Fusarium wilt of Phoenix canariensis: first report in Greece

Canary Island palm (Phoenix canariensis) is used extensively as a landscape ornamental in Greece. In spring of 2002 a severe disease was observed on these palms in Athens County. First symptoms began on the mature pinnae at the base of the plant, which became dry. Initially the leaflets on one side of the rachis died (Fig. 1), but eventually the entire plant died. When the rachis was sectioned longitudinally, the vascular and adjacent tissue showed linear streaks of brown discoloration (Fig. 2). The disease spread rapidly to neighboring trees. When diseased trees were replaced with new healthy ones, these also became infected.

Fusarium oxysporum was isolated from the discolored vascular tissue of the leaves. Pathogenicity tests were performed using a method modified from Tused et al. (2002), using 9 months old Phoenix canariensis plants and seedlings of Phoenix dactylifera at the three leaf stage. The roots were submerged for 24 hours in a conidial suspension adjusted to 10⁷ conidia per ml, while the control plants were soaked in sterile water. After 43 days the roots of Phoenix canariensis were heavily infected to the extent that only the epidermis and the central axis of the root remained. Subsequently the leaves dried and most of the inoculated Phoenix canariensis plants died. Similarly, disease symptoms were observed on the roots and aerial parts of Phoenix dactylifera palms five months after inoculation. Control plants of both palm species remained healthy. The fungus was reisolated from the diseased plants of both species. Mercier & Louvet (1973) reported Fusarium wilt of Phoenix canariensis caused by Fusarium oxysporum f. sp. canariensis, that also infected Phoenix dactylifera. The disease was reported in many major plant-growing regions worldwide (Plyler et al, 1999). This is the first report of Fusarium wilt of Phoenix canariensis in Greece.