Occurrence of Foliicolous Parasitic Alga Cephaleuros Virescens on Cultivated Ornamental Plants in Southern India

Abstract The algal leaf spot, caused by Cephaleuros virescens Kunze, has been reported in a wide range of plant species from the tropical and subtropical areas worldwide. Investigations on the presence of algal infection mostly involved wild plants and plantation crops of economic interest. Nevertheless, limited studies have examined cultivated ornamental plants for the presence of C. virescens. During the summer and monsoon seasons of 2011 we examined ten leaves of five plants belonging to 86 ornamental plant taxa in 38 families growing in home gardens in Coimbatore, Tamil Nadu, India for the algal presence. Nine of the 86 plant taxa were found to host the algae C. virescens. Although majority of the investigated species are considered as typical hosts of C. vi-rescens, its infection was found only in nine plant species. Although the incidence of the algal leaf spot disease was in general low, there was significant variation in the frequency of occurrence of the algal lesions and the lesion size among the investigated plant taxa and seasons. On plants of five species (Alpinia purpurata, Ficus benjamina, Ficus elastica “Variegata”, Michelia champaca, Polyalthia longifolia), C. virescens was found during both seasons, while infections on the remaining four species (Aglaonema commutatum, Dieffenbachia maculata, Eucalyptus globulus, Syngonium podophyllum) were observed only during the monsoon. The susceptibility of different plant species in a genus and varieties of a species varied suggesting the host influence on the development of infections in addition to variation attributed to the local environmental conditions.