|BERGFIELD, W A|
Submitted to: The 1890 Association of Research Directors Biennial Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 11/24/1997
Publication Date: N/A
Technical Abstract: Horticultural and agronomic crops receive widespread applications of fungicides for high quality and economical production. Applications of fungicides may control the target pest but there may be non-target effects. When foliar and drench applications are made repeatedly, much of the pesticide contacts soil bacteria. Consequences include increase or decrease ein soil bacterial populations, pesticide degradation by soil bacteria, or pesticide-selected bacteria may affect growth and development of the desirable plants. Abnormal responses of horticultural crops receiving high rates of fungicides resemble bacterial diseases. Appearance of non-target effects may explain some of these problems. Soil and root samples from production sites were screened for fungicide effects on rhizosphere bacteria. Soils with histories of repeated benomyl applications exhibited significant increases in pseudomonad numbers compared with non-history soils. Selected bacterial isolates were highly phytotoxic as demonstrated in lettuce seedling bioassays. Typically, more than half of the isolates from history soils were phytotoxic. Results indicate the need to fully evaluate non-target effects of a pesticide as well as target effects.