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New Beneficial Insects on the Way for Leafy Spurge Control

A French midge and an Italian beetle may soon join the ranks of the biological control agents used in the United States to manage the noxious weed leafy spurge (Euphorbia esula).

Agricultural Research Servicescientists and cooperators in Montana and Europe collaborated to identify, test and import the two insects. Leafy spurge covers at least 5 million acres in 35 states and Canadian provinces.

The midge, Spurgia capitigena, lays eggs near the tip of leafy spurge stems. The developing larvae cause the plant to form a swelling, or gall, and turn up its leaves. The gall, which provides food for the midge larvae, reduces the weed’s ability to produce seeds.

ARS has received permits to release the midge and expects to receive a shipment of insects from France in May. Researchers at the ARS Northern Plains Agricultural Research Center in Sidney, Mont., hope to release the insects early this summer.

A stem-boring beetle, Thamnurgus euphorbiae, is next in line on the spurge control team. ARS researchers at the European Biological Control Laboratory, Montpellier, France, and cooperators showed that the beetle tunnels into spurge stems to lay eggs. The larvae that hatch feed into the stems, weakening the plant and reducing seed production.

The beetle has gained support from the Technical Advisory Group for Biological Control Agents of Weeds, an independent committee that counsels the USDA’s Animal and Plant Health Inspection Service on whether to approve release of a pest-control agent. If APHIS grants a permit, the beetle could be released in 2001.

Both insects have been tested for efficacy against spurge and to ensure they will not harm other vegetation.

These insects would join 12 other beneficial insects imported for leafy spurge control. Unlike existing agents, the new midge and beetle are expected to thrive in sandy, shady or moist soils. That should give land managers new options for spurge management along streams and rivers.

An article about ARS’ program for importing beneficial insects to control leafy spurge and other invasive weeds appears in the March issue of the agency’s monthly magazine, Agricultural Research.

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

Scientific contact: Neal Spencer, Northern Plains Agricultural Research Center, Sidney, Mont., phone (406) 482-2020, fax (406) 482-5038, [email protected]; Paul C. Quimby, European Biological Control Laboratory, Montpellier, France, phone (334) 9962- 3000, fax (334) 9962-3049, [email protected].