FAQs

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How do I obtain my license to apply herbicide? 

State law requires a special license for anyone who supervises applicators, gives out advice on herbicide, uses restricted use products (Tordon), or does commercial pesticide work.  These are the two types Qualified Supervisors (QS) and Certified Operators (CO).  If your interested in getting you license go to the Colorado Dept. of AG website for more info. you will need to obtain educational material (available for loan at the county weed office), register with the state, apply, and set up a time and place for your exam.  The nearest testing facility is in Cortez.

For information about native and noxious weeds, where can I go?

 
Here are some online resources relating to Noxious Plants:

Who can I hire to spray my weeds?

Where can I learn more about herbicide affected compost?

"No Spray" - How can I list my property as "No Spray"?

What should I do with herbicide I no longer need?

    The County Weeds Dept. cannot accept herbicide donations at this time.  The County sponsors a Household Hazardous Waste Collection event in even numbered years. This information will be updated as possible.

What kind of herbicide should I use and when do I spray?

    There are different herbicides for different types of weeds.Our (choose type and then follow link to info sheet) for each enforceable species gives several recommendations for herbicides as well as the ideal time for spraying.

What are Invasive Ornamentals?

    There are several noxious weeds that have attractive looking flowers, but are highly invasive. These "escaped ornamentals" were introduced as flowers for gardens or as part of wildflower mixes and can spread rapidly. has white petals with a yellow center and is often confused with wildflowers.  and (both have yellow flowers) are often found in planters and escaping/spreading into nearby soil.  has a snapdragon flower and can be mistaken for an ornamental or wildflower, and can grow at higher elevations above timberline.  is a sage looking plant with small yellow flowers that appear late in season, and has been used for landscaping because of its ability to flourish with very little water.

How do I report problem weeds?

Does the "Herbicide Cost-Share" program still exist?

Unfortunately no. 

Due to budget cutbacks the County discontinued this program.  It is uncertain if this program will be reinstated in the future.

What weeds can be controlled effectively by hand pulling or digging?

  • Mowing does not have the same effectiveness as hand pulling or digging.
  • Hand pull or dig when soil is moist.
  • Hand pull or dig before flowering occurs, usually around June or July.
  • If removed during or after flowering, bag and dispose of plants carefully so you will not scatter seeds.

Absinth wormwood- Make certain to pull all the roots, including short horizontal roots.

Musk, Scotch, Bull thistles- Cut tap root two inches below ground to prevent re-growth.

Houndstongue- Cut taproot two inches below ground to prevent re-growth.  Old seed stalk:  Prior years dead plants with hanging seeds can be carefully cut at the bottom of the stalk then bagged.

Spotted knapweed- Be sure to hand pull or cut taproot at least 5 inches below soil to prevent re-growth before flowering and seed formation.

Oxeye daisy and Scentless chamomile - (recommended for new or small infestations) Hand pull or dig when soil is moist.  Oxeye is fairly shallow rooted- make sure to pull up all of the roots.

Myrtle and Cypress spurge- Make certain to pull all the roots.  Be careful and wear rubber gloves and eye protection, as the milky sap is caustic.

What kind of thistle do I have?

There are 3 main thistles in La Plata County. Scotch thistle is very big and spiny with large gray/green leaves and large purple flowers. Musk thistle is tall, but have darker and smaller green leaves/stems with symmetrical leaves. They have single pinkish/purple flower heads.  Canada thistle grows relatively shorter but in thicker stands, and have clustered seed heads with multiple, small pink flowers.  Canada thistle is prevalent near waterways, such as riversides, irrigation canals, fields and ponds, although it can also be found in dry sites.  Bull thistle has a unique leaf shape, which is narrow, spine-tipped, and progressively narrower at the tip.  The leaves are also dark green and have fine hairs.  Scotch, Musk, and Bull thistles are all biennial; meaning the first year the plant is a small rosette, without flowers.  The second year the plants produces seeds via flowers then die.  Canada is a perennial, meaning it lives year after year.

Is mowing an effective way to control weeds?

For the most part, no.  Mowing can actually increase shoot density of some plants with a creeping root system.  Research has shown that several mowings on Canada thistle will introduce stress and set up the plant for a fall-applied herbicide.

After being cut, most weeds will re-grow shoots from the reserves in the roots back into the upper plant in order to make flowers and seeds.  Certain plants can even create multiple stocks or heads where one was cut off, thus increasing the seed count.  When controlling a bi-annual seed production plant, like Musk thistle, the root should be cut one to two inches below soil surface prior to flowering, which will kill the plant.  Preventing flowering and seed formation is critical for success for plants that only spread by seed.

Some studies have shown that after years of repeated mowing at the right time can eventually exhaust a plants reserve in the root system.  However this is not recommended unless you plan on mowing multiple times a season.

Is tilling an effective way of controlling noxious weeds? 

Not unless you have annual or bi-annual seed producing plants, and till before they produce seeds.  Tilling can actually profoundly increase the size and density of weeds if used on root spreading plants like Canada thistle and Leafy spurge because the individual root segments will grow into separate plants.  Tilling the soil can also invert the topsoil with sub soils, which may be of lesser quality soil.

I believe a pesticide was misused, how can i report this? 

There are state and federal laws governing the legal use of pesticides. The best way to verify the correct use of pesticide, is to read the product label. This is a legal document which defines the correct use of pesticides and herbicides. IF YOU DON"T FOLLOW THE LABEL YOU ARE BREAKING THE LAW. If you have questions, call 970-382-6470. You can also find out more info and file a complaint here, https://www.colorado.gov/pacific/agplants/pesticides