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A survey of common and uncommon weed species usually showing Verticillium wilt symptoms was carried out during 1992–2000 in Crete, Greece.Verticillium dahliaewas isolated in 48 out of 182 sampled fields, in which several weed species were grown, from several locations in Oropedio, Lasithi. Altogether, 124 isolates ofV. dahliaewere recovered from the vascular stem-tissue of 19 weed species, belonging to ten botanical families. Pathogenicity trials with 13 out of 19 weed species that have never been reported as hosts of the fungus, using for inoculation isolates which originated from the same weed species, resulted in infection of all of them, showing various disease symptoms. Seven weed species (Anthemis melanolepis, Cardaria draba, Convolvulus arvensis, Erodiumsp.,Euphorbia helioscopia, Helminthotheca echioidesandSinapis alba) are new hosts worldwide, and six additional species (Euphorbiasp.,Lactuca serriola, Raphanus raphanistrum, Sinapis arvensis, Sonchus oleraceusandTrifoliumsp.) are new hosts for Greece. The most susceptible (isolation frequency: 27.9–52.8%, moderate disease severity) species were:Capsella bursa-pastoris, C. draba, Chenopodium album, Senecio vulgarisandSolanum nigrum. Less susceptible (isolation frequency: 4.8–17.8%, slight disease severity) were:Amaranthussp.,A. melanolepis, C. arvensis, Erodiumsp.,Euphorbiasp.,E. helioscopia, H. echioides, L. serriola, Malva sylvestris, R. raphanistrum, S. alba, S. arvensis, S. oleraceusandTrifoliumsp. Some species —C. draba, C. album, L. serriolaandS. nigrumL. — that usually showed external and vascular wilt symptoms, occasionally exhibited only reduced growth. Visible symptoms under natural field conditions in all 13 weed species that had never been reported as hosts ofV. dahliaewere similar to those observed after their artificial inoculation. The fungus was not isolated fromFoeniculum vulgaressp.piperitum, Oxalis corniculataandStellaria media, among other species.

To determine the host range ofVerticillium dahliaeamong the cultivated species in Crete, Greece, studies were carried out during 1992–2000. Based on disease symptoms observed on 28 vegetable and forage species grown in a field naturally infected byV. dahliae, and an extensive survey of the most common cultivated species grown under natural conditions, seven hosts belonging to four botanical families not previously reported as susceptible to Verticilliun wilt, and 12 hosts belonging to seven families new for Greece, were recorded. The worldwide new hosts are: anise (Anethum graveolens), chard (Beta vulgarisssp.cicla), chickpea (Cicer arietinum), wild sweet pea (Lathyrus ochrus), lentil (Lens culinaris), marigold (Tagetes erecta) and vetch (Vicia sativa). These species could be infected by their hosts-of-originV. dahliaeisolates during pathogenicity tests.

The severity of Verticillium wilt symptoms increased 20-30 days earlier in the season in tomato plants in the presence of Tobacco Mosaic Virus than in plants infected with fungus alone. There were no differences in symptom intensity between tomato plants infected withFusariumalone and with aFusarium-TMV combination. The increase of fungus infectivity in aVerticillium-TM’V combination treatment is suggested to be a synergistic effect.