THE ECOLOGY OF VERTICILLIUM DAHLIAE IN FRAXINUS AND ACER SPECIES (WILT PATHOGEN, EGGPLANT, MULCH).

다국어 초록 (Multilingual Abstract)

Vegetative compatibility group (VCG) analysis was used to separate strains of <italic>Verticillium dahliae</italic>. Forty-five woody plant isolates, primarily from north central USA, were predominately VCG 1 and 3. Several isolates were found in VCG 2 and 4 which predominate on vegetable crops. All five tree isolates from Oregon were VCG 4B which was not found among any other tree isolates in this study. This indicates that movement of infected nursery stock from different geographic locations could result in the introduction of new VCGs into an area.
When chips were piled before use, temperatures high enough to kill pathogens were measured, but there was considerable fluctuation in the temperature throughout the pile. When eggplant was used as an indicator for the presence of <italic> V. dahliae</italic> in wood chips, the highest number of the plants became infected when the chips were freshly chipped. However, <italic>V. dahliae </italic> was recovered from some eggplants mulched with chips that had been in the pile for 3, 7 and 20 days. Amur maple and green ash seedlings mulched with the same wood chips used to mulch eggplants did not result in infection of the tree seedlings after 2 growing seasons.
Examination of material from trees suspected of being infected with the wilt pathogen showed that observation of symptoms must be followed up with laboratory analysis to separate Verticillium wilt from other diseases and disorders. Symptoms on green ash include mottling, veinal chlorosis, marginal scorch and defoliation.
The prevalence of Verticillium wilt in the North Central region can be confirmed by laboratory analysis following observation of symptoms, and the fungus can be identified to a specific VCG to ascertain threats to local urban forests. However, <italic>V. dahliae</italic> infested wood chips are a potential threat to healthy trees when used as a mulch. Piling infected wood chips for several weeks before use will reduce the number of viable propagules of <italic> V. dahliae</italic>. Leaves from infected trees should be collected and composted prior to use in landscapes and as a sanitation procedure in nurseries since foliage from Verticillium wilt infected green ash transmitted the disease to eggplant.