Corticolous mites (Acari) as potential vectors ofCryphonectria parasitica(Murr.) barr hypovirulent strains

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Abstract
Specimens of four species of corticolous mites, Liebstadia humerata Sell. (Oribatida: Protobatidae), Scheloribates latipes (C. L. Koch) (Oribatida: Scheloribatidae), Thyreophagus corticalis (Mich.) (Acaridida: Acaridae), and Zygoribatula laubieri meridionalis Travé (Oribatida: Oribatulidae), were found in cankers, caused by Cryphonectria parasitica on chestnut trees, and were reared on laboratory cultures of the parasite. Monoxenic cultures were carried out using a hypovirulent (H) strain of the blight fungus. A group of mites was transferred from the H cultures to a met auxotrophic virulent (V) strain. Fecal pellets collected aseptically were used to inoculate agar plates. New C. parasitica cultures developed and white colonies with the morphological characters of the hypovirulent strain were obtained. Development of C. parasitica from mites indicated that the mycelial fragments were viable. The dsRNA presence in these cultures obtained from fecal pellets deposited by mites feeding from the blight agent mycelia was emphasized. Inoculation tests in the field confirmed that the white strains developed from the mite's fecal pellets were hypovirulent and suggested that these arthropods play a leading role in the natural spreading of hypovirulence in the chestnut stands.