Occurrence of Cercospora insulana on statice (Limonium sinuatum) in Italy

Abstract

For the past 3 years, fields of statice (Limonium sinuatum) near Pompei, southern Italy have been affected by a previously unrecorded leaf spot disease, which was also found in 2002 near Pescia in central Italy. Infections first occurred in June and spread during the summer. Leaf spots were circular, brown with a darker edge, 3–6 mm in diameter, and surrounded by an orange or reddish halo. Lesions were also observed on the wings of the flower scapes, while scapes proper were not involved. Old lesions enlarged and merged, causing early yellowing and senescence of leaves; heavy infections resulted in severe defoliation and retarded growth or death of panicles. Microscopic inspection of lesions revealed the presence of dark brown stromata with pale brown conidiophores. Conidiophores were septate, unbranched, sinuous, bent at spore scars, averaging 59 µm long × 4·8 µm wide. They bore multiseptate hyaline conidia (95 µm long × 3·3 µm wide on average) which were slightly curved, with truncate bases and subacute tips. These features conform to the reported description of Cercospora insulana, a species recorded on Limonium and other members of the Plumbaginaceae (Chupp, 1953). The species C. insulana was originally described by Saccardo (1915) on L. sinuatum in Malta. Since then the pathogen has been reported from Russia, the USA, Canada, Guatemala, South Africa (Chupp, 1953), Taiwan, Argentina, Israel, Thailand, Myanmar and a number of African countries (J. C. David, CABI Bioscience, Egham, UK, personal communication). Cercospora leaf spot of statice was reported by Pesante (1956) in northern Italy, but the author claimed it had longer conidia (120–180 µm) and described it as Cercospora statices. This difference is questionable because the author measured conidia developing in a moist chamber. Longer conidia were also observed by Jackson (1961). However, as no further outbreaks of the disease have been reported since, and it is no longer possible to make a comparison with the specimens collected by Pesante, to our knowledge this is the first documented report of C. insulana in Italy. The authors thank Dr John C. David (CABI Bioscience, Egham, UK) for confirming the identity of the pathogen as C. insulana.