidia of D. pinea were observed on shoots that had been excised by top pruning red pine seedlings earlier that summer during the third season of growth. This observation prompted surveys to determine the incidence and abundance of D. pinea conidia on excised shoots. At each of two nurseries, excised shoots were collected from the seedling canopy and adjacent alleyway soil in two subplots in each of five beds (plots). Excised shoots from both nurseries bore pycnidia with conidia of D. pinea. A water washing and filtration technique was used to quantify D. pinea conidia extracted from these shoots. Excised shoots collected from the seedling canopy yielded more D. pinea conidia than shoots collected from adjacent alleyway soil. Collection and removal of excised shoots resulting from top pruning of pine nursery seedlings should be considered as a means of reducing inoculum in areas where D. pinea is present.     

Susceptibility of six pine species to Gremmeniella abietina isolates from Spain

Inoculation experiments were performed in order to evaluate the virulence of Gremmeniella abietina isolates from Spain on the main pine species planted in the Iberian Peninsula, as well as the influence of seedling age on this virulence. Two different experiments were carried out with four isolates of G. abietina from Spain. The greenhouse experiments consisted of seedling inoculations. One‐ and 2‐year‐old seedlings of the following five pine species were used: Pinus halepensis, Pinus pinea, Pinus pinaster, Pinus sylvestris and Pinus uncinata; also, 1‐year‐old seedlings of P. nigra were inoculated. The relative necrosis length (RNL) caused by the pathogen after 130 days was used as a response variable. The laboratory experiments were performed on 2‐ to 6‐year‐old internodes of the above pine species excluding P. uncinata. The necrosis length after 6 weeks of incubation was measured. The results have shown that all G. abietina isolates were pathogens on seedlings of these six pine species and seedlings of P. halepensis were consistently the most susceptible ones, although it is important to take into account that all the isolates used in the present work were isolated from P. halepensis, the only pine species in Spain where G. abietina has been recovered up to now. The susceptibility of the other pine species depended on the age of the seedlings.     

Root and butt rot caused by Heterobasidion annosum in Atlantic coniferous ecosystems of Spain

In the second half of the 20th century, the forested surface in northern Spain started to increase during a process of reforestation and the replacement of native forest. This reforestation was performed mostly by introducing monocultures of exotic coniferous species. One of the implications of intense forest exploitation and the introduction of new forest species is an increase in disease outbreaks. Because the genus Heterobasidion includes some of the most significant conifer pathogens in the world, surveys were conducted to collect and identify H eterobasidion isolates associated with diverse hosts within coniferous forests and plantations in the Basque Country, northern Spain. A total of 159 stands were surveyed, and 45 isolates were obtained from different trees. Based on sequencing of the internal transcribed spacer region of the ribosomal DNA, all collected isolates were identified as European H eterobasidion annosum s.s. (European P‐type). Heterobasidion annosum was detected in 28.3% of the sampled stands, with the following distribution by host: Chamaecyparis lawsoniana (11.1%), P inus pinaster (2.2%), P . radiata (42.2%), P . nigra (2.2%), P . sylvestris (17.8%), P seudotsuga menziesii (17.8%) and P icea abies (6.7%). The spatial distribution of the population showed a high degree of clustering. This is the first report of H . annosum s.s. causing damage to forest plantations of Chamaecyparis lawsoniana, P inus pinaster, P . radiata, P seudotsuga menziesii and P icea abies in Spain. In the current context of forest pathosystems, the management practice of replacing susceptible forest species with resistant species is recommended.     

Site-related influences on cone-borne inoculum and asymptomatic persistence of Diplodia shoot blight fungi on or in mature red pines

The shoot blight and canker pathogens Diplodia pinea and D. scrobiculata sporulate abundantly on cones of many pine hosts. Variation in incidence and abundance of potential inoculum from cones and frequency of asymptomatic persistence on or in shoots was examined for mature red pines in sites differing in dominant presettlement vegetation and soil type in Bayfield and Douglas counties in northern Wisconsin. Collections were made in each county from 6 plantations, 3 each in areas historically vegetated with jack pine and soils mapped as sands and three in areas historically vegetated with red pine with soils mapped as loamy sands. At each site, 5 cones were collected from each of 5 red pines and 10 shoots were collected from up to 5 red pines. Conidia from cones were quantified with a water wash and filtration technique. Diplodia species were cultured from surface-disinfested asymptomatic shoots. A species-specific PCR assay was used to identify the Diplodia species from cones and shoots. Although cones and asymptomatic shoots from each county yielded D. pinea and D. scrobiculata, D. pinea was detected more frequently. More conidia were obtained from cones from Douglas Co., where there is a history of severe shoot blight damage, than cones from Bayfield Co. In Douglas Co., more conidia were obtained from cones from plantations in areas of more sandy soil and presettlement jack pine dominance than cones from plantations in areas of less sandy soil and presettlement red pine dominance. The numbers of conidia and frequencies of cultural detection of Diplodia species from asymptomatic shoots at a site were positively correlated. These results provide evidence for site-related influences on abundance of pathogen inoculum and asymptomatic persistence on or in red pine crowns that may contribute to differences in frequency and severity of damage from Diplodia shoot blight.     

Evaluation of Pinus radiata seed treatments to control Fusarium circinatum: effects on seed emergence and disease incidence

In this study, the effects of hot water (HWT), hydrogen peroxide and fungicides on the incidence of Fusarium circinatum on artificially inoculated Pinus radiata seeds were evaluated. Fifteen commercial fungicide formulations were screened in vitro for inhibitory activity on mycelial growth and conidial germination of F. circinatum. With half‐maximal effective concentration (EC₅₀) lower than 0.5 ppm, fluazinam, imazalil and tebuconazole were the most effective fungicides on mycelial growth, while captan, mancozeb or pyraclostrobin were the most effective (EC₅₀ < 0.3 ppm) on conidial germination. Based on the results obtained, imazalil, fluazinam, mancozeb and pyraclostrobin were selected for further testing. The effects of HWT, hydrogen peroxide and fungicide treatments on seed emergence and the incidence of F. circinatum were assessed. Seed treatments with fungicides prior to sowing were less effective and inconsistent in reducing the incidence of F. circinatum on seedlings. In contrast, hot water and hydrogen peroxide treatments significantly reduced F. circinatum contamination on P. radiata seeds with an overall disease incidence lower than 0.8% on seedlings. Furthermore, subsequent application of fungicides on seedlings did not improve the effectiveness of HWT. These results, therefore, suggest that hot water is a better alternative to hydrogen peroxide and fungicides as Pinus seed treatment against F. circinatum and could easily be implemented as standard in commercial nurseries to control the spread of the pitch canker disease.     

Chitosan as a biocontrol agent against the pinewood nematode (Bursaphelenchus xylophilus)

The pine wilt disease (PWD) is caused by Bursaphelenchus xylophilus and poses great environmental and economic challenges. Thus, the development of sustainable techniques for the control of this epidemic disease is of major importance. This work aimed at evaluating if the application of different molecular weight (MW) chitosans as a soil amendment could be used to control the PWD in maritime pine (Pinus pinaster, very susceptible to the disease) and stone pine (Pinus pinea, less susceptible). At the end of the experimental period (24 days after inoculation), P. pinaster and P. pinea untreated plants presented ca. 3825 ± 100 and 70 ± 47 nematodes, respectively. In P. pinaster, the high‐MW chitosan prompted the most drastic results, inducing a 21.9‐fold reduction in nematodes numbers, whereas in P. pinea, the most effective was the low MW chitosan, which reduced nematodes numbers up to 7‐fold, compared with untreated plants. P. pinea seems to be highly resistant to the disease, presenting nematode numbers up to 54.6‐fold lower than P. pinaster and less severe chlorophyll loss (ca. 2‐fold).     

Diplodia shoot blight and asymptomatic persistence of Diplodia pinea on or in stems of jack pine nursery seedlings

Diplodia pinea (syn. Sphaeropsis sapinea) is known as a major cause of damage to red pine (Pinus resinosa) seedlings in nurseries. The fungus can also be a latent pathogen of red pine seedlings, persisting in the absence of gross symptoms and later proliferating under conditions that induce host stress. In the fall of 2004, three nurseries in Wisconsin were surveyed to determine the potential for the occurrence of Diplodia shoot blight on jack pine (Pinus banksiana) seedlings and the persistence of D. pinea on or in asymptomatic seedlings of this species. Incidence of shoot blight was quantified in five 1 m long segments of an interior row in each of two survey areas in each nursery. The pathogen was identified on symptomatic seedlings collected in these areas on the basis of presence of characteristic pycnidia and conidia. Five groups of 20 asymptomatic seedlings were also collected in each of the two survey areas in each nursery. A segment of the lower stem/root collar from each of these asymptomatic seedlings was surface‐disinfested and culturally assayed using tannic acid agar. The mean incidence of shoot blight (as high as 9%) and mean frequency of cultural detection from asymptomatic seedlings (as high as 20%) were greatest in proximity to red pine windbreaks which are a source of inoculum. Only D. pinea was confirmed from subsets of symptomatic and asymptomatic seedlings which were tested using mt SSU rDNA polymerase chain reaction (PCR) primers that allow differentiation of D. pinea from D. scrobiculata and other fungi in the genus Botryosphaeria and related anamorphic fungi. Jack pine seedlings inoculated with D. pinea isolates obtained from asymptomatic nursery seedlings developed shoot blight symptoms in greenhouse trials. Thus, the ability of D. pinea to damage jack pine seedlings in nurseries has been documented and the potential for virulent strains of this latent pathogen to be distributed on asymptomatic jack pine seedlings from nurseries has been confirmed.     

Histology of Diplodia pinea in diseased and latently infected Pinus nigra shoots

Diplodia tip blight is a serious disease of >30 conifer species worldwide. Symptoms are particularly severe on non‐native, two‐needled Pinus species, and typically include stunted, necrotic needles and shoots and a general decline of the tree. Latent Diplodia pinea infections occur in current‐year shoots of some symptomless pines, and in some apparently healthy current‐year shoots of diseased pines. Latent infections also occur in symptomless terminal buds. A histological approach was used to investigate the nature of latent infections in shoot stems and terminal buds of landscape Pinus nigra. Fungal colonization was compared in healthy, diseased and latently infected tissues. A nested‐PCR technique that is specific for D. pinea was used to differentiate latently infected tissues from uninfected ones. Latent D. pinea infections were localized in the outer stem cortex, usually in the vicinity of needle scales at leaf axes. In contrast, pathogenic D. pinea infections were characterized by fungal colonization throughout the shoot stem tissues, even very early in symptom development. The presence of necrophylatic periderms in two of the latently infected samples suggests that host defences play a role in the production and maintenance of latent stem infections. Latent infections of terminal buds appeared to originate from the distal bud scales of axillary buds in the terminal bud cluster, and not from the subtending shoot. Fungal tissues were never observed inside asymptomatic, PCR‐negative shoots.     

Sphaeropsis canker,a new disease of cypress in Greece

The fungus Sphaeropsis sp. is reported for first time in Greece to cause cankers on Cupressus sempervirens. The cultural characteristics on PDA, spore shape and size and canker morphology were identical to those of the fungus described as Diplodia pinea f. sp. cupressi in Israel. The cankers of Sphaeropsis sp. are characterized by resin exudation, with fissuring of the bark over a dry sector of the wood. The pathogenicity of the Sphaeropsis sp. was proved by artificial inoculations on selected cypress clones resistant and susceptible to Seiridium cardinale. The mean canker length of the susceptible clone was significantly more than that of the resistant clones. It appears that the defence reaction in cypress against both fungi is similar. In artificial inoculations on Pinus halepensis and Pinus pinea, Sphaeropsis sp. was nonpathogenic. During a 3‐year period, in an experimental plot in western Peloponnese, the fungus spread from one, initially, to 13 cypress clones. Drought stress during the summer appears to be the main factor predisposing the cypress plants to become susceptible to the fungus.     

Variation in susceptibility of six pine species and hybrids to pitch canker caused by Fusarium circinatum

Six pine species or hybrids were tested for susceptibility to pitch canker caused by Fusarium  circinatum. Pinus  densiflora, Pinus  thunbergii, Pinus  x rigitaeda (Pinus  rigida × Pinus  taeda), P. rigida × P. x rigitaeda, Pinus  echinata and Pinus  virginiana were inoculated with three spore loads (50, 500 and 5000 per tree) of F. circinatum. External symptoms, lesion length, and the frequency of reisolation of the fungus were investigated. External symptoms were greatest in P. echinata, followed by P. virginiana, however, P. densiflora was not susceptible to F. circinatum. Based on mean lesion lengths, the six pine species or hybrids differed significantly (p < 0.01) in susceptibility to pitch canker. Pinus  echinata sustained the longest lesions, whereas P. densiflora sustained the shortest lesions. The effect of inoculum density was not significant among three spore treatments within species (p = 0.17), although lesion length was slightly greater at higher spore loads over all pine species. The fungus was reisolated from inoculated stems of all pine species tested, even on trees showing little or no damage from the disease. Additional studies are needed to further explore the basis for resistance to pitch canker.     

Variation in pitch canker resistance among provenances of <Emphasis Type="Italic">Pinus patula</Emphasis> and <Emphasis Type="Italic">Pinus tecunumanii</Emphasis> from Mexico and Central America

Pinus patula and high-elevation (HE) sources of P. tecunumanii exhibit intermediate levels of resistance to pitch canker (Fusarium circinatum), compared to extremely resistant species such as P. oocarpa, and extremely susceptible species such as P. radiata. Seedlings from 20 P. patula provenances and 15 HE P. tecunumanii provenances were artificially inoculated with the pitch canker fungus at 21 and 12 weeks of age, respectively, and assessed for resistance 12–20 weeks later. There was important provenance variation in pitch canker resistance for both species. The 20-week LiveStem percentage ranged from 70.3% to 43.6% among the P. patula provenances and 59.6% to 11.7% among HE P. tecunumanii provenances. There was a geographic pattern to the provenance variation, and in both species, low altitude sources demonstrated more resistance than those from high elevation. Provenance variation in pitch canker resistance could be useful when making selection and breeding decisions with these species.     

High genetic diversity of Fusarium circinatum associated with the first outbreak of pitch canker on Pinus patula in South Africa

The disease known as pitch canker results from infection of Pinus species by the fungus Fusarium circinatum. This fungus also causes a serious root disease of Pinus seedlings and cuttings in forestry nurseries. Pinus radiata and P. patula are especially susceptible to the pathogen, but there are no records of pitch canker on P. patula in established plantations. To date, only planting material of this tree species in nurseries or in plantations at the time of establishment have been infected by F. circinatum. Symptoms of pitch canker have recently emerged in an established P. patula plantation in South Africa and this study sought to determine whether the symptoms were caused by F. circinatum. Isolates from cankers were identified as F. circinatum using morphology and DNA-based diagnostic markers. Microsatellite markers were then used to determine the genetic diversity of a collection of 52 isolates. The entire population included 17 genotypes representing 30 alleles, with a greater number of genotypes collected from younger (three- to six-year-old) than older (12- to 19-year-old) trees. Both mating types of F. circinatum were present, but no evidence of sexual recombination was inferred from population genetic analyses. This is the first record globally of pitch canker on P. patula trees in managed plantations. It is of significant concern to South Africa, where P. patula is the most important Pinus species utilised for plantation forestry.     

Assessment of molecular detection of Fusarium circinatum in insects and passive spore traps in Pinus radiata plantations

Fusarium circinatum is the causal agent of pitch canker, a destructive disease that threatens natural and planted pine forests around the world. Although pitch canker has caused problems in Spain and Portugal, concerning Europe as a whole, the fungus is not established across the pine distribution area. Its dispersion by wind and/or insect vectors could nevertheless play a role in the colonization of currently uninfected stands. It is therefore crucial to develop monitoring tools for its detection. To this end, we assessed the molecular detection of the pathogen in environmental samples of bark beetles and passive spore traps, collected in two infected Pinus radiata plantations in Basque country, Spain. The spread pattern of F. circinatum was assessed by an experimental design that included insect and spore traps installed at the centre, at the edge and outside the plots. Our results showed that F. circinatum was detected in both types of samples, at almost all collection dates. In both type of samples, positive detections were mainly found at the centre of the plots, a lower proportion at the edge, and very few outside. This suggests that long‐distance dispersion of Fusarium circinatum does not rely on wind spore dispersal neither on insect flight. Our study also shows that molecular methods are a powerful tool to monitor the pathogen in environmental samples.