Weed Control

Traditional weed control has typically focused on one method to control weeds – herbicides. The Uintah County Weed Department relies on the IWM approach to weed control. IWM stands for “Integrated Weed Management” a method of weed, control that utilizes two or more types of controls to eliminate a certain weed. There are four basic types of controls we can use to control weeds – herbicides, biological, mechanical and cultural. Weed control is often more effective when two or more of these controls are used together.

Herbicides are chemicals that affect the ability of the plant to grow properly. Some herbicides are applied prior to seed germination that inhibit the plants ability to sprout. Most herbicides are applied to the actively growing plant. The plant then absorbs the herbicide through the foliage, stems/bark and/or roots. These herbicides affect the chemical balance of the plant causing growth irregularities which in turn kills the plant or destroys its ability to reproduce. Herbicides are engineered to affect certain classes of plants – some being selective killing only broadleaf or only grasses and others being non-selective which may kill any plant it touches. Non-selective herbicides, such as Roundup® (glyphosate), used carelessly, often open up areas for noxious weeds to invade by removing beneficial competitive plants. Herbicides must be used cautiously to avoid off target damages that may occur to beneficial plants, animals, or yourself. Be sure to read and follow all label directions and precautions to ensure proper results.

It is also important for people to get away from the 2,4-D mentality. 2,4-D continues to be an effective herbicide but recent technology has produced many specialized herbicides that are far more effective than 2,4-D alone for many noxious weeds. Although these herbicides may be far more expensive than 2,4-D, they may save you money in the long run because they can drastically reduce or eliminate the weed problem which requires less inputs in the future. Less herbicide put on the land is better for your business and the environment. Contact the Weed Department to learn about other herbicides.

Surfactants. As important as selecting the proper herbicide is, selecting and using a high quality surfactant is vital to the success of your weed control program. Weeds have many defenses against herbicides such as waxy cuticles, pubescence (the tiny hairs on the leaves and stems), extensive root systems among other things. Surfactants break down water tension allowing the herbicide to spread across the weeds surface and be translocated into the weed more effectively. Without the surfactant most, if not all, the herbicide will run off or evaporate before it can be absorbed. Yes, surfactant cost more money, but without it you simply will not get anywhere near the full potential from your expensive herbicides and you will be wasting money.

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Biological controls are the natural enemies of noxious weeds. Since most noxious weeds have been introduced from foreign countries these weeds have few if any natural controls (insects, pathogens, large herbivores etc.) to keep them in balance with their new environment. With no natural control many of these weeds are able to compete aggressively with native vegetation disrupting agriculture, recreation, transportation, wildlife and soil and water quality. Animal and Plant Health Inspection Service (APHIS) is working to bring select natural enemies (typically insects and pathogens) of noxious weeds to the United States. APHIS tests each possible bio agent and possible mutations for a period of 5 to 7 years to ensure the agent will not harm any beneficial vegetation. Biological controls are not meant to eradicate noxious weeds but they are an important management tool for select weeds that are beyond control due to infestation size, inaccessibility, and/or herbicide resistance. Biological controls being used in Uintah County include:

Field bindweed Gall Mites — Aceria malherbae have been introduced near Jensen, Utah and appear to be having significant impact on field bindweed near the release site.

Musk thistle Seedhead Weevils and Beetles — Trichosirocalus horridus a stem borer weevil and Rhinocyllus conicus a seedhead weevil (below) are biocontrol insects that have been widely introduced in Utah. These insects now spread very well on their own and they can be found throughout Uintah County.

Leafy Spurge Flea beetles — Three species of flea beetles, Apthona nigriscutis (below left), A. flava, A. Czwalinea, have been introduced to the counties leafy spurge population in 2008.

Long horn stem beetle — Oberea erythrocephala (below right) have also been released on the leafy spurge population in 2008.

Saltcedar (tamerisk) Leaf Beetle — Diorhabda carinulata (formerly D. elongata) (Below) have been released on several sites along the Green River in Uintah County. Adults (5-6 mm) emerge in May and June and begin laying eggs. Larvae emerge in about a week. Larvae morph through 3 instars (1^st - 2 mm, 2^nd - 4 mm, 3^rd - 9 mm) over 21 days then pupate into adults in ground litter. Adults live for 15-20 days. When well established, D. elongata may defoliate up to 1/2 mile of saltcedar per week.

Goats and/or Sheep — Leafy spurge (right) and Russian knapweed are being controlled using either goats or sheep in Uintah County. Goats and sheep have gained weight readily on a diet of noxious weeds. They must be strictly confined to the areas of weeds so they will feed on the target species and they soon gain a taste for the "undesirable" vegetation.

Mechanical controls involve the use of machinery to disrupt the life cycle of weeds. Plowing, digging and hand grubbing can be affective on select weeds. Annual and biennial weeds are most susceptible to these methods. Mechanical control is not normally a good option for Perennials. Perennials often benefit form these disturbances since they may reproduce from broken plant parts.

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Cultural controls utilize competition to control weeds. Many weeds can be controlled, but not usually eradicated, by planting and cultivating other competitive vegetation that is able to compete for available resources. This practice is commonly used following wildland fires to prevent noxious weeds from re-establishing too rapidly or easily.

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