Biological Noncontrol; November 1997; Scientific American Magazine; by Beardsley; 2 Page(s)

For decades, biologists have been fighting fire with fire by releasing exotic organisms, often insects, to attack pests and weeds that threaten crops and ruin rangeland. New research has shown that a weevil brought to North America to devour an invader called musk thistle is also damaging relatively harmless thistles belonging to a different genus. The finding has prompted investigators to put on hold experimental releases of another exotic insect that they were hoping would join the fight against musk thistle.

Musk thistle arrived in North America in the mid-19th century. The Eurasian weevil Rhinocyllus conicus was first released to combat it in 1968, and releases continue. The insect¿s larvae eat into the thistle¿s flower heads and feed on the seeds there. Paul E. Boldt of the U.S. Department of Agriculture¿s Grassland, Soil and Water Research Laboratory in Temple, Tex., estimates that Rhinocyllus saves farmers hundreds of millions of dollars every year because it allows them to use less herbicide.