Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/1996
Publication Date: N/A
Technical Abstract: Ornamentals in tropical and subtropical regions have exhibited symptoms similar to bacterial diseases. Symptoms often coincide with the application of benomyl. Benlate DF50 was applied at label drench rates to ferns and orchids maintained under field conditions. Roots of orchids and ferns were subsequently screened for rhizobacterial populations. Bacteria populations were estimated using a standard dilution plating of rhizospher subsamples. Pseudomonads, which are primarily responsible for the observed plant symptoms, were isolated using Sands-Rovira agar. Potentially phytotoxic isolates were identified and evaluated in a lettuce seedling bioassay. Rhizosphere populations from plants were quite variable. However, rhizosphere isolates often reduced seedling growth 50% compared to controls. For example, 40% of the isolates from one set of orchids exhibited a 75% reduction in root length over controls. This indicates that potentially phytotoxic bacteria are present in the rhizosphere and that treatment with benomyl may stimulate these populations.