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To Guard Mums, Spice the Fungi

By Jill Lee
December 31, 1997

Cut chrysanthemums are a traditional winter bouquet. But florists and nurserymen must guard these fragrant flowers against fusarium wilt, and the primary means of protection--fumigation with methyl bromide--will be banned in the year 2001 under guidelines of the Clean Air Act. Spices such as hot peppers may provide an alternative.

Researchers with the U.S. National Arboretum's Floral and Nursery Plants Research Unit have found that extracts made from hot peppers and cloves send the pathogen packing. The arboretum is part of USDA's Agricultural Research Service.

The Society of American Florists estimates that 57 million chrysanthemum blooms and 100 million pompons--the smaller flowers used in bouquets--were sold in 1995. Making sure these flowers are healthy protects an important market.

In laboratory studies, ARS scientists treated soils with extracts of clove and cassia tree. They also tested a mixture of chili pepper extract and essential oil of mustard.

The chili pepper mixture knocked out 99.9 percent of the fusarium populations. Although clove and cassia killed less fungus--97.5 percent and 96.1 percent, respectively--they maintained their fungus-suppressing power longer than the pepper.

The scientists hope to devise a two-step strategy: first adding the spices to the soil to kill fusarium, then introducing friendly microorganisms to crowd out any fusarium that survive the spicy onslaught.