Adapted from City of Austin Invasive Species Management Plan Field Resources Manual.
Best Management Practices
Best Management Practices for control of problematic vegetation are based on Integrated Pest Management (IPM) principles that will maintain the desired site conditions using a combination of available methods, while minimizing risk to people, property and the environment. Managers use current information on pest life cycles and control methods to select the least toxic control method that is effective and economical. IPM plans identify current infestations, set action thresholds for treatment, and prescribe control and prevention methods. These principles include:
The determination of a treatment prescription and application method will take into consideration the situation, location and surrounding vegetation. Adjustments will be made, as needed, to accommodate special circumstances related to the facility location and adjacent environmental conditions.
When a Best Management Practices option indicates that pesticide applications are appropriate, control treatments will favor effective low volume applications of the least toxic and effective pesticides.
Elements and Tasks of an Invasive Plant Management Program
Step 1. Make a plan.
Step 2. Prevent entry and spread.
Step 3. Eradicate, control or contain, and monitor results.
Effective Treatments for Integrated Management of Invasive Plants
A successful invasive plant management program usually involves a combination of treatment methods based on these and other available tools and resources:
Many methods are available to manage invasive plants and rehabilitate sites and more are being developed. A successful plan of attack depends on integrated management that considers all methods relative to the site and its invaders. These methods will be presented in greater detail.
1. Cultural Methods
Proper cultural practices are essential in establishing healthy landscapes and can often help to maintain their resistance to pest problems. Several cultural practices, including prescribed burning and water-level manipulation, can reduce or control invasive plant populations. However, such practices may also have undesirable impacts to soils, animal habitat and native species, so care in planning and enactment must be exercised.
Prescribed Burning is a tool used for many facets of vegetation management. With regards to pest management, it may be used to manage both herbaceous and woody species. It provides the opportunity to accomplish vegetation management over a relatively large area at relatively low cost and target multiple species and individuals with minimal threats to non-target plant and animal species. When applied appropriately, prescribed burning can help significantly improve the effectiveness of other more intensive and costly treatments. Prescribed fire also avoids threats to water quality associated with use of chemical herbicides.
Prescribed burning is generally planned to target species that are susceptible to fire and do not exhibit re-sprouting behavior. Some re-sprouting species can be kept in check by prescribed fire when conducted on a recurring basis. Low intensity burns can be used to treat susceptible young or small-statured woody plants. High intensity burns may also be conducted to increase burn effectiveness on larger woody plants and King Ranch bluestem. for most herbaceous species, the timing of application of this practice must coincide with a particular phenological stage of the target species life cycle. For instance, when thistle plants are in the rosette stage or before annual species flower and produce seed. Winter or early spring burns are most effective for invasive forb species and King Ranch bluestem is best managed by summer fire.
Flooding or drawdowns can reduce invasive plant species in aquatic and wetland habitats but is usually not effective as a stand-alone treatment. This method is species and site specific. For effective outcomes, managers must first understand the biology of both invasive and native plants in the treatment area. Both processes can spread floating seeds of invasives and make habitats more vulnerable to nonnative plant establishment. Lowered water levels in spring and summer can also facilitate herbicide applications in wetlands.
Prescribed grazing is an approach that relies on cattle, sheep, goats or horses to reduce infestations. Grazing is a potential control treatment when the invasive is palatable and the invasive plant is not poisonous to the animal. Cattle and horses are used for many herbaceous invasive plants, while sheep and goats will feed on invasive woody plants as well. The animal species is important, as is the breed, the best being those breeds that are larger and can handle difficult grazing and browsing conditions. Grazers must be managed so that they do not selectively target palatable native species. Additionally, it is important to note that the animals would be used as a tool for vegetation management. A strict accounting of animal numbers, incoming and outgoing, must be provided so that animals are not allowed to remain on the property following the completion of work, becoming a management issue themselves.
Mulches and other ground coverings are often employed during the installation and restoration of landscapes as well as their ongoing maintenance. They are utilized for a variety of reasons. Mulches suppress weeds, help to retain moisture around plants, reduce possible erosion, and provide visual enhancement. Use of landscape mulches in vegetative buffers should take into account any possible impacts to the buffer as well as nearby waterways. These impacts may include:
Choices of mulches should take these concerns into account. Mulching in areas that are below typical high water lines is discouraged in any vegetative buffers. Seeding of cover crops for erosion control is allowed in buffer zones.
Soil solarization uses polyethylene sheeting to cover low growing, cultivated, mowed or chopped invasive infestations and trap solar energy to heat the soil and space under the sheeting to kill and suppress invasive plants. At least 2 years of summer cover are needed to suppress most invasives plants by 90 percent. other plants are killed by this method—it is not selective. Black sheeting is more effective than clear sheeting because it blocks needed sunlight, and, at an extra cost, is available with UV blockers to greatly extend the useful life of sheets to more than one growing season. The method is useful as a first treatment for relatively small areas and where herbicides cannot be used. Summer is the most effective season, and use on wet soils increases control. After removal, the bare soil is open for reinvasion and should be quickly revegetated or otherwise protected.
2. Manual Methods
Manual methods include hand pulling as well as use of a wide array of tools for cutting, chopping, wrenching and girdling invasive plants. Manual methods are generally used on woody invasive plants when they are small. Eradication is only possible when the root crown or roots that can resprout are completely extracted and seedlings are pulled or eliminated following seed germination. Because it is difficult and even impossible to extract all of the shallow roots, stolons, and rhizomes of many mature invasives, resprouting will usually occur. When this occurs, chemical treatment is usually required.
3. Mechanical Methods
Mechanical methods usually involve top removal or uprooting of individual plants. This method may be accomplished using hand tools, chain saws or heavy equipment. These methods can complement and increase the efficiency of herbicide treatments, followed by revegetation with desirable plants. Some equipment, with appropriate attachments, can prepare the site for seeding and tree planting. Most important is using the appropriate size equipment to meet job requirements and minimize damage to soils and streams. Timely follow-up with other control methods is essential, because disturbance of the soil creates favorable conditions for regrowth from seeds and root fragments. Mechanical removal with heavy equipment may be appropriate in natural areas. However, care should be taken and the use of heavy equipment should be limited or eliminated, in particularly sensitive areas (e.g. near streams or karst features).
Mechanical treatments will be applied in a manner that minimizes ground disturbance. Methods will be limited to those that allow selection of individual plants. These include use of hand tools, chain saws, and tractor or skid steer mounted devices such as tree shears and others. Less discriminating treatments such as chaining and root plowing will be avoided. Exceptions may be considered on a case-by-case basis.
4. Biological Control Methods
Biological control of plants uses living organisms to weaken, kill, or stop seed production of the targeted plant. The most common agents in bio-control programs are insects and pathogens. Uses of nematodes and mites are under study.
5. Chemical Methods
When other techniques are not sufficient, herbicide can offer an alternative. Effective herbicide applications can kill roots without exposing soil, though herbicide toxicity to non-target species and persistence, activity and mobility in soil or water must be considered. Exposed soil is susceptible to reinvasion and erosion. for successful herbicide treatments:
Selecting an Effective Herbicide
If a herbicide is not prohibited for use on a specific site then the broad category of non-crop areas even allows use in “non-used” lands and parks in urban and suburban environments. Some prescriptions for these other land types will also be given along with aquatic sites. Carefully read and study the herbicide label for information on specified areas of use, crops and prohibitions. It is not necessary for the target invasive plant to be listed on the label for permitted use if the label allows use for general weed control or control of broad categories, such as “annual weeds”,” perennial weeds” or ”woody species”. These more general uses are often discussed on the label under the heading of “non-crop areas”, “natural areas”, or “habitat management”. Additional sources of information on both effectiveness and toxicity include Material Safety Data Sheets (MSDS) that can be obtained from manufacturers and herbicide fact sheets. fact sheets are prepared by third parties and may contain additional information not found on the label or MSDS sheet. fact sheets, if used, should come from reputable sources.
Adjuvants and Additives to Herbicide Spray Solutions
Adjuvants are any product added to a spray solution to improve herbicide performance and effectiveness, including delivery, retention on foliage, and foliar or bark penetration. Adjuvants may be included as part of the commercial herbicide product or sold separately as an additive you must mix with the herbicide before application.
Choose an adjuvant, according to label recommendations, that is appropriate for your particular application method and field conditions. obtaining information about adjuvants and their effects can be difficult. MSDS sheets often the best source of information. Be aware that adjuvants may have more serious or long lasting environmental effects than the active ingredient of the herbicide, especially on aquatic organisms.
Another common additive used by professionals is a marking dye, which makes it easier to determine which areas have been sprayed and which still need treatment. Dyes marketed for this purpose will fade after a period of sunlight exposure.
Water Quality Protection
Water quality is an important environmental issue in relation to pesticide use. The strategies for reducing or preventing water contamination by these products are largely based on common sense. When applying pesticides, the applicator should read the product labels and use the lowest effective rate listed on the label for any one application. Calibrate equipment to deliver herbicides according to label recommendations and keep records of the amount of product applied. An applicator should NEVER “double the rate for better results” and NEVER deviate from strict label application rates.
The key to minimizing impact is reducing the levels of possible pollutants that enter the system. factors determining the potential for ground water and surface water contamination include tendency for the pesticide to attach to soil particles or organic matter, solubility in water, rate of degradation and volatility. Soil is a common pathway to groundwater and soil characteristics, along with the chemical’s inherent mobility, determine the rate at which chemicals move through the soil. Soils with high clay or organic- matter content are more likely to bind herbicide molecules, tying up the material while it is decomposed by microorganisms or other degradation processes. To minimize contamination due to runoff, do not apply products within 48 hours of expected heavy rainfall.
Pesticide drift can be controlled by spraying only on calm days, using lower pressure, larger droplet size and drift control additives in the spray solution to reduce spray drift. These precautions should be taken to reduce spray drift on all occasions. More detail on managing spray drift is given in the following section of this plan. The use of broadcast spray methods should be minimized in favor of more directed application methods.
One potential source of water contamination is the disposal of unused herbicide, product containers and rinse water. Prepare only the amount recommended for the area to be treated to prevent having unused herbicide at the end of an application. Rinse all empty containers, regardless of their type, three times before disposal. Do not dispose of container rinse water where it may flow into a waterway.
Instead, dispose of rinse water by application on the treated area. Dispose of the product containers according to label directions.
Selective Herbicide Applications
The best approach is usually selective applications to target plants while avoiding or minimizing application to desirable plants. The selective methods described below are directed foliar sprays and wipes, basal sprays and wipes, stem injection, cut-treat, and soil spots.
Directed foliar Sprays and Wipes
Directed foliar sprays are herbicide-water-adjuvant solutions aimed at target plant foliage to wet all leaves, applied by either low- or high-volume sprayers. Herbicide application by directed foliar spray is one of the most cost-effective methods for treating many types of herbaceous and woody invasive plant species. With this method, herbicide mixtures are applied to the foliage and especially the growing tips of woody plants, or to completely cover all leaves. foliar sprays can be applied whenever leaves are present but, for woody plant control, are usually most effective from midsummer to late fall.
Winter and spring applications are also effective in controlling some species and are often required to prevent seed formation.
Selective treatment is possible because the applicator can direct the spray towards target plants and away from desirable plants. The addition of a spray shield to the end of the wand confines spray to the target. Another safeguard is to only use foliar-active herbicides, because directed sprays of soil-active herbicides can damage or kill surrounding plants when their roots are within the treatment zone. Never use herbicides with soil activity to treat invasive plants under desirable trees or shrubs that are susceptible to the herbicide. If non-target foliage is accidently sprayed, clip off the foliage to prevent uptake.
Low-volume foliar sprays using spray tips and spraying pressures of 20 to 30 pounds per square inch can ensure productivity and limit drift. Wind must be minimal (less than 10 miles per hour) and used by the applicator to facilitate upper crown coverage. Low wind can be dangerous because it is variable and unpredictable, wind speeds of 5-10 mph is optimal.
Directed foliar sprays can be applied in higher volumes by using spray wands attached by hoses to vehicle-mounted spraying systems that have much larger herbicide tank capacities. The high-volume directed foliar spray is the most efficient approach to large infestations of multiple invasive species where there are few non-target plants.
Handheld weed wicks and rollers apply ultra-low volumes by wiping the herbicide mix onto the target leaf surfaces or bark; the herbicide mixture is contained in the handle. Most wick systems have limited use and durability in forest and field situations, but are useful when the applicator needs to avoid applying herbicide to rare or protected plants. Vehicle mounted wipe bars can be used to selectively target large areas of taller target species (e.g.- Johnsongrass) with minimal impacts to shorter desirable species.
Basal Sprays and Wipes
Basal sprays are herbicide-oil-penetrant mixtures sprayed on the lower portion of woody stems. The sprays are usually applied with a backpack sprayer or wick applicator. Avoid spray contact with desirable trees or heavy use within their root zone. The herbicide must be an oil-soluble formulation and mixed with a special basal oil product, penetrating oil, diesel fuel, fuel oil, mineral oil, vegetable oil with a penetrant, or blends of these ingredients.
The most effective time period in most of the South for a basal spray and streamline is June through September, while winter treatments are easier when leaves do not block access and spray. After treating with a basal spray, wait at least 2 years before disturbing aboveground plant material, because herbicide activity within plant roots can continue for an extended period.
Stem injection (including hack-and-squirt) involves the use of mechanical herbicide injectors or the application of herbicide concentrate or herbicide-water mixtures into downward incision cuts spaced around woody stems and often made by a hatchet or machete. Tree injection is a selective method
of controlling larger trees, shrubs and vines with minimum damage to surrounding plants. Injection treatments are sometimes not as effective in controlling multiple-stemmed species compared to the faster basal bark treatments, but may be easier in remote or rough terrain where a backpack sprayer might be impractical or cumbersome. Incisions should be spaced around the stem, deep enough to penetrate the bark and inner cambium, slightly into the wood. Do not make multiple cuts directly above or below each other because this will inhibit movement of the herbicide within the stem. A complete girdle or frill of the stem is not needed or desirable.
Cut-Treat or Cut-Stump
Cut-treat involves applying herbicide concentrates, herbicide-water or herbicide-penetrant mixtures to the outer circumference of freshly cut stumps or the entire top surface of cut stems. Applications are made with a spray bottle, squeeze bottle, backpack sprayer, wick or paint brush. freshly cut stems and stumps can be treated with herbicide mixtures to prevent resprouting and to kill roots. It is critical that the cut is made as low as possible to the ground, and that the stem is treated immediately after thecut is made. To minimize deactivation of the herbicide in the cut-treat method, remove sawdust from stumps before treatment. for stumps over 3 inches in diameter, completely wet the outer edge with the herbicide or herbicide mixture. Make certain that the solution thoroughly covers the wood next to the bark of the stump. Completely wet the tops of smaller stumps and all cut stems in a clump. Note that some herbicide labels advise treating the outer portion of the stump down to the ground.
Broadcast Herbicide Applications
Broadcast application of pesticides will be avoided. However, in rare cases in which broadcast application is deemed appropriated, chemicals should be selected that have low-non target toxicity, low potential for movement and a short half life in the environment. The Texas Agricultural Extension has developed a list of recommended chemicals for broadcast application with these characteristics.
6. Strategic Control Method: Combination of Control Methods
The most appropriate, effective and safest control of a target pest is a strategic combination of several of the control methods outlined above, integrating herbicides into the available management methods.
The combination of various manual, mechanical, and chemical methods is often the Best Management Practice for cost-effective and environmentally safe management. All options involving chemical control methods will be in strict compliance with product label requirements.
The proposed use of chemical controls in the following instances must be reviewed and approved by the City of Austin IPM Coordinator prior to their use:
7. Rehabilitation, Restoration, and Reclamation
Once invasive species are removed, plants and animals can recover. However, natural recovery processes can be overwhelmed by invasive species and restoration is required. Although restoration efforts have common elements, each area is unique. Work must be guided by site-specific considerations and analysis. However, some generalizations can be made. When soil is disturbed, and especially if it is left bare, it must be revegetated with appropriate species to prevent soil loss and reinvasion. Below is a discussion of some of the factors to consider in a restoration project, followed by a generalized protocol for rapid revegetation of an upland site.
The goal of restoration is to restore ecosystem process, not simply to replace components. Ecosystem processes allow natural systems to repair themselves and to remain relatively stable. The primary processes of concern to a manager are hydrology, nutrient cycling and energy capture. In practice, the assessment and repair of these processes begins with the soil. In the process of treating and removing invasive species, the soil may be disturbed and left bare. In some cases, compaction reduction activities (raking, tilling, disking, ripping) and organic soil amendments may be needed to restore soil to a useful state. In all cases, soil should be protected. Revegetation with appropriate native species provides permanent protection, but in some cases temporary soil protection measures such as mulch may be needed before the site can be revegetated.
Generalized revegetation protocol: