Sirococcus conigenus (DC.) Cannon & Minter (= S. strobilinus G. Preuss; Sys. Ascochyta piniperda Lindau; Septoria parasitica Hartig) can cause shoot blight of conifers, e.g. Norway spruce (Picea abies) and Scots pine ( Pinus sylvestris) (O`Brien, 1973; Shahin et al., 1978; Funk, 1972 and Wall et al., 1976); damping-off and dieback (Richard and Smith, 1973) as well as seedborne disease (Motta et al., 1993; Sutherland et al., 1980). It is one fungus of Coelomycetes, deuteromycotina and was firstly observed and reported by Hartig (1894) in Germany.
The disease occurs widely in nurseries, plantations, natural forests as well as ornamental trees. The plants commonly damaged by the fungus are western hemlock, reffreg, ponderosa, and red pines; blue and sitka spruces; Douglas-fir, white fir; eastern and European larches; Aleppo coulter, jack, Scots, sugar and ahitebark pines; and black, Engelman, Norway, red, and white spruces (Sinclair et al., 1987). This fungus was found mostly in Europe and part of Canada and USA. In Britain it has been recorded on seedlings of lodgepole pine (Pinus contorata) (Redfern et al., 1976) and as saprophyte on its cones (Ellis and Ellis, 1985). In Czech Republic, S. conigenus was found on blue spruce (Picea pangens) which resulted a high level infection incidence in the regions of air pollution (Soukup, 1994). The fungus in Austria, as a causal agent of shoot dieback of young Picea abies has been studied on its diseased symptoms in color change of the foliage as well as its distribution of affected sites in the country (Cech and Perny, 1995). In Finland, Kujala (1950) has found the fungus mostly in shoots of young spruce. The recent survey, however, shows that the fungus has a wide occurrence in center Finland and mostly can be found on spruce cones, diseased spruce shoots and also in Scots pine seedlings ( Råback, 1996). The intraspecies variation is not known. Peace (1962) suggested that the fungus on pine might be different variety from that on spruce. The similar opinion has been proven by O`Brien (1973). Illingworth (1973) studied lodgepole pine shoot blight in British Columbia and pointed the variation in disease incidence among provenance was under some genetic control and concluded that in susceptibility to S. conigenus a genetically-based geographic variation existed.
S. conigenus can infect young seedlings in the early summer at the base or the middle of the current shoots, where the needles turn brown and shrink, and soon fall. The disease tends to spread upwards from lower needles towards the ends of shoots and some movements may also take place downwards into the shoots of previous year's growth, leading to death of some of side shoots (Hartig, 1894). For a time the shoots tips remain green, but later wilt, droop and finally die, often curling over and assuming the shepherds´crooks (Funk, 1972). The fungus also severely infects large trees in forest stands. For example 21-meter-high red pine (Pinus reisinosa) was infected by the fungus and the disease spread upwards in the crown from the basal branches, while young trees sheltered below the large ones also were infected and killed (O´Brien, 1973). The current knowledge of S. conigenus as a severe seed-borne disease in Picea spp and other coniferous trees, was proven by the systematic studies. Sutherland et al. (1981) studied the disease on container-grown seedlings in British Columbia and found the fungus was seed-borne and the disease seed-transmitted in stika, white and Engelmann spruce and in the hybrid between the last. However no evidence was obtained to explain how the pathogen had entered seeds and it was not observed in seed coats.
In late summer, on plants affected by S. conigenus produce dark-brown or black, usually uni- or multiocular pycnidia erumpenting on necrotic tissues of infected shoots and vesicles. Mature pycnidia are semi-immersed with size of 90-120 mm diam. (Shahin and Claflin, 1978). They are also found on spruce cones and bud scales (Sinclair et al., 1978). Conidiophores hyaline, septate, filiform, broader at base, arising from the inner layer cells of pycnidia (Taxon, 1983). Conidia emerging from irregular openings of the fructification are fusiform, 1-septum, 12 -16 x 3 mm (Ellis and Ellis, 1985), occasionally 2-septate (Taxon 32, 1983). Hypha is hyaline and sparsely forked and arial felty-woolly mycelia are yellowish in malt agar.
The disease cycle is completed in 1 year and the fungus over winters on dead shoots and spruce cone scales (Sinclair et al., 1978). The fungal conidia were liberated in wet weather and dispersed by rain splash to nearby tissues of hosts. In most cases spring or autumn frosts can significantly promote the fungus to infect current-year shoots (Hartig, 1894 ).
The fungus is favored by mild temperature, wet weather and low light intensities (Wall and Magasi, 1976). The fungal germination occurs at temperature ranging from 10 to 32°C ( Shahin and Claflin, 1978). A daily temperature cycle of 16-21°C and low light intensities (900-3900 x) could create a great infection and 100% relative humidity in plastic bags could reach high infection (Wall and Magasi, 1976; Richard and Smith, 1973). Hamelin and Sutherland (1991) found the provenance of the fungus from dry interior had significantly lower disease incidence than those from the interior of wet belt.
Some researchers have studied abundant works in fungal morphology and its pathogenicity. But the pathogenicity was various in different hosts and age of intraspecies. In lodgepole pine exists genetically-based geographic variation in susceptibility to the fungus (Illingworth, 1973). The genetic variation between different regional species is not known. The processing to the fungus infect spruce cones and how to transfer disease to seeds are still unclear.
The noticed new kind of damping-off disease and its high occurrence in center Finland give us a motive to study more about this fungus. The aim of this study is to describe the characteristics of the fungus, and its pathogenicity to spruce and pine seedlings in the conditions of center Finland as well as the processing of the fungal infection to spruce cones.
Cech, TL and Perny, B., 1995: Pucciniastrum areolatum (Alb. et Schw) Liro (Uredinales) and other microfungi in connection with top dying of young Norway spruce (Picea abies (L. ) Karst. ). FBVA-Berichte. No. 88. 5-27
Funk, A., 1972: Sirococcus shoot-blight of western hemlock in British Columbia and Alaska. Plant Dis. Reptr. 56: 645-647
Hamelin, RC. and Sutherland, JR., 1991: Variation in the susceptibility of lodgepole pine provenance to Sirococcus shoot blight: results from artificial inoculations. Eur. J. For. Path. 21:3. 189-192
Illingworth, K., 1973: Variation in the susceptibility of lodgepole pine provenance to Sirococcus shoot blight. Can. J. For. Res. 3: 585-589
Kujala, V., 1950: Uber die kleinpilze der koniferen in Finland. Commun. Inst. Forest. Fenn. 38 (4): 62-63
Kliejunas, J., 1989: Fungicides for control of Sirococcus tip blight of pine at northern California nursery. Tree planters´notes. 1989. 40:2: 30-2
Korhonen, K. and Hintikka, V., 1980: Simple isolation and inoculation methods for fungal culture. Karstenia. 20: 19-22
Magasi, L. P.; Manley, S. and Wall, R. E., 1975: Sirococcus strobilinus, a new disease of spruce seedlings in Maritime nurseries. Plant Dis. Reptr. 59: 664
Motta, E.; Annesi, T and Forti, E., 1993: First report of Sirococcus conigenus seedborne in Norway spruce. Plant Dis. 77: 1169
O´Brien, J. T., 1973: Sirococcus shoot blight of red pine. Plant Dis. Reptr.57: 246-247
Osswald, WF,; Blaurock, B.; Herrgesell, E.; Geibel, M. R.; Treutter, D. and Feucht, W., 1994: The occurrence of picein and p-hydroxyaletophenone in spruce needles and the effect of the monoohenol on the growth of different forest pathogens. International symposium on natural phenols in plant resistances, Volume II, Weihenstephan, Germany. 13-17 Sep. 1993. Acta-Horticulture. No. 381. 548-556
Peace, T. R., (1962): Pathology of trees and shrubs. Clarendon Press. Oxford
Phillips, D. H. and Burdekin, D. A., 1992: Diseases of forest and ornamental trees. The Macmillan Press Ltd. 141-2, 173-4
Richard, S. and Smith, Jr., 1973: Sirococcus tip dieback of pine spp. in California forest nurseries. Plant Dis. Reptr. 57: 69-73
Shahin, E. A. and Claflin, L. E., 1978: The occurrence and distribution of Sirococcus shoot blight of spruce in Kansas. Plant Dis. Reptr. 62: 648-650
Sinclair, W. A.; Lyon, H. H. and Johnson, W. T., 1987: Diseases of trees and shrubs. Cornell University Press. 134-5
Smith, R. S.; McCain, A. H.; Srago, M.; Krohn, r. J. and Perry, D., 1972: Control of Sirococcus tip blight of Jeffrey pine seedlings. Plant Dis. Reptr. 56: 241-242
Soukup, F., 1994: Fungal pathogens of Picea pungens in Czech Republic. Z pravy-lesnickeho-vyzkumu: 39:1. 15-18
Sutherland, JR.; Lock, W. and Farris, S. H., 1980: Sirococcus blight: a seed-borne disease of container-growth spruce seedlings in Coastal British Columbia forest nurseries. Can. J. Bot. 59. 559-562
Sutherland, JR. and West, RJ., 1990: Cone and seed diseases of conifers in Canada. Processing's cone and seed pest workshop. Information report Newfoundland and Labrador region. Forestry Canada. No. N-X-274: 24-36
Tainter, F. H. and Baker, F. A., 1996: Principles of forest pathology. John Wiley & Sons. INC. 640-1
Wall, R. E. and Magasi, L. P., 1976: Environmental factors affecting Sirococcus shoot blight of black spruce. Can. J. For. Res. 6: 448-452
Thanks for your visiting and back to main page
