Aerial Herbicide Application for Brush Control Information Fact Sheet
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An important economic consideration in the management of Alberta’s tame pastures is controlling the amount of woody plants such as trees and shrubs (also called brush encroachment). In low cover amounts, woody plants on tame pastures can provide complimentary livestock forage, provide shade, act as a snow trap, and provide benefits to wildlife. However, in higher amounts (increased density, diameter, height and cover), woody plants often become competitive and reduce the forage productivity of the tame pasture. In turn, this result can reduce grazing benefits and increase pasture management costs. In situations where woody regrowth is competitive with grazing interests, a number of management control options are available, such as biological (e.g., federally registered brush control herbicides).
The recent ability to aerially apply a variety of herbicides to control shrub and tree encroachment on tame pastures on grazing dispositions (leases, permits, licences) and Provincial Grazing Reserves (PGR) has raised a number of questions concerning approvals, safeguards to protect the environment, and application method(s). The purpose of this fact sheet is to assist grazing disposition holders and PGR Associations with awareness and planning considerations necessary to improve the control of brush on tame pastures and eliminate the risk of herbicide drift into sensitive, environmental areas.
The use of herbicides to control woody plants on tame pastures is considered one of the tools in the brush control toolbox. As such, this tool should be carefully planned out, integrated with other tools to increase cost effectiveness, and incorporated into the overall grazing management plan. Herbicide application for brush control is considered a range improvement project, and as such, must receive written authorization from Lands Division through the local Range Agrologist or Provincial Grazing Reserve Manager. The approval will be based on directions provided in a range improvement or range development plan that would be developed following referrals to other affected resource agencies. The conditions for herbicide applications will be included in the approved plan. These conditions must be signed off by the Lands Division representative or PGR Association representative. For aerial applications (the focus of this fact sheet), the licensed aerial applicator will also be required to sign off on the approval conditions.
Typical Herbicides used in Aerial Applications:
Picloram and 2,4-D (commonly known as Grazon* Herbicide)
Triclopyr (commonly known as Remedy* Herbicide)
Dicamba (commonly known as Banvel** Herbicide)
2,4-D (for example, 2,4-D LV ester 600)
* Grazon is a trademark of Dow AgroSciences LLC
* Remedy is a trademark of Dow AgroSciences LLC
** Banvel is a trademark of BASF Canada
Details on the efficacy, use and restrictions of all registered agricultural herbicides can be found in the manual published by Alberta Agriculture, Food and Rural Development called "Crop Protection 2003"; (AGDEX 606-1). Information is also available from the manufacturers (Contact information found on Pg. 1 AGDEX 606-1), and on labels.
NOTE: The choice of herbicide will be dictated by the species you are attempting to control, the desired end result, and taking into account any and all risks associated with residual effects, soil type and site sensitivity.
Relevant Legislation:
- Environmental Protection and Enhancement Act
- Pesticide (Ministerial) Regulation (AR 43/97)
- Pesticide Sales, Handling, Use and Application Regulation (AR 24/97)
- Code of Practice for Pesticides (incorporated by the Pesticide
(Ministerial) Regulation and the Pesticide Sales, Handling, Use and
Application Regulation, under the authority of Section 36 of the
AEPEA).
Definitions:
Drift: The adverse affect caused by unintentional offsite deposition of herbicide. Drift can be caused by fine spray droplets displaced by wind, spray pattern, or temperature inversions. The potential extent of drift must be accounted for when selecting nozzle size, droplet size, height of application and location of the spray zone.
Excursions: The effects of herbicide application visible outside the boundary of the spray zone; can be a result of the aerial operator forgetting to turn off the spray, a mechanical malfunction, or it could be the result of drift.
Buffer: Untreated areas placed in immediate proximity to no-spray or sensitive areas to provide a margin of safety by absorbing any drift before it reaches the no-spray sensitive areas.
Herbicide-Free Zone or No Deposition Zone: This area must exhibit no visible effects of herbicide activity. These areas are generally very sensitive (such as riparian areas) or must be protected for one reason or another due to their purpose or usefulness (such as protected wildlife habitat).
Efficacy: The ability to produce the desired result; effectiveness.
Risk Management Provisions for Aerial Herbicide Applications:
(Taken from the Forest Management Herbicide Reference Manual)
Risk is defined as ";chance or possibility of danger, loss, injury or other adverse consequences."; With respect to herbicide use, risk can generally be categorized into two different types:
- Herbicide release: an unauthorized release due to spills, leaking equipment (nozzles/booms) or applications to an area not approved.
- Off target Site Pesticide Excursions: movement of the herbicide
off the approved application site due to airborne particle drift
or movement through the soil.
Through experience and continual development in equipment technology, risk management techniques can be incorporated into spray programs to minimize risk. The following points are things to consider to reduce risk (more detail on these is provided in the Forest Management Herbicide Reference Manual mentioned above). Any or all of these risk mitigation techniques may be part of the application conditions outlined in the range improvement plan.
Aircraft: Fixed wing vs. rotary wing aircraft. Each type has its advantages and disadvantages. For example, if the application area is relatively simple, and is in relatively close proximity to a landing strip, a fixed wing may be the best option. If however, the area is very irregular, has highly sensitive areas adjacent to them; and/or is not close to a landing strip, a helicopter may be the best choice.
Equipment: Tank systems, nozzle and boom configurations, nozzle/boom calibration and other technology such as GPS guidance, drift control agents, etc. all need to be considered for mitigating risk.
Reconnaissance Flights: The pilot';s familiarity with the area, the spray zone, buffers, and no deposition zones (herbicide-free zones) is a definite asset.
Perimeters: Need to consider sensitivity of area perimeters; if particularly sensitive for example, they should be treated first in the morning or last in the evening (when winds and humidity conditions are generally more favourable).
Buffers (adjacent to sensitive areas): Buffers are untreated areas placed in immediate proximity to no-spray or sensitive areas to provide a margin of safety by absorbing any drift before it reaches the no-spray sensitive areas. It is very important that these areas be clearly marked and understood by the pilot.
Area Monitors: Having someone on the ground monitoring the application and relaying information (such as wind, temperature and relative humidity) to the pilot can help with the accuracy and efficiency of the application.
Environmental Factors: Wind is a major factor to be considered during aerial herbicide application. The more wind, the higher the risk. Temperature and Relative Humidity (RH) will also dictate the droplet size that is most effective.
Pilot qualifications: The Alberta Aerial Applicators Association has trained and certified pilots in the proper use and application of registered aerial herbicides. These pilots have been trained to have a clear understanding of the equipment needed and conditions under which registered herbicides can be aerially applied to maximize control of target brush and/or noxious weed species. We recommend these certified pilots be used for aerial application of herbicides on Public Lands. For more information on certified aerial applicators, you can check out the Alberta Aerial Applicators Association website at www.albertaaerialapplicators.com.
For additional information, please contact your nearest Lands Division office to speak with a Range Agrologist or PGR Manager (dial 310-0000 to talk to a RITE operator who will connect you to the closest Lands Division office , or view the Contact Us page.
