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Orchid Pest Targeted in Hawaii Studies

By Marcia Wood
September 19, 2000

Small snails that feast on roots of exotic Hawaiian orchids are the focus of new studies by Agricultural Research Service scientists in Hilo, Hawaii. The tiny mollusks, known to scientists as Zonitoides arboreus, are hard to detect and even harder to kill with commercial chemicals, according to ARS biologist Robert G. Hollingsworth.

Also called bush or orchid snails, they have bluish-grey bodies protected by yellow-brown, translucent shells. Their coloration, plus their small size (a full-grown adult is smaller than a fingernail), make the snails hard to find. In addition, they live and work independently, so they are harder to see than if they stayed in groups.

In a survey, Hollingsworth and colleague Kelvin T. Sewake of the University of Hawaii found that about half of the growers that they queried in Hawaii complained that Z. arboreus costs them, on average, about $5,000 a year in control expenses and lost sales. Even if only two or three snails are feeding on an orchid in a 4-inch pot, the marauding mollusks can eat up all of the surface roots in only a couple of months.

To combat the pest, Hollingsworth is trying to learn more about its biology. And he's working to build a large colony of wild snails for his tests of molluscicides that can be used to kill the snails without harming the orchids.

An article in the September 2000 issue of ARS’ Agricultural Research magazine tells more.

Horticultural research is a key part of ARS’ mission. For more information on ARS programs that impact horticulture see the list of "Crop Production, Product Value and Safety" national programs at:

ARS is the USDA’s chief research agency.

Scientific contact: Robert G. Hollingsworth, ARS U.S. Pacific Basin Agricultural Research Center, Hilo, Hawaii; phone (808) 959-4349, fax (808) 959-4323,