Sustainable Control of Spotted Knapweed (Centaurea stoebe)

Abstract

Spotted knapweed is native to Eastern Europe, with a locally scarce but widespread distribution from the Mediterranean to the eastern region of Russia. The plant is one of over a dozen Centaurea species that were accidentally introduced into North America and now is found in over 1 million ha of rangeland in the USA and Canada. Land managers spend millions of dollars annually in an attempt to control spotted knapweed and recover lost forage production, and meanwhile the plant perse- veres as a detriment to native biodiversity and soil stability. These ecological concerns have motivated intense scientific inquiry in an attempt to understand the important fac- tors explaining the unusual dominance of this species. Substantial uncertainty remains about cause–effect relationships of plant dominance, and sustainable methods to control the plant remain largely unidentified or controversial. Here, we attempt to resolve some of the controversies surrounding spotted knapweed’s ability to dominate invaded com- munities, and focus on what we believe is a sustainable approach to the management of this species in grasslands, rangelands, and forests. Application of both cultural and bio- logical control tools, particularly the concurrent use of foliage, seed, and root feeding insects, is believed sufficient to decrease densities of spotted knapweed in most areas to levels where the species is no longer a significant ecological or economic concern