Different Tools can be Used to Control Noxious Weed Infestations

Using low amounts of herbicide mixed with water and applied with either a backpack sprayer or an ATV/UTV is an effective and fast way to control weeds.  Results using herbicide will be noticed within the first treatment year, which will allow healthy vegetation to establish relatively quickly compared to other management methods.  

Many herbicides are very specific or ‘selective’, which means the chemistry is designed to only affect the target weeds, with little to no effect on desirable vegetation.  Other herbicides, such as Glyphosate (Round Up) are considered a general, non-selective herbicide and will kill or wilt all plants that come in contact.

When performing rangeland restoration, WMA Specialists uses proprietary methods (prescriptions) that selectively target noxious weeds by using selective herbicides.  These herbicides target specific broadleaf weeds (dicots). By reducing the undesirable vegetation with selective herbicides we can promote healthy understory vegetation that will provide competition against germinating weed seeds.  

Herbicide rates, mixed correctly, will have a detrimental effect on noxious weeds but allow native wildflowers, forbs and grasses to return to their native range.

Herbicide treatments can be performed any time during the growing season.  We recommend treatments to be performed from May through October.

Each project area may vary depending on location, aspect and species present.  A treatment schedule may vary due to elevation, weather and rotational schedules; therefore, the perfect application time for your property will be scheduled.

This method uses mowing, cultivation, shoveling and/or hand pulling to remove certain plants and reduce the seed bank from an area.  This method works well on smaller project areas and for annual, biennial and tap-rooted plants. In other cases, mechanical control is discouraged and counter productive on rhizomatous weeds such as leafy spurge, toadflax, Canada thistle, common tansy and a few others because it can promote growth.  Knowing the phenology of the noxious weed in question is a prerequisite to choosing the proper management technique.   

Mechanical control can work well controlling annual, shallow-rooted and tap-rooted species such as cheatgrass, bulbous bluegrass, medusahead, spotted knapweed, houndstongue, blueweed, hoary alyssum, and more.

This method is most commonly used on large, continuous infestations or hard to access areas where herbicide and mechanical treatment is not cost effective.  Bio-control uses insects that are natural predators to the specific weed in need of control.  This is a very effective and affordable control but the results are slow and will take years before they are visually noticed.

Different varieties of weevils and beetles may attack different parts of the plant.  Some feed on the seed head, some feed on the root and others may defoliate the weed. Knowing what noxious weeds are present and how they propagate can help you choose the correct species of insect for the noxious weed infestation on your property.

The USDA Animal and Plant Health Inspection Service (APHIS) have approved a variety of insect species for release in our area.  Listed below are only a few of the approved biocontrols:

Cyphocleonus achates – Knapweed Root Weevil

Mecinus jathiniformis – Dalmatian Toadflax Stem Weevil

Ceutorhynchus litura – Canada Thistle Stem Weevil

Aphthona nigriscutis & Aphthona lacertosa – Leafy Spurge Flea Beetles

Other biocontrols exist and are approved for release by the USDA.  For more information visit here and here.

Typically, an area will need to be reseeded if there is less than 30% desirable vegetation within the project area.  The idea behind reseeding is to use early germinating, fast growing native grasses and forbs to create competition and close off open niches where noxious weeds will grow.  Timing is crucial, along with normal to above normal annual precipitation. A wet, cool spring proves to have higher success. 

Seeding schedule with weeds present:

Ideally, weeds are treated using herbicide in the spring and depending on the prescribed herbicide, seed is distributed in the fall prior to the first snowfall.  Many of the species used will consist of cool season annual and perennial grasses.  Some seeds, such as wildflowers and certain forb species will need to go through a scarification (freeze/thaw) period. These seeds will need to be cast well before the spring.  Choosing the correct seed mix will promote competition and with success will be the first thing out of the ground in the spring.  This is especially important in cheatgrass stands.

A typical seed mix will have a variety of species composed and formulated to match the historic, native plant community previously inventoried on your property.  

If a landowner or manager chooses to treat noxious weeds with herbicide, our professional recommendation and reseeding mantra is to remove the undesirable species prior to seeding.  This will allow a non-conflict approach that will prohibit herbicide damage to desirable seeds cast.