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Occurrence of Severe Outbreaks of Leaf Mold Caused by Fulvia fulva in Greenhouse Tomatoes in Chile

Severe outbreaks of leaf mold, affecting as much as 100% of the plants, have occurred in greenhouse tomatoes (Lycopersicon esculentum Mill.) in the V Region in the central zone of Chile (32°50′ to 33°10′ latitude south) during the past 2 years. Symptoms consisted of yellow spherical to elongated leaf spots, first noticeable on the upper surface of older leaves, followed by leaf necrosis and defoliation. Invariably, an olive green-to-gray leaf mold developed on the under surface of the spots. No symptoms were observed on fruits and rarely occurred on petioles and stems. Isolation on acidified potato dextrose agar (APDA) consistently yielded dark green colonies of a very slow growing fungus that was identified as Fulvia fulva (Cooke) Cif. (=Cladosporium fulvum Cooke) (1). Identification was based on the presence of a dark septate mycelium, ovoid to ellipsoid conidia, usually one or two cells, pale or slightly yellow, 11 × 40 μm long, and the presence of mostly unbranched conidiophores that were broader at the tip. Conidia were produced in short chains, and a very distinctive hilum was always observed (1,3). Thin sections of leaf lesions revealed the presence of inter- and intracellular mycelia that protruded through the stomata forming a small stroma in the stomatal cavity from which the conidiophores were produced. Leaf inoculations of tomato cvs. Fortaleza and Cal-Ace with a mixture of mycelia and conidia from isolates Fv1 and Fv2 on APDA (approximately 10⁶ propagules per ml) and with three different samples of conidia (10⁶ conidia per ml) obtained directly from actively growing lesions resulted in the development of pale to dark yellow spots after 12 to 15 days of incubation under greenhouse conditions (temperatures ranging from 9 to 30°C). Leaf spots developed mainly on inoculated leaflets, but occasionally symptoms were obtained on other leaflets on the same leaf. Reisolations made from samples of artificially inoculated leaves always yielded F. fulvia on APDA. Therefore, it was concluded that F. fulvia was the cause of the severe outbreaks of tomato leaf mold found in central Chile. Previously, it has been reported in northern Chile (I Region approximately 2,000 km away) (2). To our knowledge, this is the first confirmed report of leaf mold on greenhouse tomato in central Chile.

References: (1) P. Holliday and J. L. Mulder. Fulvia fulva. No. 487 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1976. (2) F. Mujica and C. Vergara. Flora Fungosa Chilena. 2nd ed. Universidad de Chile, Facultad de Agronomía, Santiago, Chile, 1980. (3) A. F. Sherf and A. A. Macnab. Vegetable Diseases and Their Control, 2nd ed. John Wiley and Sons, New York, 1986.