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Glorious Gardenias Get Boost From ARS Scientists

By Marcia Wood
September 14, 2004

It's been said that the sweet, exotic scent of a single, creamy-white gardenia blossom can perfume an entire room. Perhaps best known as a corsage flower for a prom, wedding or other special occasion, gardenias also make a great gift as a potted plant.

Several years ago, federal and State of Hawaii agencies lifted a 50-year-old ban, thus allowing plant nurseries in Hawaii to ship potted gardenias or cut blooms to the U.S. mainland. Hawaii's nurseries can do that if agricultural inspectors determine that their plants are free of a tiny pest called the coffee green scale.

The change in regulations resulted in part from studies by biologist Robert G. Hollingsworth of the Agricultural Research Service's U.S. Pacific Basin Agricultural Research Center at Hilo, Hawaii, and by Arnold H. Hara, professor of entomology at the University of Hawaii.

Known to scientists as Coccus viridis, the soft-bodied, six-legged coffee green scale feeds on gardenia, citrus and a host of other plants, including its namesake, coffee.

For several years, Hollingsworth monitored coffee green scales in a commercial, 2-acre gardenia plot on Hawaii Island. He was particularly interested in determining whether very young scales, called crawlers, were being blown into the gardenia field by winds coming off the Pacific Ocean. That was a popular, but unproven, notion about how plants were getting infested.

His research showed that windborne crawlers weren't the main problem. Instead, scale infestations resulted from incomplete control using pesticides. Admittedly, adult scales are easy to overlook: They're greenish-yellow ovals, only about one-tenth-inch in size.

Growers already know that careful use of chemicals to control another insect--ants--is key to long-term control of scales. Ants of various species are scales' foremost friends. They ward off scales' natural enemies and carry scales to noninfested plants.

Read more in the September 2004 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.