Influence of an Insecticidal Soap on Several Foliar Diseases of Foliage Plants. A. R. Chase, Assistant Professor of Plant Pathology, University of Florida, IFAS, Agricultural Research Center, Apopka 32703. L. S. Osborne, Assistant Professor of Entomology, University of Florida, IFAS, Agricultural Research Center, Apopka 32703. Plant Dis. 67:1021-1023. Accepted for publication 29 March 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1021.

An insecticidal soap was tested against the following pathogen-suscept combinations: Alternaria panax + Brassaia actinophylla (schefflera), Bipolaris setariae + Chrysalidocarpus lutescens (areca palm), Fusarium moniliforme + Dracaena marginata (red-edge dracaena), and Myrothecium roridum + Dieffenbachia maculata (dieffenbachia). In greenhouse trials, soap applied at the rate recommended for mite control (12.62 mg a.i./L) significantly reduced the severity of Alternaria leaf spot of B. actinophylla and Bipolaris leaf spot of C. lutescens. In contrast, the same rate of soap applied to D. maculata and D. marginata significantly increased fungal leaf spots of these plants. In laboratory trials with all four pathogens, soap incorporated into culture medium at rates as low as 0.63 mg a.i./L significantly reduced colony growth.

Keyword(s): phytotoxicity.