First Report of Thielaviopsis Trunk Rot of Date Palm in Italy

As an alternative to Canary Island date palm (Phoenix canariensis Chabaud), date palm (P. dactylifera L.) is being planted in Sicilian landscapes. In January 2006, severe symptoms of trunk rot were noticed on 10 7- to 8-m high mature date palms in the central square of Aci Bonaccorsi (Catania) in eastern Sicily. In June 2004, these palms were transplanted directly from Egypt. In 4 of 13 planted date palms, the canopy suddenly fell off the trunk. The canopy of all palms appeared normal and healthy with no stem bleeding observed before trunk collapse. Cross sections of affected date palms revealed a brown rot of nonlignified or lightly lignified tissues along with a strong odor of fermented fruit (amyl acetate) associated with the presence of Geotrichum candidum Link ex Pers. Brown rot was not detected in three of the date palms examined. Symptoms were not detected on lignified and external fibers. Internal tissue adjacent to the rotted areas was placed on carrot agar amended with 500 μl of streptomycin sulfate and acidified (lactic acid; pH = 3.6) potato dextrose agar. Large sections (10 to 18 cm) of affected palm tissues were maintained in a moist chamber for 8 days. Microscopic examinations of five single-conidia isolates on media and sporulation from affected tissues yielded Thielaviopsis paradoxa De Seyn. (Höhn) (1). Endoconidia measuring 3 to 5.5 × 7 to 11 μm were cylindrical to somewhat oval when mature, hyaline to mid brown and smooth walled. Endoconiodophores were usually straight, colorless to pale brown, as much as 150 μm long, with a terminal spore-bearing cell through which spores are born. Chlamydospores were smooth, thick walled, brown, in chains, and were 7.5 to 13 μm width × 10 to 18 μm length (values referred to 50 examined chlamydospores). T. paradoxa is a pathogen that can infect any part of a palm and its pathogenicity to date palm is well documented (3). T. paradoxa is endemic in northern Italy (Ligurian Riviera) on P. canariensis where it causes a disease known as bud rot (2). To our knowledge, this is the first record of trunk rot caused by T. paradoxa on date palm in Italy and is the first report of the fungus in Sicily. It is recommended to avoid the foreign trade of mature date palms from known infected areas because of the symptomless infections by this pathogen. References: (1) A. R. Chase and T. K. Broschat, eds. Diseases and Disorders of Ornamental Palms. The American Phytopathological Society, St. Paul, MN, 1991. (2) A. Garibaldi et al., eds. Malattie Delle Piante Ornamentali. Calderini Edagricole, Bologna, Italy, 2000. (3) P. Suleman et al. Plant Dis. 85:80, 2001.