Invasive and Exotic Species

4. Handling and Releasing Purple Loosestrife Biocontrol Agents

How the insects are handled and transported after they are reared or collected will affect whether they survive at the new site. This section includes guidelines for handling, shipping, and releasing biocontrol agents.

4.1 Handling purple loosestrife biocontrol agents

Transportation. To minimize stress and harm to beetles, transport and release them as soon as possible (preferably within 24 hours). Ensure insects have plenty of fresh food at all times. Keep containers cool and dry during transportation. Put the containers in a cooler with ice packs secured to the bottom or sides of the cooler. Cover the ice packs with newspaper to prevent direct cold and condensation from contacting the containers. Adult beetles can survive a few days in a refrigerator if necessary, but keep storage time to a minimum.

4.2 Shipping purple loosestrife biocontrol agents

To ship biocontrol agents, plan the route and timing of shipments to prevent undue delays and stress on the insects. Collect the insects early in the week and ship right away by overnight courier (for example, FedEx, UPS, or DHL) to be sure they arrive before the weekend. Instruct your cooperator(s) to release the insects immediately upon receipt. Observe the following general guidelines:

Know the regulations: It is important to know the regulations pertaining to shipping biocontrol agents across county or state borders. Interstate transportation permits may be required. To learn the current regulations, contact your local cooperative weed management area, state department of agriculture, or the USDA Animal and Plant Health Inspection Service–Plant Protection and Quarantine office (USDA-APHIS-PPQ) (http://www.aphis.usda.gov/ppq).

Prepare the insects: Prepare the insects right before the scheduled shipment to minimize stress. Follow these steps:

• Separate beetles from all other unwanted material, such as other insects,spiders, weed seeds, etc.
• Put the beetles in breathable or vented shipping containers (described above).
• Pack the containers in an insulated shipping box (Figure 33) with a frozenice pack well secured to the inside. Seal each frozen ice pack in a plastic freezer bag to prevent condensation inside the box as the ice pack melts.

Figure 33. Shipping box for purple loosestrife beetles. (UGA1291033)

4.3 Releasing purple loosestrife biocontrol agents

There are many factors that can determine whether insects establish and flourish at a release site. Few of these are under control by humans (weather, wildfire, etc.), but follow these general steps for releasing biocontrol agents to give the insects the best start possible:

Timing the release: Release the beetles at the appropriate growth stage of purple loosestrife. For example, when releasing Nanophyes, purple loosestrife should be at or near the flowering stage. If most plants are beyond the flowering stage, it is too late to release at that site. Locate a different infestation, perhaps at a higher elevation, that is at the flowering stage.

Number of biocontrol agents to release per site: The number of insects to release per site depends on; 1) the insect species, 2) resources available to collect, 3) the time of year.

• For Galerucella: it is possible to collect large numbers of beetles (several thousand), thus a release of 1,000 beetles is possible. But even releases of 200 adults in the spring have yielded good results. When collecting from the summer generation, a minimum release of 2,000 Galerucella is recommended.
• For Nanophyes: at high densities, it is possible to collect several hundred beetles in an hour. A minimum release of 200 adults per site is recommended.
• For Hylobius: it is more difficult and labor intensive (or expensive) to obtain Hylobius, but a release of at least 100 beetles is recommended.

Release of biocontrol agents: Release insects as soon as possible after you receive them; do not wait for good weather (but avoid heavy downpours). Release in the early morning hours between 6 and 10 a.m. or in the cooler evening hours between 6 and 10 p.m.; biocontrol agents are less likely to scatter if released at cooler times of the day. In general, you can release insects either in cages or make open releases. Caged releases prevent immediate dispersal of insects but require you to put up and take down equipment.

For open releases, get to the desired release location, open shipment containers, and gently shake all insects, purple loosestrife stems, and florist foam at the base of a vigorously growing purple loosestrife plant. Do not release over water, but at the shore or on dry land if possible. Release all the insects at once at a single location; do not disperse them at the site, as insects will naturally disperse on their own.

For caged releases, place a mesh or organdy bag over a plant (Figure 34), release insects into the caged plant, and tie the bottom of the bag to the stem. Cages confine the insects for a period of time so they adjust to the site and easily find one another, but cages need to be removed within a few days.

Frequency of release: Often, a single release will be sufficient to establish an insect population, but more than one release may be necessary if previous releases failed. Do not get discouraged, and bear in mind that it could take two or more years to determine if the agent released (especially Hylobius) successfully established.

Releasing multiple species of agents: As a rule, release only one biocontrol agent if you plan to establish a field collection site. Locate release sites at least 2 miles (3 km). apart. At other sites, you can freely mix (UGA1291034) species to assess how control is influenced by different insect combinations. Be aware that insects will migrate and establish new populations over time. Place the permanent location marker: Place the marker at the location of the insect release. This location will be later used to relocate the site and for monitoring activities.

Figure 34. Releasing Nanophyes marmoratus on caged purple loosestrife.(UGA1291034)

Take photos: Take a series of photographs to record the release (see Section 6).

Fill out and submit a release form: Complete the Purple Loosestrife Biocontrol Release Form (see Appendix). Submit the form to your county weed superintendent, cooperative weed management area, or university or state biocontrol expert. Keep a copy for your records.

Summary: Handling and Releasing Purple Loosestrife Biocontrol Agents

• Use sturdy, breathable containers with food according to instructions.
• Sort insects before packaging them to ensure that predators (e.g., spiders) or weed seeds are not trapped inside the containers.
• Avoid physical damage to the biocontrol agents by taping down ice packs.
• Keep insects cool during transportation.
• If release or shipping is not immediate, store the insects in refrigerators no colder than 40 to 50º F (4 to 10ºC) for no longer than three days, or keep them in an ice chest until they are ready to be shipped or transported.
• Release during the cool times of the day; do not wait for good weather
• Take photos; fill out the Purple Loosestrife Biocontrol Release Form (see Appendix).

[ Contents ]     [ Previous ]     [ Next ]     [ Home ]