Arthropods as vectors of esca-related pathogens: Transmission efficiency of ants and earwigs and the potential of earwig feces as inoculum source in vineyards

The spread of Grapevine trunk diseases (GTDs) such as esca concerns wine growers worldwide. Besides rain-splash and air currents, arthropods may play an additional role in the dissemination of esca-related pathogens such as Phaeomoniella chlamydospora (Pch) and Phaeoacremonium minimum (Pmm). The present study confirms that black garden ants (Lasius niger L., Formicidae: Formicinae) and European earwigs (Forficula auricularia L., Dermaptera: Forficulidae) can, under artificial conditions, efficiently transmit spores of Pch and Pmm to healthy grapevine cuttings, causing new infections.
The potential of earwig feces as inoculum source in vineyards is additionally discussed. Spores of Pch and Pmm retained germination ability after earwig gut passage, and infectious feces successfully infected wounded grapevine cuttings under artificial conditions. However, molecular detection frequencies of esca-related pathogens in earwig feces collected from the field were very low. With this, the risk of earwig feces as inoculum source for esca-related pathogens is probably only marginal.
However, arthropods carrying esca-related spores on their exoskeletons, such as ants and earwigs, might contribute to the overall spread of esca in vineyards.
The invasion of GTDs during the phase of pruning wound susceptibility, either by arthropod vectors or by airborne spores, can efficiently be prevented by adequate pruning wound protection.