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Biological Control of Leafy Spurge

Establishing Exotic Insects


The five natural enemies of leafy spurge now being released in North America were examined in test plots in Europe and evaluated in quarantine stations in the United States by ARS scientists. They made sure that insects intended for export were healthy, so that they could spread in North America free of diseases and parasites.

Furthermore, the scientists made sure that the new insects would be safe for release in the United States. Stringent import rules prevent introducing foreign organisms that can damage desirable plants.

The ARS scientists checked whether the insects would attack crop and pasture plants, including corn and alfalfa. They also studied the insects' behavior toward North American wild plants that are closely related to leafy spurge. Leafy spurge has seven relatives so rare that they are listed as endangered or threatened, or are under consideration for that status. Tests showed that the five natural enemies of spurge are highly selective in their diet and don't attack commercially grown plants or desirable wild spurge relatives.

After having carefully screened the five leafy spurge enemies, biological control specialists in the Animal and Plant Health Inspection Service faced the challenge of securing a large enough supply of each species to release on the range. The specialists developed ways to mass rear some of them in the laboratory. Other insects proved better suited to having their numbers multiplied in the field.

Field rearing is done in field insectaries, which are small plots of land, generally about 10 acres, infested with leafy spurge. There, the insects are released and protected, so that they can grow and multiply with minimum stress.

State cooperators collect offspring of the released insects to place in satellite insectaries in other locations around the State. The insects also disperse naturally.


JPEG - Using field cages to establish insects
Leafy spurge enemies often are placed in protective field cages to help them become established.
 
JPEG - Shipping carton of flea beetles
Flea beetles can be mass reared and sent to the field in shipping cartons.


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