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Noxious Weed Management Strategies

A major component of the Undesirable Plant Management Plan is the requirement to provide Douglas County Property Owners with technical assistance in determining methods to control or eliminate their weed problems.  Staff continues to insure County-owned properties are under treatment for weeds, as well as working with other public entities to assist them in their weed control problems.

Prevention, eradication, and control are three general weed management strategies.   Be a good neighbor and control your noxious weeds.

Prevention is the first line of defense to keep weeds from growing in an area. Planting high quality, weed-free crops or grass seed is the basis for good land management. Plant competition is an effective way to prevent the invasion of noxious weeds and proper management of perennial grasses will inhibit the establishment of weeds. The most important preventative measure is to keep weeds from going to seed so that new infestations are prevented. Second, eradication is the removal of weeds from an area so they will not reoccur unless reintroduced.

Eradication is not usually possible on large areas but should be used for areas of 10 to 100 feet in diameter. The area must be replanted or another weed infestation will occur.

Third, control measures reduce weed populations to an acceptable level and should be the objective in all weed management plans.

There are four types of control measures:

  • Cultural methods, like prevention, promote the growth of desirable plants. Fertilization, irrigation, and planting high-quality desirable plants, allows plants to outcompete noxious weeds. Mechanical controls are the oldest control methods.
  • Mechanical measures involve disrupting weed growth by mowing, pulling, hoeing and burning. Biological controls involve the introduction of host-specific predators from the weed’s native country and the use of animals such as sheep and goats to reduce the vegetative growth of weeds. In Douglas County, the brown-legged leafy spurge flea beetle, aphthona lacertosa, has been introduced on an experimental basis to control leafy spurge.
  • Biological controls should only be done under the direction of the Douglas County Weed Inspector and work only 30% of the time after a 3 – 5 year establishment period.  Chemical control methods use herbicides to kill weeds.
  • Herbicides are most effective when used in conjunction with other management techniques. Always read and follow label instructions with applying herbicides. A good weed management system integrates two or more of these methods into a plan of operation.

Of special concern in Douglas County is diffuse knapweed. Diffuse knapweed is native to degraded non-cropland and seashores from the Mediterranean. It thrives in the semi-arid west and can’t tolerate flooding or shade. Diffuse knapweed has been reported to contain chemicals that can suppress competitive plant growth. Environmental disturbances encourage its invasion. The key to management is to prevent it from going to seed. A
single knapweed plant can produce 500 – 1500 seeds! Seeds are disbursed by the wind, as the plant dries, it breaks off and becomes a tumbleweed, allowing seeds to be disbursed over large areas. The dried stalks can lodge under vehicles, which spreads the seeds even further. Diffuse knapweed invades overgrazed pastures, forms dense stands and may be toxic to horses. Herbicides should be used in the spring or fall, and then the pasture area should be allowed to recuperate by not grazing for a season or longer as needed. If grasses do not return it should be re-seeded so grasses can compete with any surviving knapweed plants.

Become a better neighbor

  • Learn to identify the noxious weed species that are invading the area where you live and work
  • Report the location of all known and suspected noxious weeds to local managers so they can be dealt with quickly.
  • Understand the negative impact that weeds have on the environment.
  • Manage noxious weeds on your property by developing a weed management control plan to implement over time. Share your concerns about noxious weeds with your neighbors.
  • Minimize ground-disturbing activities on your land and always re-plant with desirable plants.
  • Use integrated weed management techniques for the effective and safe management of noxious weeds.