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Recommendations for chemical control of noxious weeds using backpack and hand held sprayers
- IPM
- A successful weed control program must incorporate Integrated Pest Management. IPM combines chemical,
mechanical, cultural, and when possible, biological control methods.
- Safety
- Always use herbicides with care and follow the label recommendations for mixing and applying herbicides.
- Revegetation
- Replanting desirable vegetation to a control site may be required in order to discourage reinfestation of
noxious weeds and compete with seed banks that may be present in the soil. Bare ground provides ideal conditions for
noxious weeds.
- Timing
- Timing is very important when using herbicides. Improper timing is the main cause for herbicide failure. Young,
healthy, actively growing plants are usually most susceptible to chemical control.
- Surfactant
- Surfactants aid in the coverage and penetration of herbicides on the plant surface. Adding a non-ionic
surfactant to the tank mix is highly recommended because it can significantly improve the efficiency of the
herbicide. Your chemical dealer or County Weed Board can recommend a good non-ionic surfactant.
- Herbicides
- Your chemical dealer or County Weed Board can recommend herbicides for your particular situation. Many
herbicides can be purchased by most adults while others require the purchaser to have a pesticide applicator
license. Non-Selective herbicides generally target all plants including grasses while Selective Broadleaf herbicides
target broadleaf plants and generally do not harm grasses. If you are interested in obtaining an applicator license
contact the Kittitas County WSU Extension Office for information and study materials.
Always use herbicides according to their label and instructions.
- Brash® and Weedmaster® - are combinations of two Selective Broadleaf Herbicides (2,4-D amine + dicamba).
- Generally labeled for Pasture, Rangeland, Hay, and General Farmstead.
- Can be purchased at local farm supply and chemical retailers (no applicator license required on
purchases of one gallon or less).
- Mix according to the label for specific needs (generally 1 ounce per gallon of water or 2 to 4 pints per
acre) and add surfactant.
- Crossbow® - is a combination of two Selective Broadleaf Herbicides (triclopyr + 2,4-D ester) with moderate
residual activity.
- Generally labeled for Pasture, Rangeland, and Non-cropland.
- Can be purchased at local chemical retailers (no applicator license required on purchases of one gallon
or less).
- Mix according to the label for specific needs (generally 1 to 2 ounces per gallon of water or 2 to 4
quarts per acre) and add surfactant.
- Milestone® - is a Selective Broadleaf Herbicide (aminopyralid) with long-term residual activity.
- Generally labeled for Pasture, Rangeland, and Non-cropland.
- Can be purchased at local chemical retailers (no applicator license required).
- Mix according to the label for specific needs (generally .07 to .16 ounces per 1000 sq ft or 4 to 7
ounces per acre) and add surfactant.
- Tordon 22k® - is a Selective Broadleaf Herbicide (picloram) with long-term residual activity.
- Generally labeled for Pasture, Rangeland, and Non-cropland.
- Can be purchased at local chemical retailers (applicator license required)
- Mix according to the label for specific needs (generally ½ to ¾ ounces per gallon of water or 1 to 2
pints per acre) and add surfactant.
- Noxious Weeds
- Knapweed, Kochia, and Canada thistle are three of the more common noxious weeds in Kittitas County. For a
complete noxious weed list and other useful information visit the Kittitas County Noxious Weed Control Board website
at http://www.co.kittitas.wa.us/noxiousweeds or contact them at (509) 962-7007.
- Knapweed
Rosette to early bolt stage is most vulnerable to herbicides making spring or early summer the best time to
treat knapweed. Most broadleaf herbicides are effective in controlling knapweed with proper timing. Treat plants
before flower bloom to be most effective. Flowering plants may require mowing to prevent seed production but
regrowth will occur. Plant regrowth can be effectively treated with herbicides. Follow-up treatments may be
required for missed plants and reintroductions. Fall spraying with residual herbicides can also be very
effective for knapweed control. Hand pulling can be effective for smaller populations.
- Kochia
Plants 12 inches and less are most vulnerable to herbicides. Treat plants before maturity to be most effective.
Some herbicides effective in controlling kochia include 2,4-D, Dicamba, MCPA, Fluroxypyr, and Chlorsulfuron.
Tank mixes of more than one effective herbicide will provide more complete control and discourage proliferation
of herbicide resistance bio-types in successive generations. Up to four treatments per year may be required to
control multiple, delayed seed germinations. Mowing can be effective if done before seed production.
- Canada Thistle
Treat in early bud stage and when regrowth reaches 6-8 inches. Some herbicides effective in controlling Canada
thistle include Aminopyralid, Picloram, Clopyralid, 2,4-D+Dicamba, and Chlorsulfuron. Well established stands of
this perennial may have an extensive root system requiring repeated herbicide applications. Fall applications
with residual herbicides can be very effective in discouraging regrowth the following year.
- Hand Held Sprayers
- A quality backpack or hand held sprayer can be purchased at local farm supply and hardware stores for a
reasonable price and will last for years if maintained properly. As a public service to private landowners the
Kittitas County Noxious Weed Control Board loans out back pack sprayers free of charge on a first come, first serve
basis. Call (509) 962-7007 for availability.
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