Invasive and Exotic Species

2. Selecting Release Sites

The sites that you select to release biocontrol insects should be carefully chosen to meet the primary goal(s) of your program. Consider the following when selecting your site:

• Sites selected to function as future collecting and redistribution sites (field insectaries) should be sufficiently large—ideally greater than 10 acres (4 ha)— safe from disturbance or vandalism, and should be accessible for regular monitoring and collection activities. Also, assess these sites for use as demonstration areas for educational and training purposes.
• Sites intended for long-term insect and vegetation monitoring of control success should be safe from interference by other weed management programs and safe from vandalism. You need a long-term commitment by the landowner to allow your monitoring to proceed for a decade or longer. Consider restricting collection of beetles from these sites in order to track the growth of insect populations.

Visit several prospective release sites. Use the following guidelines and criteria to select a site:

Site factors: An infestation covering a minimum of 1 acre (0.4 ha) in size is recommended, but a larger infestation, such as that shown in Figure 24, is better. Choose a site that is in full sunlight (Galerucella beetles, particularly, prefer full sun). Ideally, select a site that has a moisture gradient: this will allow the beetles to select their preferred moisture levels, and large water fluctuations will not jeopardize the release program. Avoid sites that are highly disturbed, where other weed control methods (mowing/cutting, burning) are planned, or where pesticides are used frequently.

Figure 24. Purple loosestrife infestation (UGA1291024).

Presence of biocontrol agents: Make sure you are aware of and coordinate with other biocontrol activities in your area. If other biocontrol agents are already present at the selected site, move on and choose a different location for release. For example, if you want to establish Nanophyes in a field insectary site, first be sure that Galerucella is not present.

Ownership: The landowner must be willing to permit release and monitoring over several years. When getting permission to use a site, be sure to secure the following: 1) written permission from the landowner or land manager allowing use of the area as a release site, 2) written agreement by the landowner allowing access to the site for monitoring and collection for a period of at least 10 years, and 3) permission to put a permanent location marker at the site.

Establish a permanent location marker: After selecting a site, place a brightly colored marker (wood or metal stake) in the infestation. The stake must be tall—about 6 ft (2 m)—and clearly visible to mark the exact location of the release site. If possible, record the global positioning system (GPS) coordinates of the marker.

Establish a photo point: Photographs taken annually from the same location can effectively illustrate the success of a control program. Refer to Section 6 for detailed instructions on establishing a photo point.

Prepare a map: A map of the infestation is helpful to visually assess the size and distribution of purple loosestrife at the site before biocontrol agents are released. A detailed map and written directions to the release site are essential for others to locate the site: note permanent roads, creeks, rivers, mile markers, etc., on the map and in the directions. If possible, include a legal description and GPS coordinates so that the site can be easily re-located.

Monitor baseline vegetation: It is highly recommended that you assess the amount of purple loosestrife and other vegetation at the release site before releasing the biocontrol agents. Pre-release monitoring provides baseline data, allows meaningful before-and-after comparisons, and will provides important information on the effectiveness of the biocontrol program (see Section 5.2 for information on vegetation monitoring).

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