Garlic Mustard Management Protocol
Aldo Leopold Foundation
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Introduction
Since 1996, garlic mustard control on Aldo Leopold Foundation property has consumed a great deal of staff time and foundation resources. Beginning in 2004, a systematic approach to mapping and treating populations has been implemented and continued to evolve in response to field experience.
This step-by-step guide is intended as an introduction and guide to ALF’s approach to garlic mustard control. Here, we provide the basic steps for fieldwork and data sheets for your use in garlic mustard control on your own property.
While the main activities are described separately, often a few are occurring simultaneously—while one person is monitoring, a crew of two or three may be out chemically treating an area.
We have created a field data sheet to record pertinent information about each individual patch of garlic mustard. This record helps us track the movement of populations over time and helps monitor the success of our control efforts. We have also created a Daily Action Data Sheet specifically for the garlic mustard program. This sheet provides one place to record all action taken during garlic mustard control. If updated daily, it will greatly simplify the process of recording and reporting how much time and herbicide went into garlic mustard control for each management unit.
Scouting
In areas densely populated with garlic mustard, most new populations are discovered within the process of monitoring, treatment, and revisits. However, in less densely-populated areas, time must be devoted to scouting in order to find new populations. Populations discovered during scouting will be mapped according to the mapping protocol. Treating outlying and remote populations is the critical first step in controlling the spread of GM on your land.
Identify an area that needs to be scouted before monitoring and treatment can begin. Prepare maps for use in the field (may include known garlic mustard populations, trails, natural features, and vegetation types).
Necessary materials include: a GPS unit with fresh (and spare) batteries, fluorescent irrigation flags, a wide-tip permanent marker, and a clipboard with maps, data sheets, and pens. A compass is also useful for navigation. Minimum crew size is two, though three to four is optimal.
Select an area with easily-defined boundaries, such as a road, trail, or natural terrain or vegetation changes. At the edge of your scouting area, begin walking transects. (In areas with featureless terrain, it is important to follow a compass bearing to be certain the entire area is thoroughly searched.) Crew members walk 5 to 30 feet apart, depending on the density of the shrub and herbaceous layer. When a new populations is found, follow mapping protocol below.
Mapping
Mapping—recording the location of newly discovered or newly established populations—is fundamental to garlic mustard control. Mapping is conducted primarily during scouting and monitoring efforts, but be prepared to map new populations during treatment and revisit efforts as well.
Each patch is flagged with a bright orange irrigation flag, numbered, and mapped using a GPS unit. The number on the flag corresponds with the point ID number entered on the GPS unit. The waypoints are downloaded into an ESRI GIS program, and the waypoints can be displayed on a map of your property using air photos, topographic maps, or topographic maps overlaying air photos. Given the resolution of the air photos and the accuracy of the GPS waypoints, it is relatively easy to use computer-generated maps in the field to re-locate mapped populations for treatment throughout the season and year after year.
Before going into the field, determine the last identification number assigned during the previous year. Make maps showing known locations. Depending on the size of the property you are managing you may want to break your land into smaller management units (these may also correspond to other management practices, such as prescribed burn units, timber management units, or other invasive species control units).
In the field
Necessary materials include: a GPS unit with fresh batteries, irrigation flags, a marker, and a clipboard with maps, data sheets, and pens.
Identify a new garlic mustard population. When an apparently new, unflagged population is discovered in the vicinity of existing populations, consult the field data sheet (column two records the population’s maximum diameter in the past) to determine if the population of interest falls within the radius of an existing population or not. If not, the population must be mapped and flagged as a new population. Using the GPS, mark a waypoint at the site. If necessary, type in the correct identification number for the new population before saving the point.
Estimate the population’s diameter (a measuring device is useful in this estimation – we use a 6’ piece of PVC pipe marked off in 1’ increments and we find the hollow tube is also useful for carrying extra flags!). In irregularly shaped patches, diameter should be to the farthest extent. Place an irrigation flag in at the center of the population. On the flag, record the number assigned to the plot (It may be useful to record the diameter of the patch in smaller print on the flag as well for future reference in monitoring). For some populations, the edge of the patch may not be obvious—for very large populations, irregularly shaped populations, or those occurring in dense brush. To identify the entire patch for chemical treatment and revisit crews, it may be useful to use smaller or other colored flags to mark the edges of the patch.
Monitoring
Monitoring may be useful for tracking how garlic mustard populations change over time. Monitoring can be completed by one person. Sometimes it is more efficient to have a two person crew: one devoted to collecting data and another to mapping new populations and re-flagging existing populations. Generally, monitoring is conducted by a crew member who has past experience with treatment.
Data recorded during initial monitoring includes: diameter of population; density; age of plants present; number of dead stems present; treatment method used during initial attack.
Using the field data sheet
Letters on the field data sheet are to be circled to describe the population according to the following quantifications:
Shape: Because not all of the populations are perfect circles we have considered the “diameter” to equal the longest axis of the population. This may cause some confusion in the field. Populations can be very linear in shape, which means the recorded diameter—the longest axis—is very large compared to the width of the population. Knowing the shape of the population can help you relocate it and can help in quantifying what the diameters mean.
- Elongate: Very long and narrow patch (length is 4x or more width)
- Oval: Patch is larger in one direction than the other (length is 2x to 3x width)
- Round: Diameter of patch can be accurately measured (length is roughly equal to width)
Density: Populations are described according to four categories, from dense clusters of plants to groups that are very spread out.
- One: one plant present in patch.
- Dense: 80 % of the ground is covered by garlic mustard, and the majority of garlic mustard plants are touching each other on at least three sides.
- Scattered: 60 % of the ground is covered by garlic mustard, and the majority of plants are touching two other plants.
- Very Scattered: 40 % of the ground is covered by garlic mustard, and the majority of plants are touching only one other plant.
- Isolated: 20 % or less of the ground is covered by garlic mustard, and the majority of plants are not touching one another.
Age: Garlic mustard is a biennial, so there may be first year (non-flowering) plants, second year (mature) plants or both. Knowing which was present at the time of monitoring is helpful in understanding the lifetime of the plot. Number of dead stems helps understand the lifetime of the plot and the success of last year’s efforts.
- Adult: second year plants with flowering stalk.
- Seeding: first year plants that have just sprouted or are a basal rosette of leaves.
- Both: both first and second year plants present.
Treatment: What control method was applied. We only use chemical, hand-pulling, or both, but if you are also controlling using other methods (weed torch, etc.) you should include them in your list.
Treatment
Spraying garlic mustard with glyphosate herbicide is a very efficient way to control GM populations in larger management units. Using mechanical means alone (that is, pulling by hand) is possible in smaller areas, but is time prohibitive in larger areas. Ideally, spraying happens after scouting, monitoring, and mapping is completed for a given management unit.
We use a 1.5-2% glyphosate mix. Consult the guide included with the chemical to determine how much concentrated chemical to mix with water. We add a tracer dye to see which plants have been sprayed in the field.
Suggested personal protective equipment (PPE) includes: goggles, boots, gloves and coveralls. It may be necessary to purchase new pairs of chemical-proof gloves before the beginning of the season. Ideally, each crew member will have a map during spraying efforts; this makes it easier to navigate and to cross off populations as they are visited.
Backpack sprayers are pressurized with a hand pump. Keep the pressure high enough that the herbicide comes out as a fine mist. Plants should be covered with enough spray that the leaves are covered, but not with so much spray that the herbicide forms droplets and rolls off.
Re-Visits
Following the completion of all chemical treatment, each known population must be revisited. Any plant that was not killed by the herbicide must be pulled, and, depending on the viability of the seeds, bagged and removed from the site. Re-visiting each site also provides one more opportunity to find garlic mustard populations that remain undiscovered. Revisits should be marked and checked off on field data sheets.
Starting late June (in our region), seed pods become brittle and shatter. At this time, re-visits are no longer practical, since relatively little of the seed is being removed from the area.
Fall Treatment
Application of herbicide in the fall is a highly effective way to treat garlic mustard in areas with high native diversity in the understory. After mid-October, most native flora is dormant, while garlic mustard basal rosettes remain green. As long as the temperature is above freezing, plants are actively photosynthesizing and water-based glyphosate is effective.