ISHS Acta Horticulturae 494: II International Symposium on Chestnut
PRELIMINARY REPORT ON THE OCCURRENCE OF CRYPHONECTRIA PARASITICA (MURRILL) BARR ON DIFFERENT TREE SPECIES IN FRIULI VENEZIA-GIULIA (ITALY) |
| Authors: | G. Frigimelica, M. Faccoli |
| Keywords: | Scolytidae, Cryphonectria parasitica, Castanea sativa, Quercus spp. |
| Abstract:
Within the frame of the forest phytopathological inventory of the Friuli Venezia-Giulia district, several groups of oaks (Quercus spp.) infected with the chestnut blight fungus (Cryphonectria parasitica (Murr.) Barr) were observed. Most of the oaks were found in old chestnut orchards. Because C. parasitica can infect several tree species, the hypothesis was tested that insects boring both in chestnut and oaks may act as possible vectors of fungal spores. Several oak trees infected with C. parasitica and attacked by xylophagous insects were cut down and put into insect emergence boxes. Emerged insects were then washed and the spore load was evaluated. Scolytus intricatus (Ratz.) and Xyleborus monographus (F.) were the only bark beetle species to emerge, and both are able to attack chestnut. All insects were contaminated with several fungi. Scolytus intricatus might be an efficient vector, because its life cycle includes a maturation feeding in the crown of healthy oaks, whereas this is not observed for Xyleborus monographus. Spore suspension was also diluted and distributed on agar medium. Growing colonies of C. parasitica were counted and isolated. In addition, numerous bark samples were collected from both logs and edges of cankers on oak and chestnut. The pathogenicity of these isolates of C. parasitica was evaluated by artificial inoculation on live excised shoots of chestnut, oak and hornbeam. All isolates from oak were classified as virulent. The inoculation trials showed lesions on chestnut and oak 4 weeks after the inoculation, but not on hornbeam. In the district of Friuli-Venezia Giulia it seems likely that bark beetles may act as vectors of fungi, including C. parasitica. The association may provide useful epidemiologic data on the possible spreading of new strains of the fungus from oaks to chestnuts and on the understanding of oak decline. | |
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