Mesquite-Eating Insects Get New Australian Home

Two South American insects found by U.S. scientists have been released in Australia to combat mesquite, considered a pest in that country.

In the western U.S., native mesquite plants fix soil nitrogen, grace gardens and provide nectar for honeybees. But too much mesquite on rangeland can mean that other, more nutritious forage plants get crowded out. Mesquite costs the U.S. grazing industry an estimated $250 to $500 million annually.

South America is home to 31 mesquite species, kept largely in check by a variety of natural organisms including insects. Scientists with USDA’s Agricultural Research Service have searched in Argentina, Paraguay and Brazil, looking for natural biocontrols that might be suitable for the U.S. A seed-eating insect, for example, might control mesquite’s spread without harming existing mesquite plants.

The scientists, based at ARS’ South American Biological Control Laboratory in Buenos Aires, Argentina, haven’t yet found potential mesquite biocontrols for the U.S. But they found a few insects that could benefit other nations.

Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) has evaluated two of these insects--the leaf-tier moth (an Evippe species) and a psyllid (Prosopidopsylla flava). Both feed on leaves of mature mesquite plants.

After 15 months of quarantine study in Australia, the leaf-tier moth has been released there. CSIRO scientists had to be sure the insect was safe for wild native plants and farmers’ crops. The psyllid has also proven safe and will be released later.

The cooperation is the latest in a history of shared research. In Brisbane, Australia, ARS maintains a laboratory in cooperation with CSIRO. The lab’s main mission: finding potential biocontrols for the melaleuca tree. This Australian native has become a pest in the Florida Everglades. There, in 1997, ARS scientists test-released Australian weevils that eat the tree’s leaves.

Scientific contact: Hugo A. Cordo, ARS South American Biological Control Laboratory, Buenos Aires, Argentina, phone (541) 662-0999, fax (541) 452-4838, [email protected].