First Report of Leaf Blight on Sweet Persimmon Tree by Pestalotiopsis theae in Spain.

Abstract

During July 1998, a leaf blight caused by Pestalotiopsis theae (Saw.) Stey. was observed at an incidence of 18 to 20% in sweet persimmon (Diospyros kaki L.fil.) orchards in Huelva Province (southwestern Spain). Symptoms appeared on leaves as large grayish brown circular ringspots. Usually, they were solitary, but occasionally, two to three spots occurred on an affected leaf. In severe cases, lesions developed on more than one-third of the leaf, resulting in defoliation. Small black acervular conidiomata were visible in the surface of spots. These conidiomata produced fusiform conidia that were straight or rarely curved, four five-celled euseptate, including three olivaceous or dark brown median cells, and hyaline apical and basal cells with appendages that were slightly constricted at septa. Conidiomata were up to 240 μm in diameter; conidiogenous cells were 6 to 13 × 1.2 to 2.8 μm; conidia were 24.7 × 7.8 μm; three median cells were 16.7 μm long; two to three apical appendages (rarely four) were 28.3 μm long; and straight basal appendage was 5.7 μm. P. theae was consistently isolated on potato dextrose agar from diseased leaves and conidiomata. To confirm pathogenicity, both mycelial plugs and a conidial suspension (1.5 × 106 conidia per ml) of the fungus were used as inocula. Young completely developed leaves from persimmon tree cvs. Sharon and Hanafuyu were inoculated in the laboratory and maintained in a moist chamber for 5 days. Lesions resembling symptoms that occurred in the field were observed on leaves after 5 days. Symptoms were not observed on control leaves inoculated with agar media or sprayed with water. The fungus reisolated from diseased leaves was identical to the original isolates. Based on the morphological characteristics of conidiomata and conidia as well as pathogenicity, the fungus was identified as P. theae (1). This is the first report of this fungus as a pathogen of D. kaki in Europe. Possibly the introduction of P. theae to Spain has been through young imported persimmon plants. Unusual climatic conditions (heavy rainfalls during 1997 in southwestern Spain) have been favorable for disease development. The hot and dry conditions that usually occur during flowering, growing, and maturation of persimmon fruits normally prevent dissemination of inoculum and infection of leaves. For these reasons, the wet areas of southwestern Spain could be more favorable for "grey blight" of persimmon trees. Reference: (1) T.-H. Chang et al. Korean J. Plant Pathol. 12:377, 1996.