2014-09-17_REVISION - M2000014 - Laserfiche WebLink

Home Browse Search

Canada thistle: a perennial weed with extensive root system that spreads primarily by root. This is a very persistent weed due to the extensive roots and requires diligent and consistent management to be successful. • Cultural: Maintaining healthy, vigorous stands of desirable species to outcompete the Canada thistle. • Mechanical: Mowing or hand-pulling is not recommended due to the ability of the plant to send more runners and roots to create new plants when cut. If pulling,you must get ALL of the root and root system to prevent further resprouting. • Biological: According to the CDA insectary,insects have not proven effective. But goats and cows have been used to reduce and sometimes eliminate populations. This takes intensive management and control of the animals to be successful. • Chemical: Grand County DNR recommends the use of Milestone Specialty herbicide at a rate of 5 to 7 oz per acre applied from Mid July to October, after all plants have emerged for the season. Common Mullein: A biennial forb that is common along roadsides and disturbed areas. Reproduces by seed only. It is present in fair amount throughout the County and the DNR treats populations to prevent further spread. Management methods include: Cultural: Prevention by minimizing soil disturbance and early detection. Mechanical: Hand pulling or digging is an effective method of control if done prior to seed set. Biological: a curculionid weevil, Gymnaetron tetrum, has been released in the US for Mullein control. Currently it is not available from the CO insectary. Chemical: Grand County DNR recommends using Milestone Specialty at a rate of 7 oz per acre at rosette stage. If plant is bolting, adding 2,4-D at the rate recommended on the label. Other species to be aware of because they are present nearby are the following: Diffuse knapMeed: Biennial or short-lived perennial reproduces by seed. Flowers are usually white, with spiny bracts. Diffuse knapweed has a sporadic presence in Grand County, but the nature of gravel pits with trucks coming from and going to all areas can transport weed seed readily. Management methods include: • Cultural: Prevention by maintaining healthy stands of desirable vegetation and reseeding of disturbed areas. • Mechanical: Hand pulling is effective in small infestations, being sure to get all of the root to prevent resprouting. • Biological: The seedhead weevil(Larinus minutus)and the root weevil fly (Cvnhocleonus achates)provide fair to good control when used in combination with each other. Expect to wait at least 3 to 5 years for the insects to establish and achieve optimum results. This is an option for large infestations. To obtain the insects, contact the Colorado Department of Agriculture, 970-464-7916.