21. Areas with large amounts of shade or high levels of water discourage diffuse knapweed growth. 22. Various colour-forms of greater knapweed may be found as well as common twayblade. 23. The parasitic knapweed broomrape ( " Orobanche elatior " ) is regularly recorded. 24. Nevertheless, knapweed control is better when the moth works in tandem with other insects. 25. As a result, diffuse knapweed is able to establish more predominantly in this new area. 26. It lives on spotted and diffuse knapweed and has not been found to damage other plants. 27. It was first released as a knapweed biocontrol in the United States in 1991 from Greece. 28. In drier grassland areas, there is common knapweed , agrimony and ox-eye daisy. 29. A native to Eurasia, Russian knapweed was introduced into North America in the late 19th century. 30. Greater knapweed is found growing in dry grasslands, hedgerows and cliffs on lime-rich soil.
