Determining the efficacy of Larinus minutus (Coleoptera:Curculionidae) in reducing spotted knapweed populations in Arkansas.

Spotted knapweed (Centaurea stoebe spp. micranthos (Gugler) Hayek) is an exotic, invasive weed that has caused millions of dollars in damage in the northwestern United States and can reduce forage production by more than 88%. Although a successful biological control program for this weed exists in the northwest, the weed is expanding rapidly throughout the southeastern United States, where no comprehensive control program exists. The insect thought largely responsible for the decline in the northwest is Larinus minutus. L. minutus adults were collected from areas around Colorado Springs, Colorado from 2007 through 2011 and were released in Arkansas. Studies to determine the effect of L. minutus on seed and plant densities were conducted in 2010 and 2011. No differences were seen between L. minutus release and non-release sites. On average, 700 L. minutus were released at each of the release sites. Differences in spotted knapweed plant and seed densities are more likely to be seen after populations of L. minutus have had more time to increase.