MACC Invasive Species Front Page
Introduction to Invasive Plants
Conservation Commission Jurisdiction of Invasive Plants
I.D., Ecology and Control of Invasive Plants
Site Invasive Plant Restoration and Replanting
Funding for Invasive Plant Control
Discuss Invasive Plants On-Line
 

Control using Herbicides

This web page provides an overview of the techniques that are commonly used to control invasive plants with herbicides. MACC recognizes many concerns regarding the application of herbicides, and discourages the use of herbicides unless they are deemed the only feasible option to achieve control. In situations where use of herbicides is the only feasible control method, MACC supports their use, provided such use is carefully planned, permitted, and monitored.

Herbicide use and application methods are regulated by state and federal laws -- the pesticide label is the law. It is the responsibility of the landowner and any employees or contractors to adhere to state and federal pesticide laws at all times.

Pesticide Licensing
Chemical herbicides are a common method of controlling invasive plants. Herbicide use is carefully regulated by the state of Massachusetts and by Federal laws. In general, landowners can apply unrestricted herbicides on their own property outside of the wetland buffer zone; permits may be required within the buffer zone. A pesticide applicator’s license is required to apply restricted pesticides, or to apply any pesticide on land owned by another.

For information on the different pesticide categories and for specific information on the laws governing the use of pesticides in Massachusetts please visit:

Common Herbicide Application Methods
The method one uses to apply herbicide depends on such factors as target species, site characteristics, herbicide type, and time of year. Wetland approved herbicides are required near waterways in accordance with state and federal regulations. The most common herbicides used for invasive plant control are systemic herbicides, although other herbicide types are available and may be appropriate. Systemic herbicides kill the plant by being absorbed into, and translocated throughout the plant tissue. It is important to apply herbicides when the plant is translocating carbohydrates (sugars) down to the roots (from early summer to early winter). It is also important to apply enough herbicide to the aboveground parts of the plant to kill all the roots. With the cut-stump method, concentrated herbicide is applied to a small surface area on the top of the freshly cut stump. Conversely, with foliar spray, a low diluted herbicide is applied to a large surface area (all the leaves). Foliar spray will not kill the plant if it is applied only to a small percentage of leaves. Regardless of method, it is important not to cut stems or roots of target plants for at least 6 months to a year after the herbicide is applied. Herbicide takes months to work its way through the plant’s vascular system, and cutting may disrupt its flow to living tissue.

  • Foliar Spray: Foliar application of herbicides entails spraying the leaves of target plants during the growing season with a low concentration of herbicide (approximately 0.75–3%) in water. Marking dyes, anti-drift formulations, and surfactants should be added in accordance with the pesticide label. The spray can be applied with a hand-powered, backpack sprayer or larger, motorized sprayers. Foliar spray treatments should be conducted during the growing season, between early July and mid-September. At all times, applicators should be aware of herbicide drift. Applicators should spray with their back to desirable vegetation, sensitive areas, and waterways, and avoid spraying during windy days. Lowering tank pressure and setting the nozzle opening wider (more stream than spray) will lessen the potential for drift. If spray contacts the foliage of desirable vegetation, immediately cut off the affected leaves or branches to minimize the absorption of herbicide. One should avoid spraying tall vegetation. In addition, the herbicide can take many months to travel from the leaves to the roots; therefore, it is important to wait at least a year before cutting the stems of woody vegetation treated with foliar spray.

  • Cut-stump: The cut-stump method entails cutting vegetation near the ground and applying concentrated herbicide to the stump or stumps (in the case of multiple stemmed plants). Herbicides should be applied immediately after the cut is made and should cover the plant’s cambial tissue around the rim of the stem. Marking dye should be added to the herbicide to indicate which stems have been treated. Cuts often are made with hand saws or pruners, but chainsaws or gas-powered brush saws may be used on larger stems. Herbicide may be applied with paint brushes, squirt bottles, foam applicators, and mechanized applicators mounted on brush saws. The cut-stump method is time consuming, but it is very selective. It should be used near sensitive, desirable vegetation and on target plants that cannot be foliar sprayed without a high risk of drift (e.g., tall shrubs, trees, or vines). The cut-stump method can be used any time the plant is translocating sugars through the cambium down to the roots. The general period for this activity is from early July through November, although there is some evidence that fall application is more effective.

  • Basal Spray: The basal-spray method involves the application of an oil-based herbicide to the bottom portion of a plant’s stem. The oil penetrates the plant’s bark and carries the herbicide into the cambium for translocation to the roots. Basal treatments generally are applied using a sprayer at low pressure with a marking dye. The concentration of herbicide in oil is dependent on the product being used and the application type. Consult pesticide labels for treatment methods, mixture instructions, and site restrictions. The basal-spray method is similar to cut-stump application in that it is highly selective and may be used from early July through December. It tends to be faster than cut-stump because cutting is not required, but may require the application of more active ingredient. Basal spray formulations can also be applied to cut-stumps that have begun to re-sprout.

  • Aquatic Herbicide Applications: Herbicide use in aquatic environments is carefully regulated by the state. Applicants must meet the requirements of a BRP WM 04 license. For a description of the permit process please see page 8 of Guidance for Aquatic Plant Management in Lakes and Ponds as it Relates to the Wetlands Protection Act. For a thorough description of aquatic herbicide use please see Section 4.6 of Massachusetts DCR’s Generic Environmental Impact Report (GEIR)

  • Reducing Non-Target Kill: It is important to avoid the unintentional killing of non-target plant species. Nevertheless, it should be expected that some non-target kill will occur. Application guidelines to reduce herbicide drift are outlined on the product label. Several tools are available that apply the herbicide in a targeted manner. Reviews of select tools are available at this website. Use common sense and caution at all times. Invasive species may form root grafts with desirable native plants. While not common, herbicide applied to an invasive plant might be translocated through the roots and damage non-target vegetation.

Additional Resources on Control Methods
The following websites provide a wealth of information about invasive species control methods.