Thank you for reading about our adventures in Galerucella rearing. It has been a great learning experience, and will hopefully provide West Virginia with needed assistance in combating purple loosestrife infestations!
Keep an eye out for later Beetle Blogs, as we hope to do this project annually for a few more years, to bulk up the beetle populations and reinforce our control efforts. Also keep an eye out for local efforts to combat invasive species in general, as every little bit of help counts!
You may or may not have heard the term “Integrated Pest Management” (IPM) lately. It’s a newer approach to invasive species management that uses a multi-pronged approach to controlling infestations, instead of relying on one method for all infestations. It’s an attempt to move away from too much wholesale herbicide application and move toward using an appropriate action for whatever the problem may be. It is also an attempt to increase the efficiency of pest management, ensuring actions taken are effective and meet the goals of your organization or agency.
IPM is a decision-making process more than a treatment recommendation (although treatment recommendations are part of the process). It involves the following:
Set an action threshold:
How bad does the infestation need to be before you take action? The answer could easily be “A single plant.” but could also be “Only plants near or in these priority areas” or “When the infestation approaches this size”. It could be “when the infestation becomes an economic burden”, or “when the infestation approaches my property”. Determining when you should take action against the species is a good first step toward having an efficient pest management strategy.
Monitor and Identify Pests:
You’ve determined when you’re going to take action, now you need to determine where action should be taken. This could be as simple as keeping an eye on your fencerow every few weeks, or as complicated as monitoring hundreds of acres regularly for several species. This step will also determine what pests are likely to be problematic; you may have no Japanese knotweed on your radar at all, so sending a crew out to spray for Japanese knotweed would be a needless expense.
Before you start a treatment, you may be able to take preventative measures to keep infestations from entering your lands. This can include rotating crops, using rootstocks free from pests, ensuring the lands you’re interested in are not disturbed, or reaching out to people about cleaning their gear and clothing after recreating in or near invasive species. All this early effort, which isn’t especially expensive or laborious, can save you time and energy spent on removing invasive species in the future.
You’ve determined your action threshold, have found an infestation that exceeds your action threshold, and preventative measures have failed. Now, you need to determine the most effective control method. This is where using manual, mechanical, chemical and biological controls, either in concert or separately, comes into play. To make the appropriate decision, you use the least risky, but also most effective, control method available. This might be a mechanical control, say for Autumn olive, but using mechanical control for Japanese knotweed or purple loosestrife may be inefficient, expensive and difficult.
It is sometimes recommended to use the least risky control first, and then move on to targeted chemical spraying. However, widespread research can often tell you what size or severity of infestation will require herbicide, so using that information in conjunction with weighing the risks can save time in your decision-making process.
The last resort of any control should be broadcast spraying; avoiding broadcast spraying until all other methods have been tried is recommended.
Our beetle releases are part of an integrated pest management plan; the sites we released them at were above our action threshold, and were highly risky to treat with pesticides. The beetle populations will reduce the risk of contamination of water or injury to our spray contractor, even though they will take more time to control the loosestrife. In other locations, we have decided to use targeted herbicide application, as the sites are accessible and mechanical removal is not viable. In other locations, we have not taken action because our action threshold has not been met (either the location is not as high a priority, or the population is too small).
Careful decision-making in invasive plant management can reap you the rewards of less risk, less expense and more effective control than jumping into a project head-first.
Galerucella spp. Are not the only biological controls approved for release in the U.S. There are also two weevils approved as biocontrol agents, both of which attack different parts of the plant. One weevil’s larvae consume the roots of the loosestrife, and one species attacks the buds specifically, resulting in a distinct reduction of seed production. All of the biocontrol agents take time to establish, but they all have different advantages in different types of loosestrife infestation and so can pick up the slack where another biocontrol species might not do as well.
Hylobius transversovittatus, a nocturnal weevil that feeds on purple loosestrife and attacks its root systems. It can survive in a variety of environments, and can withstand periodic flooding as well. These weevils overwinter as adults, just like the Galerucella beetles, and the adults consume the leaves and stems of the loosestrife. As with Galerucella beetles, the true damage from Hylobius comes from the larvae, who feed on the roots of the loosestrife for up to several years, also using the roots to pupate (pupation can also last several years). Hylobius larvae can affect shoot growth, seed output and plant biomass, but it can take several years for larval root feeding to have a large impact on an established infestation of loosestrife.
This weevil is native to Europe, and was introduced to test sites in Virginia, starting in 1992. Establishment can take up to 6 years, and control can be spotty with this weevil, but it is a common purple loosestrife predator in its native habitat, and can survive a significant amount of flooding (though not permanent flooding) as well, making it a durable biological control agent.
Hylobius is a dark brown weevil with tufts of white hair running down its bag in two lines. It has a proboscis, reddish legs and is a little under a half-inch long.
Nanophyes marmoratus is another weevil that overwinters as an adult and emerges as purple loosestrife begins to grow. They feed on flower buds and lay their eggs in the tips of flower buds. Larvae consume the flowers, pupate in the buds and emerge in August of the same year. The emerged adults feed on the leaves of the loosestrife plant and hibernate once winter sets in. The seed output of purple loosestrife is significantly reduced, as each infested bud does not produce any seeds.
Nanophyes was released in several parts of Oregon in 1994, and seems to be most effective in areas with low plant density; Galerucella are less effective in less-dense loosestrife patches, so Nanophyes is often released in those sites. The research on Nanophyes effects on loosestrife populations is not as abundant as the research on Galerucella beetles, largely because Nanophyes takes more time to establish and spreads less rapidly than Galerucella does.
Nanophyes are very, very small, only 2-3 mm in length. They have a long snout, are reddish-brown and have light-colored markings on their back.
Releasing multiple types of biocontrol agents can result in competition between the agents, so choosing the right agent for your site is a sensible approach to using biological control. Our sites were very rarely flooded, and had high densities, so Galerucella made sense for a release agent. However, your needs may be met through another biocontrol agent, so research into what has been used in areas that are similar to your infested site is worth your time.
It is an integral part of every Galerucella release to monitor, at least annually, the impacts your project is having on the loosestrife populations. Monitoring can involve a simple visual observation, or a more rigorous, plot-based setup to determine the impacts of your released Galerucella beetles.
Regardless of the scientific rigor you apply to your monitoring efforts, mapping your locations using a GPS is the easiest way to share the information with regulatory agencies and other collaborators with the project, but hand-mapped locations on a topographic map can be just as informative and useful.
For a simple monitoring protocol, returning to your release sites in the fall and spring of each year and determining an approximate percentage of control can be done, along with looking for evidence of increase in the beetle population and activity. Photo points are also simple to set up, when loosestrife is in full bloom. Find a location in a release site that is easy to return to every year; you can mark it yourself or use an existing landmark. Photograph that site annually, in fall and spring, to track visually the damage your beetles have done.
For a more rigorous monitoring effort, using quadrats (1 meter-squared plots made from a durable material such as pvc pipe) in specific locations that are measured twice annually can give you a wealth of data on your project. A sound scientific monitoring protocol was used at the Goodyear Swams Sanctuary, and can be found here: http://www.oneonta.edu/academics/biofld/PUBS/ANNUAL/2005/Monitoring%20the%20biocontrol%20of%20purple%20loosestrife%2005%20v2.pdf
The monitoring protocol consisted of biennial monitoring, in spring and fall. The spring monitoring involved determining the abundance of Galerucella at each life stage (egg, larvae, and adult), in 1 meter-squared quadrats, along with estimation of percent cover of loosestrife, measurement of the five tallest loosestrife plants in the quadrats, and the amount of damage to the plants that could be confidently attributed to Galerucella feeding activity. Fall monitoring measured the same variables, along with native plant cover in each quadrat as well.
The above monitoring protocol was developed by Bernd Blossey, and can be found in the paper Impact and Management of Purple Loosestrife (Lythrum salicaria) in North America: (http://www.massaudubon.org/Lessoning_Loosestrife/documents/G._Background_Materials/4._Research_on_Impact_of_Purple_Loosestrife.pdf ) and at Bernd Blossey’s site: http://www.invasiveplants.net/monitor/pl_monitor.aspx
This paper, and indeed a large portion of Bernd Blossey’s published works, are all excellent sources of information on invasive species biocontrol programs. He is currently working at Cornell University, and his webpage can be found here: http://www.invasiveplants.net/
This is by no means a complete list of projects that have involved a Galerucella beetle release, but this list includes projects I’ve found helpful, as well as ones that I think others will find helpful. Feel free to comment with information about other Galerucella projects to add to the list!
These and other projects that have detailed how they reared and released Galerucella beetles are a goldmine of tips and tricks to having a successful project. You can use the successes and shortcomings of other projects to guide your own, providing you with a blueprint that will improve your chances of a successful release.
The University of Minnesota has an extremely detailed and thorough guide to rearing Galerucella beetles. It goes step-by-step for the whole rearing process and includes diagrams, which can be very helpful to those of us who are visual learners. It also provides a wealth of information on the life cycle of the beetles themselves, as well as some suggestions for replacing purple loosestrife once the beetles have done their job.
Biological Control of Purple Loosestrife: A Guide for Rearing Leaf-feeding Beetles, University of Minnesota:
The Rachel Carson National Wildlife Refuge has provided another great guide to rearing Galerucella beetles, including both a general step-by-step guide and a personal account of the challenges encountered in a 2006 rearing process the Refuge took part in. It is a great source for tips on rearing beetles. They also have an established monitoring protocol for their project, providing data on how successful they’ve been.
Galerucella rearing guide, Rachel Carson National Wildlife Refuge: http://www.yorkswcd.org/photogallery/Invasives%20Files/Beetle%20Rearing%20Protocol.pdf Monitoring data: http://www.weedcenter.org/outreach/media/biocontrol/engage.swf
The University of Nebraska-Lincoln has a very visually appealing guide to rearing Galerucella beetles. This guide includes photographs of their setup, and directions for both one-year projects and more permanent, several-year projects. It also includes the excellent idea of using large zip ties to secure the nets to the pots; we will have to employ this idea next year!
Rearing and Releasing Galerucella Beetles to Control Purple Loosestrife, University of Nebraska-Lincoln:
The University of Connecticut extension program has another good guide, with simple instructions and good photographs of the process to help you in your design. They link back to the University of Minnesota guide as well, showing just how connected the science community can be about invasive plant management. They also have a site where people can sign on to become “beetle farmers” or report loosestrife sightings.
Homegrown Beetles: Backyard Biocontrol, University of Connecticut Invasive Plant Management: http://www.hort.uconn.edu/ipm/general/biocntrl/homebeetles.htm
The Wisconsin Department of Natural Resources has a long-standing and expansive program to rear Galerucella beetles for purple loosestrife control. This guide is meant for landowners to use for raising loosestrife beetles on their own, and is thorough and informative.
How to Raise and Release Galerucella Beetles for Controlling Purple Loosestrife in Wisconsin, Wisconsin DNR: http://dnr.wi.gov/org/es/science/publications/appendix2.pdf
The City of Cambridge, Massachusetts, has performed releases of loosestrife and involves local volunteers in monitoring projects. It is an excellent example of community engagement with regards to invasive species.
Purple Loosestrife Control Project, City of Cambridge, Massachusetts: http://www2.cambridgema.gov/CWD/purpleloosestrifebiocontrol.cfm
The Michigan Sea Grant program has classroom activities for teachers relating to purple loosestrife, including a guide to rearing and releasing beetles geared toward fulfilling education requirements while teaching kids about the world around them and the invasives that inhabit that world.
The Purple Pages, Activity Seven: Beetle Release, Michigan Sea Grant Program: http://www.miseagrant.umich.edu/ais/pp/activity_seven.htm
Cornell University has a wealth of information on biocontrol agents for invasive species, including a very thorough protocol on monitoring Galerucella beetle damage after it has been released. This information can be found at: http://www.invasiveplants.net/
The Brice Prairie Conservation Association has done annual reporting and documentation of their Galerucella project for several years in a row, and has excellent information about how a long-term Galerucella project could be run.
Purple Loosestrife Control Project, The Brice Prairie Conservation Association: http://www.briceprairieconservation.org/loosestrife/
The Bugwood Wiki contains a very thorough guide on obtaining biocontrol agents for purple loosestrife. It includes field methods and guidelines for purchasing the biocontrol agents, including how to make sure the source is high-quality and what questions to ask suppliers.
Obtaining Purple Loosestrife Biocontrol Agents, BugwoodWiki:
There are plenty of other projects being done across the nation to release Galerucella beetles. The above guides can provide you with the information you need to get started on contributing to the control of purple loosestrife. Let us know if you’d like your own project mentioned here!
Every project that involves live animals, live plants and the outdoors will have challenges, and our Galerucella rearing project is no exception. Here I’ll detail some of the challenges we came up against in rearing our beetles; hopefully others can gain from our experiences!
The first challenge was collecting the beetles; continuous poor weather in May meant collecting beetles was delayed until late May. The weather the day we collected was questionable, at best, but it was also the only day that entire week that wasn’t threatening thunderstorms.
Galerucella beetles are most active on sunny, warm days, and while our collecting day was warm, it was cloudy. The beetles had to be carefully hunted out, and there was ample evidence they had already begun breeding (both eggs and larvae were visible in the field). While this was excellent news for the release site, it raised concerns that we would have beetles totally finished laying eggs, meaning our releases in July or August would be scanty.
Thankfully, we were able to collect enough beetles to inoculate 18 plants, and they laid quite a few eggs which have hatched into quite a few larvae. I was lucky enough to get to work with the West Virginia Department of Agriculture on the beetle collecting, and was thankfully smart enough to trust their guidance that the weather was good enough for collection. Had I waited for a more favorable day I might have missed the egg-laying window for the beetles. Thank you, WVDA!
The cages were taped down with duct tape, but this proved unreliable during the incredibly wet spring we had. I found a few escaped beetles on the bare plants we left in each pool, and found a gap in the tape holding down a sleeve cage as the culprit. After returning the beetles to a different cage, I re-taped the sleeve cage, and added a rubber band seal to each pot (tying together several rubber bands to reach around the pot). This has worked well so far, but in the heat the rubber bands may snap. A higher-strength tape like Gorilla tape may be the answer to keeping the cages firmly affixed to the pots, or using a large zip-tie.
For a few of the smaller loosestrife plants, the beetles were a little too successful in laying eggs, as the larvae have nearly obliterated the plant and as a result started squeezing through even the no-see-um netting in search for new plants. My solution to this was to examine the cages daily to find escaped larvae, and transplanting them to a cage with a larger plant that can sustain more larvae; a little time consuming, but it meant that few if any larvae were lost and they could still be released into the field. Next time I may attempt to only use larger plants or larger root masses, or perhaps grow two plants per pot to increase the mass of the loosestrife available for the beetles.
While there have been a few challenges in raising the beetles, it has been fascinating and rewarding to watch them grow and demolish purple loosestrife. It will be worth the time spent raising them to see a large patch of loosestrife brought down to a manageable few plants a few years after the beetles are released!
Invasive species are often spread unwittingly by people simply enjoying the outdoors, hiking, biking, hunting, fishing, boating, or general recreation activities. Purple loosestrife creates thousands upon thousands of seeds per plant; plants like garlic mustard, thistles and invasive grasses all generate huge numbers of seeds as well. Loosestrife root fragments can also generate new plants; Japanese knotweed is another invasive that can propagate vegetatively, and root fragments from several other invasive species can generate new plants as well.
A large purple loosestrife infestation, capable of producing millions of seeds
The seeds and plant materials of invasive species can work their way into clothing, shoe and tire treads or stow away in gear and in a pet’s fur, and thus manage to travel far from their original infestation and start a new one wherever they land.
There are several very simple activities that can be done to prevent movement of invasive species:
- Wear clothing and footwear that are not “seed friendly”. Avoid bulky knits as your external layer, try to wear gaiters to prevent seeds from sticking, and wear low tread shoes or boots wherever possible to avoid buildup of seeds and debris in the tread.
- Clean your equipment before you bring it in to or out of an activity location, making sure to remove seeds and other living material. This can include your clothing and footwear, your vehicles (including boats, trucks, cars, ATVs), trailers, the fur and feet of any animals you have brought to use while hunting or trapping (i.e. hunting dogs), any traps used, bags used to carry equipment, bilges and live wells on boats, etc.
- When you do remove seeds or other materials from your clothing and equipment, do not do so in or near a waterway; this can increase the spread of invasive species.
- When moving off trail, attempt to avoid areas that are infested with invasive species. Not only can they be spread by contact with humans or animals, but some can cause irritation or damage to skin.
- Attempt to stay on trail with motor vehicles, and attempt to minimize soil disturbance wherever you spend time outdoors. Disturbed soil is prime habitat for invasive species, and minimizing disturbance will reduce the habitat available.
If you hop into a wetland that looks like this, make sure to clean your clothing, boots and equipment before leaving, to prevent the spread of purple loosestrife!
A little diligence can drastically reduce the spread of invasive species. Spreading the word to friends and family can further reduce the spread, and engage more people in efforts to prevent invasive species spread.