Occurrence of scab disease of pecan caused by Cladosporium caryigenum in Argentina

Pecan ( Carya illinoinensis ) is a new crop in Argentina. The planted area is expanding quickly with around 4000 h in the Pampas region, an area characterized by around 1000 mm annual rainfall and high humidity. In 2007 and 2008 typical scab symptoms on seedlings and mature trees were commonly observed in La Plata: small, circular black leaf spots, often coalescing, and an olive-green to black mould below. Nuts, twigs and petioles also had black spots. A Cladosporium- like fungus was isolated on potato dextrose agar (PDA) from surface-sterilized pecan leaves collected from the Experimental Station of UNLP, La Plata. The conidiophores were dark brown, erect and septate (50‐188 × 4‐5 μ m). Conidia were in chains, irregular, ovoid to ellipsoid, a few with two cells, pale olive green, (4‐8 × 6‐22 μ m). These characteristics agree with a published description of Cladosporium caryigenum (Gottwald, 1982). Detached leaves from one year-old seedlings, obtained from a tree selected as a source of rootstock were inoculated with the C. caryigenum isolate using a modified method described by Conner (2002). Conidia were harvested from two week-old PDA cultures grown at 24 ° C and a suspension in sterile distilled water adjusted to 1 × 10 6 conidia mL − 1 . The