How to Raise and Release Galerucella Beetles Outdoors for
Controlling Purple Loosestrife in Wisconsin
WDNR’s Wisconsin Purple Loosestrife Bio-Control Program (WPLBCP) will send you
beetles for propagation so you can increase their numbers faster than they can on their own, as well as place them where they are needed most. You do this by ensuring ample food, good living conditions and no predators, and by carefully choosing release sites. Bio-control beetles are still too rare in the state to adequately control purple loosestrife. They are still needed in many more infestations to do the job.
Raising and releasing these beetles is easy and fun. Simply, it includes collecting purple loosestrife roots from your local wetland, potting the plants and growing them in a child's wading pool, adding beetles when plants are two feet tall and dropping the pots off in your local loosestrife patch about a month later. There are a few crucial details laid out here that will help you succeed in propagating your beetles, yet this is also a project whose parts can be accomplished in many ways. You have the freedom to do it as it suits you--as long as you produce lots of healthy and hungry beetles! Please read this guide carefully, then make the process your own by accomplishing the necessary steps in your own way. If you find an effective and unique way of doing so, please share it with us. Check WDNR’s web site annually for updates to this and other appendices.
A Project Timeline: Getting Ready
In order to plan ahead, please consider the following typical outdoor project timeline, starting in the fall (Table A.2.1, Figure A.2.1).
Autumn Winter Spring Summer Summer
Locate and Sew net cages Dig, pot, and Take pots to Photograph site
mark loosestrife cage loosestrife wetland and
Gather tools and materials Set up rearing Release beetles
Dig and store Sew net cages Receive and Record and send release data
roots* add beetles
* Usually only in the North where spring can be very late or cold, slowing the start of
Table A.2.1. Typical seasonal tasks for purple loosestrife biological control.
This timeline for outdoor rearing is based on the biology of the plants and beetles, our temperate climate and your location, and should result in the healthiest beetles. It is,
however, possible to rear beetles indoors, earlier in spring and entirely within the school year; however, early research suggests that beetles produced this way are less successful in establishing outdoors. Even if true, all produced beetles have value, and the additional educational benefits from more student exposure to the whole rearing process may be worth the tradeoff in the long run. More research will be done and, if warranted, a separate indoor rearing appendix will be produced and winter beetles made available.
In the summer before spring rearing, you should become familiar with other wetland plants to be sure you can correctly identify purple loosestrife. In the fall, search your local wetland for the purple loosestrife plants that you want to use and mark them with brightly colored plastic flagging. At that time plant stems and leaves should still be present to help you choose the correct and best plants. If you need to find a site, access GLIFWC’s map web site in Appendix 1 or consult WPLBCP.
North of Wausau, consider digging your plants in the fall after a few hard frosts, rather than in spring when a late thaw could delay digging. An early start for your plants is important for ensuring that they grow enough to receive beetles when they are available. Consider buying a wading pool in fall as well, since they are often unavailable until late in the spring.
Winter is the time to collect needed tools and materials. Appendix 3 lists everything you might need. Some materials may be available free from WPLBCP. This is also the time to sew your netting into sleeve cages since you will need them as soon as you pot your plants. Cage construction is simple, starting with fabric pieces 46+ inches by 78 inches: Fold each piece along the short side to make it 23+ inches by 78 inches (doubled). Sew down the 78 inch open seam, tapering the bottom end of the cage to match the circumference of your pots. Sew each seam again with a zig-zag stitch to strengthen it.
In the spring, dig roots as soon as wetlands thaw and before any shoot growth, typically early April in the South and mid to late April in the North. About four weeks later, usually early to late May, your plants need to be around two feet tall to receive beetles.
In mid summer, about four to eight weeks after adding beetles, you will release your new beetles and send release site information to WPLBCP (Appendix 5.) It is very important to take two photographs of your site several weeks later, when the plants are in fullest bloom, and send one to WPLBCP. The other will give you a record of the early site for comparison with photos from later years to easily see satisfying changes in the site’s vegetation. Further monitoring procedures will be outlined in a future appendix.
Purple loosestrife is a state-listed noxious weed, and, before cultivating the plant, you must send a copy of your signed permission form (Appendix 4) to WPLBCP in order to raise plants legally. The only legal purpose is to produce bio-control insects.
Purple loosestrife is a perennial, with only the aboveground plant parts dying each fall. The aim in growing plants from pre-existing roots is to quickly produce the largest plants with the most foliage possible in order to maximize beetle feeding later in the spring and summer.
Dig roots immediately after your wetland is ice-free. This both prevents damage to tiny
new shoots during transplanting and allows you to set up the best conditions for fast early growth of the transplants. If you have a northern Wisconsin site where roots are often frozen late into spring, consider collecting them the previous fall. You must then store them moist and cool over the winter. This may be done outdoors under a shaded tarp or in a water-filled pool, or indoors under moist burlap at 40 degrees or lower and dark, such as in a root cellar. Always dig more roots than you need because many will not survive until spring. If a late spring is delaying your digging, you can travel to a southern location to get roots. You can locate appropriate sites on GLIFWC’s map web site in Appendix 1 or by consulting WPLBCP.
Starting with large roots is critical, so choose the largest roots that will fit into your pots
to produce the most foliage possible and avoid premature plant death from larval feeding. Gauge the size of a clump by the number of stems from the previous growing season. A clump with 6 to 8 stems is probably large enough, but more stems are better. Treat the clump as a single plant, though it is just as likely to be several.
Choose a wetland with good footing and vehicle access since roots are often heavy. Plants in friable soil, sandy soil or standing water are usually the easiest to dig. Clip the old stems of a clump, leaving a "handle" of 8 inches or so. Use a shovel to cut, or a fork to loosen, around the outer base of the clump and lever the roots out by pulling up with your legs and rocking backwards. A large clump can be pulled or cut apart if it is too heavy to carry or too big for a pot, especially if it is more than one plant. Clip the remaining stem stumps and pull off as much soil, other plant roots, organic matter, and dead loosestrife roots (black and brittle, on the bottom) as possible and leave this material in the wetland. Haul roots out of the wetland and transport them in garbage bags or tubs for ease of carrying and to prevent spreading plant parts or seed-contaminated soil. Wear appropriate boots and clothes, including protective eyewear!
Transplant at least 12 to 15 roots for each 10 growing plants desired. Extra plants will be especially useful for over-wintering captive beetles on-site.
In an empty pool, mix water with your potting soil until it is thoroughly moist. Fill each pot with at least three inches of soil, adding more, if necessary, for the crown of each odd-sized root to be at the same height as the others, and around a couple inches below the top of its pot. Sprinkle in a teaspoon of slow-release fertilizer (if not already in the soil mix) and mix it with the top inch of soil.
In another empty pool or container, spray-wash each root with a garden hose to remove most of the remaining organic material and mud, especially from the root crown, to get rid of any plant or insect predators and their eggs. Transfer waste material from this process back to the original wetland or to a capped landfill to avoid spreading loosestrife.
Place the largest root mass possible into each pot. If necessary, several small roots can be
combined to produce the necessary 6-8 new stems. Clip any jutting root tips to allow packing in more root mass. Pack each pot with soil to within 2 inches of the top, filling all air pockets around the plants' roots. Larvae need to be able to penetrate the soil surface, so do not pack the soil too firmly. Water sparingly at thistime just to help settle the soil surface. Starting with saturated soil reduces the need to water. Hereafter, always water by filling the pool to prevent washing soil and fertilizer into the pool water.
Pool Set-up and Plant Care
Place a net sleeve cage over each potted plant as soon as possible. This protects the plant
from damage and infestation by plant or insect predators. The cage must be securely closed at both ends. Duct tape one end of the cage to the dry pot top, above the water line. (You may use a draw cord or large rubber band over the net at the top of the pot to secure the net, but adding tape will prevent wind from blowing the net off.) Try to leave as much fabric above the tape as possible to give the plant maximum amount of room for growth. Tie the top of the cage closed with a cord or wire, place the pot into a pool and suspend the bag from a support. The net cages must be supported to allow plants to grow unhindered. Many kinds of support systems will work. These range from a thin post, such as conduit, inside of each cage to exterior post systems with suspended cross members. (Interior supports should only be used where wind is minimal since they often allow pots to blow over.) Guy lines can give added stability to any system.
Place pools in full sunlight, but out of strong winds. Arrange pots around the perimeter of a pool to give each plant maximum sunlight. Five to six pots fit around a 4-foot pool with extras in the center and two of these pools are the best option for 100 beetles. They are also easier to transport and offer more versatility in space arrangements. Ten pots also fit around a 5-foot pool with ample center room for extras, but less sunlight may reach each plant than with 4-foot pools. At least one plant in a project should be cage-less to attract any escaped beetles. Other extra plants should be caged as replacements for weak plants.
Always keep several inches of water in pools containing plants. Check pools daily, even on weekends, if the weather is hot and sunny. Drill drain holes several inches up a pool’s sides, if necessary, to ensure that the maximum water level is never higher then 2-3 inches below soil heights, since pupating beetles do poorly in saturated soils.
Mosquito larvae may live in your open-topped pools, an increasing concern because of West Nile Virus. Eliminate them by putting in a few goldfish or native mud minnows, both of which can survive in low oxygen environments. Frogs may appear on their own
and accomplish the same task. You may have to replenish either, however, if you let water levels drop too low or if local predators such as raccoons begin to eliminate them!
Plants need about 4-6 weeks, depending on weather conditions, to grow two feet tall and be large enough for beetle introductions. You may grow them indoors, if possible, to shorten this time, but move them outdoors before adding beetles. Crowns take a week or two after potting to begin to grow, but then grow quickly. When stems are 12 to 15 inches tall, spread the small leaves at the tip of each growing point and carefully pinch it off. This stimulates the growth of lateral stems, provides more foliage and helps keep plants from growing too tall for their cages.
Figure A.2.2. View of pools and possible structure.
2 4’ 1 5’
Raising Your Beetles
When around two feet tall plants are ready for beetles. Let WPLBCP know ahead of time when you expect this to be and we will send your beetles on or soon after that date. (There is a small, tax deductible donation to pay for delivery that should be sent to WPLBCP with your application; Appendix 4.) Placing beetles on plants that are too small, have too few stems or too little foliage can result in reduced beetle production and even premature death of the plant, and require early beetle release.
Beetles will come to you either shipped overnight from Madison or delivered in-person by the WDNR or UW-Extension. Once you receive them, put the beetles into your cages as soon as possible. If you must delay, keep them cool and out of direct sunlight, especially if in the shipping container and the day is hot. If the delay is overnight, open the shipping box and bag inside to give them fresh air. Gently knock the beetles away from the bag opening first since they will be eager to escape. Keep the shipping container, unless instructed to return it.
When you are ready to transfer beetles to your cages use an aspirator or similar device to move 10 healthy beetles to each plant. If there is any reason to suspect spiders or other predators might be on your plants (e.g., your plants were not netted immediately after transplanting), check them over carefully right before adding the beetles. Open the top of
each sleeve cage and simply drop the beetles in. Tightly cinch the tops closed and re-suspend the cages. Avoid using fingers or tweezers to handle the insects. Divide any leftover beetles among your larger plants. As soon as beetles are on your plants it is time to decide where your new beetles will go; do not wait until you see these to decide!
You will see your beetles’ four life stages if you watch carefully over the following 4-8
weeks. Many web sites listed in Appendix 8 have color photos that will aid you to identifying them. Note that temperature and weather conditions are important factors in their activity level and growth rate.
Old Adults that you receive are from the previous year and are dark brown with a black stripe along the edge of each wing cover. They are 4-6 mm in length and about half as wide. They over-wintered at the soil surface or soil litter either in a wetland or surrounding uplands and have recently been collected in the field as they emerged to feed and mate. They will live about 6 weeks after emergence and each female will lay about 10 eggs a day for 30 days. They "skeletonize‖ leaves by chewing many small, fairly round holes in them.
If no adult beetles appear to be present after the first week (also indicated by lack of leaf damage), look inside the cage, especially in the lower parts of the plant and along the soil for live adults and insect predators. Remove or kill any of the latter. If neither is found, check the cage for holes or other possible means of escape. Check your cage-less plant for escapees and return them, once any means of escape has been fixed.
Eggs are tiny (less than 1 mm) and cream colored, with an uneven black line of frass (insect excrement) deposited on them. They are usually laid in bunches, often along the edge of adult feeding damage on both stems and leaves or in leaf axils. Humidity is important for egg hatching so make sure pools always have water in them to keep humidity high. Eggs hatch 2-3 weeks after they are laid. If you see no eggs, but adults are present, you may have a poor mix of beetle species (there are two) or genders. Try mixing with adults from a cage with lots of eggs.
Larvae are very small (about 1 mm.) and hard to see when newly hatched. Larval damage in the shoot tips, called ―tip-feeding, ' should be obvious early on, especially when
accompanied by frass. Larvae are yellow with a dark head capsule and molt five times, ththeach time increasing in size. Over 80% of larval growth occurs in the 4 and 5 larval
instars. Their feeding damage is described as ―window paning‖ because the leaf tissue is left brown, thin, and translucent, unlike the holes left by adults. After 2 to 3 weeks of thfeeding, large 5 instar larvae move to the soil to pupate. If any plant turns completely brown while larvae are still visible, place that plant into the field immediately and check
your other plants daily for the same problem, especially any that are smaller or had many eggs.
Pupae are the transformation stage between larvae and new adults (tenerals). When most larvae seem to have disappeared, they are likely in the top ? in. of soil as pupae. During pupation do not allow the upper layers of soil in your pots to be saturated with water for
very long or many pupae will not survive. Some manage to end up floating in the pool water; carefully retrieve and return them to the soil in a cage. After 2-3 weeks pupae emerge from the soil as teneral adults.
New Adults will emerge from the soil up to 100 times more numerous than the number of old adults started with 6-8 weeks earlier. They are usually light tan with no dark coloration on their wing covers and are easy to tell apart from old adults, with whom there may be a very slight over-lap in time. They collect at the top of each cage trying to disperse, especially on sunny days. Numbers are low at first, but hundreds more may appear every day, so place a pot in the field as soon as any are seen in its cage. Teneral
adults will not survive long if plants have turned brown from larval or other adult feeding. In this case add fresh loosestrife stems (first inserted into florist clips with water) to the cages to feed them for a brief time, but release them as soon as possible.
Releasing Beetles and Follow-up
Release your beetles when the first new adults appear in your net cages, but decide on
suitable release sites much earlier. 10 old adults produce up to 1,000 teneral adults per pot, for a total of 8-10 thousand when you start with 100. This is enough to start 4 or 5 small colonies, since you should put out a minimum of 2,000 beetles (usually 2-4 pots) on a site to start a viable population there. However, the best strategy the first year is often to set up a couple insectories, which are small, high quality sites for producing new local propagation stock within 2-3 years. Such sites have 50+ healthy, mature loosestrife plants, but are ? acre or less in size and are well separated from larger loosestrife infestations. Beetle numbers can build up quickly and stay concentrated on such sites, making it both easy to collect breeding stock as well as see great results! These sites should also have landowner assurance of site security, good access and footing, be free from insecticide spraying (e.g., for mosquito control) for at least a year, have only very short or no summer flooding and be places from which the loosestrife is unlikely to infest new wetlands.
If you wish to try producing your own propagation stock for the next year, for either spring or winter (indoor) rearing, you will need to over-winter captive beetles retained from your first year’s rearing. Instructions for this are in Appendix 7.
After setting up insectory sites the first year, or if no further rearing will take place, you can place beetles on any site where no other controls are practical. For more information on site choice, consult WDNR or UW-Extension personnel, or refer to ―Purple
Loosestrife Control Recommendations‖ in Appendix 6 and other publications, such as the brochure "Purple Loosestrife: What You Should Know, What You Can Do" (available on the web—see Appendix 8). Transport potted plants and cages together. Ensure that beetles arrive in good condition by avoiding jarring (as in the back of a pick-up) and high temperatures. Fold plants and cages over gently if space is small, such as inside a vehicle.
Cluster pots within several meters of each other in a wetland with each pot adjacent to a large, healthy purple loosestrife plant. Remove the cages and shake out any adults onto
nearby foliage. Bend the adjacent loosestrife plant stems into the spent, potted plant stems to allow any remaining larvae and new beetles to walk onto fresh foliage for immediate feeding. Mark either the ends of the site or the individual pot locations with PVC poles so you can find them again. Wait at least 4 weeks after the release before recovering your pots to allow the remaining beetles to emerge and disperse, or leave the pots until the spring.
If your beetle release is late, hundreds of beetles may congregate in your cage tops. If no green plant tissue remains, you must release them immediately or feed them, or they will die, then or later, from the stress of starvation. A different release procedure is recommended to encourage these beetles to stay on the site after release. At the field site loosen the cage bottomfrom a pot, lift the pot and spread open one side of the cage, inserting several healthy field stems into it as you lower it and its pot to the ground. Snug the bottom of the cage around the pot and new stems as well as possible. This gives the new adults additional ―field‖ food, getting them used to the site, before they are actually released. Remove the cages within 2-3 days, but leave the pots as above.
On the day of every release, please fill out and mail in a copy of the Site Location Information form in Appendix 5 for each release site. Return to each release site and take two photographs of it in late summer when the loosestrife flowering there is its most spectacular and send one photo to WPLBCP. This visual record in year 0 can be used to contrast with photographs of, or visits to, the same site in ensuing years to see how much the beetles are affecting the loosestrife. Larvae demolish flower buds and as their numbers build there should be less and less purple on the site at this time. Put a marker on the place you take the picture so later shots can be from the same spot. This is the eaiest way for you to gauge your success with biological control!
New adults feed on leaves for a few weeks, but disappear around mid-August to over-winter in the leaf litter near host plants or in surrounding uplands. They and their feeding damage are often difficult to find then, but look carefully when you return to collect pots or take photographs. Finding beetles is easiest in the spring. Consider visiting your site then, especially as part of optional monitoring procedures (in a later appendix.)
If you have any questions, comments or suggestions about this process or want to send in site or release information and photographs, please write the Wisconsin Purple Loosestrife Bio-control Project at Wisconsin DNR, 1350 Femrite Dr., Monona, WI 53716; firstname.lastname@example.org (e-mail), or call 608-221-6349. Good luck!
Appendix # 3: Materials for Rearing 100 Galerucella Beetles
Note: This is an exhaustive list and you may not need, or need to purchase, all items. Some may be available for free from WPLBCP* or elsewhere (such as pots from landscape businesses or buckets (that need holes drilled) from school lunch programs.
Getting Ready and Collecting Roots
1. Plant ID book (See Appendix 9)
2. Map(s) to location of loosestrife roots and beetle release sites--Use a good local map
after consulting GLIFWC’s web map at www.glifwc-maps.org.
3. Colored flagging in rolls or on a metal stake
4. Filled out, signed, copied and mailed Wisconsin DNR permit letter
5. Shovel and/or fork for digging and cutting roots
6. Plastic tubs (Rubbermaid type) or plastic bags for hauling roots and waste 7. Pruning shears to cut off old dead stem tops and root tips, if necessary 8. Gloves and eye protection, rubber boots and old clothes
9. 12 to 15 BIG purple loosestrife roots from a local wetland
10. *12 to 15 plastic pots, 10 to 14 inches in diameter
11. *About 2.5 cubic feet of high peat content potting soil (Fafard or a similar mix) 12. *1 pound of fertilizer, slow release type like Osmocote 18-6-12, unless in the soil 13. Hose and water source for rinsing roots, wetting soil and filling pools 14. *Two 4-foot child's pools or one 5-foot pool, or other suitable containers
Pool set-up and Plant Care
15. *24 yards of 48+ inch wide, no-see-um insect netting, thread and sewing machine to
make 11 net sleeve cages about 78 inches long. Fold each piece of fabric along its
short side and sew down the open 78-inch seam, tapering the cage at one end to
match the diameter of your pots.
16. *Duct tape (and perhaps bungi type cords) to attach cages firmly to pots 17. Wire or string to tie cage tops shut and to supports; also for guy wires 18. 4' by 8' of space in full sun or at south facing windows
19. 7 foot high cage support system for suspending net cages—clotheslines or conduit
posts or a design of your own!
20. Dependable watering system
Raising your beetles
21. *100+ over-wintered beetles from WPLBCP, field collected or from other suppliers 22. *Aspirator for catching and moving beetles.
Releasing Beetles and Follow-up
23. Heavy duty transportation for taking potted plants into the field. 24. Site release form (filled out and mailed to WPLBCP on the day of release) 25. 3 to 11 PVC posts--for marking release site and photo point
26. Camera and film
Some Outlets for Hard to Find Materials and Videos
Beetles for rearing (or field release in July-August): (Call for details)
; Cornell University, 607-275-3786 (from New York State - minimum # to order)
; Beetles Unlimited, 608-831-5601 (from Wisconsin – no minimums)
Insect Netting: (need~78in. of fabric/cage) (WPLBCP supplies free w/3 year rearing)
Venture Textiles 56in.White or slate; 500 yd. bolt $1.10/yd.;
115 Messina Drive lesser yardage is $1.10/yard plus $10 cut chg
Baintree, MA 02185
Madison Area Seamstress: (in case you can't sew sleeves yourself) Sleeves made with your fabric -- $6 (no drawstrings), $10 with 1 drawstring, $12 with 2 drawstrings. Prices may change without notice. Call for details.