Fusarium wilt and crown rot of sweet basil: Involvement of soilborne and airborne inoculum

Fusarium oxysporum f. sp. basilici causes wilt and crown and root rot in sweet basil (Ocimum basilicum) in all basil-growing regions of Israel. Wilting and death of basil plants were recorted, and isolates of F. oxysporum were obtained at high frequency from roots and all aboveground parts of diseased plants. Inoculation tests with representative isolates verified that the causal agent is F. oxysporum f. sp. basilici. F. oxysporum f. sp. basilici causes both wilt and crown and root rot. The following symptoms were observed: wilt of plants at all stages of growth, brown and black discoloratoin of roots and lower stems, continuous and discontinuous black lesions on stems, blackening and drying of vegetative apices, growth retardation, and xylem discoloration. The stems were frequently covered with a pink-orange layer consisting mainly of macroconidia, which could become airborne, as revealed by propagule trapping. Therefore, the pathogen has characteristics of both soilborne and airborne pathogens. F. oxysporum f. sp. basilici was readily recovered from structure inside the greenhouse, including concrete stumps, string, pipes, and walls. Seeds collected from diseased plants were infested with the pathogen and producted diseased plants bearing infested seeds. Because the pathogen is easily disseminated, a holistic approach is necessary to control it. Because of the variety of symptoms associatd with this disease, we suggest renaming it "Fusarium wilt and crown rot.".