Leucoptera spartifoliella, an Introduced Enemy of Scotch Broom in the Western United States1

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Abstract
The first attempt to control Scotch broom, Cytisus scoparius Link, by the use of insects was made in 1960, with the introduction of a stem and twig borer, Leucoptera spartifoliella Hübner, from Europe. Additional introductions were made in 1961. Establishment occurred in all 6 release sites. An additional release was made in 1962. Accidentally introduced populations of unknown age and origin also occur at Tacoma, Washington, in extreme northwestern California, and at 2 locations in the San Francisco Bay Area. At Tacoma, Wash., and Crescent City, Calif., L. spartifoliella is attacked by its native European parasite, Tetrastichus evonymellae (Bouché). L. spartifoliella has one generation annually and overwinters in the larval stage in mines on the twigs and succulent stems of Scotch broom. Pupation begins in late March and egg laying is completed by late July. Larvae are nearly half grown by late October. Larval activity causes the twigs to be weakened or to die. Heavily attacked shrubs become covered with dead wood and produce about half the amount of seeds of unattacked plants.

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