Since 2019 severe damages on mature deciduous oak trees were detected in a forest stand in the Euganean hills (Veneto, Italy). In particular, several declining oak trees were found to be attacked by the European shot-hole borer Anisandrus dispar F. (Coleoptera; Curculionidae, Scolytidae). In addition to the direct damage caused by the insect, infested branches showed sunken bark cankers with deep necrotic lesions and reddish brown to dark brown exudations around the entry holes, giving them a “bleeding” appearance. Internally, tissues surrounding the branch galleries were characterized by typical dark brown fungal lesions of varying width extending through the inner bark to the woody tissues. Although A. dispar has been found in Europe on several woody hosts, several aspects of its ecology are still unknown. In particular, no information is available on the ecological interactions existing between this ambrosia beetle species and the main fungal pathogens involved in the aetiology of oak decline. Therefore, a study was conducted in an infested oak stand in spring-summer 2022 to isolate and characterize the fungal community present in the necrotic wood tissues surrounding the beetle galleries and associated to dispersing A. dispar females which were collected with ethanol-baited traps. Isolations carried out from 490 A. dispar adult females and 67 symptomatic branch samples yielded mainly fungal taxa known to be canker and branch dieback agents on oaks. Botryosphaeriaceae, Cryphonectriaceae, Graphostromataceae and Nectriaceae were the most abundant taxonomic groups. In particular, the species Botryosphaeria dothidea, Dothiorella iberica, Neofusicoccum mediterraneum and Neofusicoccum parvum were isolated from both Anisandrus dispar and oak tissues. Our findings provide new insights into the multitrophic interactions of A. dispar in Italy and its role as a potential vector of oak pathogens.
A partire dal 2019 sono stati osservati danni gravi causati dallo scolitide Anisandrus dispar su querce deperenti situata in una delle principali aree boschive dei Colli Euganei in Veneto. In prossimità del foro scavato dell’insetto, su rami e branche erano presenti vistosi cancri caratterizzati da profonde fessurazioni della corteccia e lesioni necrotiche spesso umide per la presenza di essudati di colore marrone/rossastro tendente al nero col passare del tempo. Internamente, i tessuti legnosi, adiacenti alle gallerie scavate dall’insetto, apparivano necrotici per lunghi tratti. Sebbene la specie A. dispar sia ampiamente riportata in Europa su diverse specie arboree, molti aspetti legati alla bioecologia di questo insetto rimangono ancora sconosciuti. In particolare, sono ancora limitate le informazioni riguardanti le interazioni ecologiche tra questo insetto e i principali patogeni fungini coinvolti nell’eziologia del deperimento delle querce Pertanto, vista la preoccupante espansione degli attacchi di A. dispar nei boschi di querce del Veneto e l’assenza di informazioni sui patogeni fungini associati all’insetto, nell’ambito di questa tesi si è ritenuto opportuno andare a studiare le comunità fungine associate ai tessuti legnosi necrotici lungo le gallerie scavate dall’insetto e presenti sull’esoscheletro delle femmine catturate con trappole innescate con etanolo. Gli isolamenti effettuati su 490 femmine adulte e 67 campioni di rami sintomatici hanno consentito di ottenere in coltura pura numerosi microrganismi fitopatogeni agenti di cancri e disseccamenti su querce. In particolare, le specie Botryosphaeria dothidea, Dothiorella iberica, Neofusicoccum mediterraneum e Neofusicoccum parvum (fam. Botryosphaeriaceae) sono state isolate con una frequenza elevata sia dagli adulti di A. dispar sia dai tessuti legnosi sintomatici. Nel complesso, le ricerche effettuate hanno permesso di ampliare le conoscenze scientifiche sulle interazioni multitrofiche tra A. dispar, funghi fitopatogeni e querce in Italia e sul suo ruolo dell’insetto come vettore di varie specie appartenenti alla famiglia delle Botryosphaeriaceae.
Patogeni fungini associati alle gallerie del coleottero scolitide Anisandrus dispar in querce deperenti
VIGOLO, SARA
2022/2023
Abstract
Since 2019 severe damages on mature deciduous oak trees were detected in a forest stand in the Euganean hills (Veneto, Italy). In particular, several declining oak trees were found to be attacked by the European shot-hole borer Anisandrus dispar F. (Coleoptera; Curculionidae, Scolytidae). In addition to the direct damage caused by the insect, infested branches showed sunken bark cankers with deep necrotic lesions and reddish brown to dark brown exudations around the entry holes, giving them a “bleeding” appearance. Internally, tissues surrounding the branch galleries were characterized by typical dark brown fungal lesions of varying width extending through the inner bark to the woody tissues. Although A. dispar has been found in Europe on several woody hosts, several aspects of its ecology are still unknown. In particular, no information is available on the ecological interactions existing between this ambrosia beetle species and the main fungal pathogens involved in the aetiology of oak decline. Therefore, a study was conducted in an infested oak stand in spring-summer 2022 to isolate and characterize the fungal community present in the necrotic wood tissues surrounding the beetle galleries and associated to dispersing A. dispar females which were collected with ethanol-baited traps. Isolations carried out from 490 A. dispar adult females and 67 symptomatic branch samples yielded mainly fungal taxa known to be canker and branch dieback agents on oaks. Botryosphaeriaceae, Cryphonectriaceae, Graphostromataceae and Nectriaceae were the most abundant taxonomic groups. In particular, the species Botryosphaeria dothidea, Dothiorella iberica, Neofusicoccum mediterraneum and Neofusicoccum parvum were isolated from both Anisandrus dispar and oak tissues. Our findings provide new insights into the multitrophic interactions of A. dispar in Italy and its role as a potential vector of oak pathogens.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/49071