Endotherapy of infected grapevine cuttings for the control of Phaeomoniella chlamydospora and Phaeoacremonium minimum

The pathogens Phaeomoniella chlamydospora and Phaeoacremonium minimum are associated with different syndromes of the esca disease complex affecting grapevine propagation material, and young and adult plants. Infections by these fungi occur in grapevine nurseries and in vineyards, with disease control strategies providing limited protection in both cases. Several chemicals are effective in vitro against these two pathogens, but treatment of infected plants, especially endotherapy, has not yet proven satisfactory. Five chemicals (elemental silver, fosetyl-Al, glutaraldehyde, hydrogen peroxide and Blad-containing oligomer) were tested in vitro, with the first four also tested in planta, by means of endotherapy, against Pa. chlamydospora and Pm. minimum. All chemicals were effective in vitro for preventing growth of both pathogens, at different concentrations. Endotherapy of rooted grapevine cuttings (cv. Touriga Nacional) was effective against Pa. chlamydospora for all the tested chemicals, with reductions in the frequency of re-isolation of this pathogen of 91-95% (glutaraldehyde), 68-96% (hydrogen peroxide), 68-77% (elemental silver) and 58-59% (fosetyl-Al) when compared with the water-treated experimental controls. The only treatment that was effective against Pm. minimum was glutaraldehyde, providing a 75-83% reduction in re-isolation frequency. These results indicate that endotherapy of young grapevines during early stages of infection may be an effective control strategy, especially against the wood pathogen Pa. chlamydospora.