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IPM Saves Roses, Reduces Pesticide Use

May 3, 2007

UC Davis researchers are reporting the largest successful use of integrated pest management in the commercial floriculture industry. They controlled two key pests on cut-rose plants by following a careful program of introducing predators, applying pesticides and revising culture (growing) conditions.

As a result, they reduced pesticide use, which is good for worker health and safety, the environment and the growers' bottom line.

Cut-rose production is the largest component of the $300 million California cut-flower industry. In the most recent data available, from 2001, California produced 66 percent of the U.S. rose crop, with a wholesale value of $45 million.

The pests successfully controlled were twospotted spider mites (Tetranychus urticae) and western flower thrips (Frankliniella occidenalis).

The study -- conducted in close collaboration with eight commercial growers in San Diego, Santa Barbara and Santa Cruz counties -- showed that a predatory mite called Phytoseiulus persimilus could effectively and economically control twospotted spider mites. The growers applied vials of P. persimilus (containing 2,000 predators each) when between 10 percent and 25 percent of randomly sampled rose leaves were infested.

To control western flower thrips, growers limited pesticide spraying to just the upper canopy of the hedge (at 70 gallons per acre) -- where thrips are most prevalent -- rather than the full-volume sprays (at 275 gallons per acre) typical in conventional cut-rose greenhouses. The growers also implemented cultural controls such as removing fully open flowers, where thrips lay their eggs.

Details of the study are published in the April-June issue of California Agriculture, a peer-reviewed journal published by the University of California.

The research program was the result of a state-sponsored partnership among cut-flower growers, scientists and pesticide regulators. Since the 1970s, the University of California has been a global leader in promoting IPM, or integrated pest management, which bases agricultural pest-management decisions on economic thresholds and encourages the strategic use of biological, cultural and chemical controls in order to limit environmental impacts.

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