Then we tested the insects at our European facilities to make sure they wouldn't feed on desirable plants in the United States. Since then, with approval from USDA's Animal and Plant Health Inspection Service, six of the insects have been imported, and five have become established. After ARS scientists release the insects, collaborators like McCaffrey monitor and redistribute them to new sites. Now we use the site as a nursery to collect weevils for use in other weed-infested areas. Sites that show dramatic weed reduction are gratifying, but biological control success is usually hard to measure.
Adults eat developing buds.
Females lay eggs in older buds that remain, and the larvae that hatch eat most of the seeds before they mature. But in some areas where plant numbers are reduced, individual plants grow larger to produce more seed. To better understand the weed, Balciunas plans to compare its seed production in the United States with that in Turkey, where yellow starthistle is native. The weed doesn't persist in its homeland like it does here. If we can discover why that happens, it will give us clues for controlling the weed.