Galerucella beetles have a fairly simple life cycle. The adult beetles begin emerging from hibernation by May, feeding voraciously on the newly-emerging leaves of purple loosestrife plants. Eggs are laid in sets of ten, from May to early June, and take up to two weeks to hatch. The eggs often have a distinctive line of frass, or beetle excrement, on each egg after being laid.
Galerucella eggs on a loosestrife leaf.
Once they hatch, the larvae crawl to the tips of the plants to hide from predators and feed on the plant buds (thus preventing flowering). They will go through 3 molts, or “instars”, as larvae, with the third instar causing the most damage to loosestrife through its “window pane” feeding. It consumes everything but the thin cuticle of the plant. We had a few cages where all the leaves were consumed, leaving nothing but crispy brown cuticles hanging from the loosestrife stalks.
Early damage to the top of a loosestrife plant from Galerucella larvae
After feeding for 2-3 weeks, the larvae will crawl down to the soil in your pots (or ground soil, if they are in the wild) and pupate, emerging after 2-3 weeks as pale new beetles. These beetles will want to eat right away, so putting your pots out into the wild once you see new beetles will help ensure their survival.
A released Galerucella in its new home!
Biological Control of Purple Loosestrife: A Guide for Rearing Leaf-feeding Beetles, University of Minnesota:
Galerucella rearing guide, Rachel Carson National Wildlife Refuge:
We had our second beetle release today, putting the beetles out in a heavily infested wetland and along a ditch-line along a major highway. These cages had quite a few more beetles that had emerged from pupae; the release wasn’t expected to happen until next week! So many beetles had emerged and there was so little plant material left in the cages that we decided to move the release up a week.
On the left, a stringy plant that had beetles raised on it, near healthy loosetrife
The wetland we released beetles in was hugely infested with purple loosestrife (and morrow’s honeysuckle, and tree of heaven, and japanese knotweed, and teasel, and crown vetch), and if we can get a good beetle population established here within the next few years, we could protect a lot of critical habitat. This wetland drains directly into the Buckhannon river, meaning it is currently an excellent seed source for spreading invasive plants. Getting even one plant here under control would be a major step toward a healthier habitat.
Keith Krantz of Appalachian Invasives Management (AIM), pointing out where he placed one of the pots containing beetles
The ditches we set beetles in had large, linear populations of loosestrife. We are hoping that the beetles will spread out along the continuous line of food, chowing down over the whole ditch line if possible!
The loosestrife infestation in a wetland where beetles were released. Let’s hope it doesn’t look this healthy in a few years!
These releases have been very gratifying, a culmination of a lot of effort to get these little beetles out into the world to do a big job. We will monitor them over the next few years to see how they establish, and will hopefully raise more beetles in years to come to bolster the populations and increase the efficacy of our project!
Today we had our first release of Galerucella beetles. They had begun to emerge from pupae in several cages, and quite a few of those cages had very little foliage left from the active larvae. A field release was in order, and our chosen location was Elkins Iron and Metal, a metal recycling yard.
It is adjacent to a large wetland that has a fair-sized infestation of purple loosestrife. It has been treated several years in a row by a contractor (Appalachian Invasive Management), with good results every year. However, the hazards of the area (large amounts of metal in precarious piles surrounding loosestrife) have made biocontrol an appealing option to replace spraying as the control method for purple loosestrife.
You can see the damage done by the reared beetles (bottom) versus the healthy purple loosestrife in the field (top)
Despite the annual treatment this location has received, the seed bed of purple loosestrife is pervasive (for at least seven years), meaning that each annual treatment creates an open canopy for more sunlight to get to the seed bed, resulting in germination. The loosestrife infestation is not wall-to-wall like the Triangle Wetland was in 2001, but it is substantial enough that it could support a beetle population. We released 9 cages of beetles at two different ends of the wetland; approximating at least 100 beetles per cage (once they all emerge from pupation), that is a pretty substantial release!
We took the sleeve cages off of each pot and gently brushed the beetles on the cages onto adjacent healthy plants. We also broke stems from the healthy plants to touch the plants in pots we put out, to create a bridge for the beetles to journey upon to find their new homes.
A Galerucella beetle on its new home.
We will leave the pots in the field until late August, then likely collect them in order to prevent litter and to re-use them for next year. The beetles can take as little as 3 years to start thoroughly controlling the loosestrife, but may take up to 10 years depending on infestation size, weather, beetle life-cycle logistics, etc. We will not be spraying the property where the beetles are released, in the hopes that the loosestrife will have a hardy enough population to allow the beetles to establish.
Galerucella beetles can be purchased from growers in several locations, but can also be collected from previous release sites that have an established population of beetles. We are fortunate enough to have just such a site 20 miles from our rearing location, at a wetland near Buckhannon, West Virginia. This wetland had an initial beetle release 10 years ago, orchestrated by the West Virginia Department of Agriculture (WVDA). I was fortunate enough to be invited to come along with David Dick and Laura Miller of the WVDA to collect beetles with them.
Laura Miller, WVDA Taxonomic Entomologist/Museum Curator
We brought sweep nets and small containers to hold the beetles, as well as a cooler with ice and towels for the beetles to chill out in on the way home. We also brought some sturdy boots to traverse the wetland.
David Dick, WVDA Agricultural Weed Specialist
To collect the beetles, sweep the nets in an upward motion along the loosestrife plants, or bend the plants into the net and tap them. Galerucella beetles will fall off of a plant that is disturbed, making them easy to collect. Once your net is fairly full of bugs, you can aspirate Galerucella beetles into holding containers. Make sure you only collect Galerucella beetles in your holding containers, especially avoiding collecting any spiders (who would gladly feast on the beetles!). An aspirator can be purchased or constructed prior to your day in the field. Here are some instructions on making your own:
Using a sweep net to collect beetles from the Triangle Wetland
If you are transporting the beetles a long distance and keeping them in the containers for more than a few hours, the containers should have a way to get fresh air into them, such as a mesh top. If not, an enclosed container such as a film canister or other small lidded container will work fine, as long as it has some loosestrife material in it for the beetles to munch on while they are transported. Keep your insects in the cooler on your way to your rearing site, and you can either place the containers in the sleeve cages when you arrive or tip the beetles out onto the plants, where they can begin happily feeding on their new home.
Triangle Wetland, 2001
Laura Miller spearheaded orchestrating and monitoring a Galerucella release in 2001. At that point there were practically no cattails in this wetland, which is unusual since they are such strong competitors for space. The purple loosestrife was a near monoculture that almost completely obscured the pvc poles put up to mark plots for monitoring. Now, ten years later, it is a challenge to find purple loosestrife in this wetland. It is still there, but the population is considerably smaller, nowhere near a monoculture now. Cattails, willows and other wetland plants are in abundance, and are in fact growing alongside purple loosestrife.
Triangle Wetland, 2010
Laura mentioned how hard it was to walk through the woody loosestrife stems to collect beetles in previous years, and was amazed at how easy it was to navigate the wetland now that the beetles had really gotten a handle on the purple loosestrife population. This is a textbook example of a biocontrol agent doing exactly what is expected. Biocontrols will get a population down to a manageable size, but will almost never eradicate it. The population can then either be left alone and efforts focused on more pressing infestations, or be taken care of much more efficiently and effectively with a much smaller effort. As long as a biocontrol agent is thoroughly and properly studied before a release to ensure no side-effects, biological control can be an excellent tool for invasive species management.
We allowed the crowns to grow for a few weeks before adding the sleeve cages. We used tomato cages to support the sleeve cages, which were made of no-see-um netting to prevent beetle escape and to prevent entry of any predatory insects or arachnids. The sleeves were sewn with a loop at the top to make them able to house a draw-string, and a seam down the side. No-see-um netting is much easier to sew in a regular sewing machine than mosquito netting, since its holes are so small the netting functions much like fabric. Make sure you do not get netting treated with an insecticide; it could cause serious problems with your beetles. We left one pot uncovered per kiddie pool to attract any beetles that might escape so they can be put back into the cages.
The sleeves were cut to have a 1.5 meter circumference; make sure you measure your pots and ensure that the sleeves will be a little baggy to accommodate for the loosestrife plants. We did not end up needing the drawstring loop, but it does provide a nice stiff lip to tie up, supporting the excess fabric at the top. The sleeve cages are approximately 4 feet tall; they are about the right height, but the tomato cages we used to support the sleeves could have been a little taller. The loosestrife grows so fast that some plants are pushing up against the netting at the top. It hasn’t deterred the beetles or the larvae from chowing down on the tops of the plants, so it won’t ruin your project to have cages that are a little short. To close the cages we simply tied a thin strip of netting around the top; it allows you to re-open the cages if needed (for photo-ops!), but holds them tightly closed.
To seal the bottom, the cages can be taped to the pots. We found that Gorilla tape, or some other high-strength tape works best, as duct tape tends to lose its stickiness in rain. We ended up having to tie rubber bands around the bottom of the pots as well as the tape, to prevent escapes. Due to the incredibly rainy spring we’ve had, some netting that came un-taped (thus prompting the installation of the rubber bands), but the merit of an uncovered plant became apparent when a few escapees were easily found and re-caged.
Some protocols for rearing Galerucella beetles call for clothesline to hold up the cages in a strong wind. The use of tomato cages and the ability to set the plants up in an area that is protected on two sides by a building has rendered that unnecessary for our project, but you may want to look into something to support your sleeve cages if you have your pots in an open or windy area.
After receiving permission from the West Virginia Department of Agriculture, we were able to go dig up purple loosestrife root crowns. Purple loosestrife is a perennial plant that grows from a baseball-sized root mass every year. These root crowns can be dug up and repotted to grow plants for your Galerucella rearing projects. We dug up the crowns from lands where we already had agreements in place, so as to not trespass or remove property from a place where we did not have permission to do so. The digging was easiest with a round shovel with a pointed tip; a narrower shovel or one without a pointed tip would make the crowns harder to slice apart or lever out of the mud we found them in.
A potted root crown, with the stalks from last year’s growth visible.
To pot purple loosestrife root crowns, you will need a sufficient number of 3 or 5 gallon pots, a sufficient amount of soil (we used around 3 cubic yards for 24 pots), kiddie pools (each of ours could hold 12 pots), a shovel, plastic bags, and gloves (optional).
The root crowns were sliced out of the muddy soil using a pointed-tip shovel, then levered out onto the ground. The crowns were separated to get individual plants, then the previous year’s woody growth was removed with shears. The crowns were bagged in plastic and then put in pots for transport in a closed vehicle. It is important to only remove material from the crowns at the location you dig them up; if you remove the woody stalks or mud elsewhere, you run the risk of creating a new infestation by spreading seeds. Leave any material removed from the crowns at the site you dig them up.
The crowns were potted in 3 gallon pots in a potting soil with fertilizer already mixed in. We dumped the soil into a kiddie pool, moistened it with water, and potted the crowns, covering them with sufficient soil. The pots were then stood up in the pools, and the pools filled 1/3 of the way with water. The crowns will not need to be watered from the top if the pools are kept filled with sufficient water. Poking holes around ½ way up the sides of your kiddie pools will prevent overflow of the water from rain events.
Loosestrife pots in their pool.
Loosestrife grows fairly quickly, even after the rough handling of digging up the root crowns and re-potting them. To get a bushier loosestrife plant, and so more food for your beetles, you can pinch the tops of the plants off once they reach 12 inches tall. This removes what is called the ‘apical meristem’, or the main upward-growing part of the plant (also the main flowering part of the plant, later in the growing season). This means the plant has lost its ‘apical dominance’, and so the side branches of the plant will start to grow so the plant can still flower.
Side branches growing after the apical meristem has been pinched off.
Loosestrife is fairly easy to grow, and as long as you have a sharp shovel, sturdy boots and permission, it is fairly easy to get out of the field.
Even if you design and build the most beautiful biocontrol setup to raise the healthiest beetles with the biggest appetites for purple loosestrife and are all set to unleash your beetles to wreak havoc on the purple loosestrife all around you, your efforts will be in vain if you don’t have the appropriate permission to do your project. It is illegal in quite a few states to translocate invasive species and the design of a beetle rearing project definitely involves moving an invasive species out of and putting it back in to the field. No matter your good intentions, breaking the law will add several layers of complications that you don’t need for your beetle project.
On top of the legality of moving the plants, moving and releasing the beetles will often require permission as well. For our project, we were able to request and obtain a permit from the West Virginia Department of Agriculture to take purple loosestrife root crowns from an infested site, pot them, and rear beetles collected from a former release site, eventually releasing the new beetle generation into other known infestations of purple loosestrife. It was a simple process that merely required we tell them where we collected the species (both plants and beetles), and ensure we record via GPS and photograph where we released the beetles. It is usually best to incorporate some long-term monitoring of release sites as well, even if it’s just an annual visit to see how your beetle population is faring.
We have also obtained permission for where the beetles will be released to do invasive species removal work. You could run into issues with trespassing and some very confused and unhappy landowners if you don’t explain a project beforehand; it would be odd for anyone to show up with a lot of insects and release them on your property without telling you about it beforehand. I have encountered very, very few landowners who are not perfectly happy to have a free service of invasive removal, as long as they are told beforehand. Receiving permission to do the releases is also important because it will alert people who might have sprayed their loosestrife after you set out your beetles; all your hard work could go down the drain without good communication.
A simple outreach effort can create strong relationships with the community and unite people against invasive species, and a poor outreach effort can result in a long uphill climb back to good standing within your community. Having the support of your community is always worthwhile!