Researchers Help Growers Fight Floral Pests

Garden roses--the kind that you buy as “bare-root” plants at the nursery for your home garden--can’t flourish if they’re harassed by soil-dwelling pests called nematodes. That’s why U.S. growers of bare-root roses typically fumigate their fields with methyl bromide, a chemical that kills nematodes and other pests, as well as weed seeds.

Because of indications that methyl bromide depletes the Earth’s protective ozone layer, methyl bromide is now being phased out. Agricultural Research Service scientists in Fresno, Calif., are helping garden-rose growers by testing other compounds that might protect roses.

Plant pathologists Sally M. Schneider and James S. Gerik of the ARS Water Management Research Laboratory in Fresno, Calif., are scrutinizing about a half dozen different compounds, such as propargyl bromide, or combinations of compounds, such as iodomethane plus chloropicirin.

They are also experimenting with different ways of applying the chemicals, such as injecting them into the soil or distributing them through drip-irrigation systems.

The researchers are using concrete pipes, turned on end and buried in the ground, to form small, self-contained study sites called “microplots” for the research. Each pipe is 4 feet long and 18 inches in diameter. Their key target is root-knot nematodes that feed on roots and cause galls to form. Galls interfere with the roots’ ability to take up water and nutrients from soil.

The scientists are collaborating with Jackson & Perkins, the world’s largest grower of roses.

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

The garden roses research is part of an ARS National Program on Methyl Bromide Alternatives.