Community-based HWA Predator Beetle Releases

How to Protect Hemlocks in your Community

Do it yourself or work with others?

Whatever works for you will make a difference for hemlocks

Releases of the Sasajiscymnus tsugae (aka Sasi or St) predator beetle in residential areas will have an impact on hemlocks across entire neighborhoods and communities! These highly mobile beetles will fly from tree to tree and lay eggs wherever they find Hemlock Woolly Adelgid ovisacs, leaving their eggs and larvae behind to feed on HWA concentrations, then develop into new adults and repeat the cycle. Meanwhile, the mature adults keep searching for new sites for feeding and egg-laying.

Procedures for a DIY Predator Beetle Release

With a little advance planning (optimally during the period between November and February), a predator beetle release can be as easy as One-Two-Three:

One:  Get a map or plat of the area that you would like to protect. You don’t need anything fancy – an old survey plat or a printout from your county GIS records will do just fine. Then do a walk-about (or drive-about), mapping the hemlocks in your target area on this paper document.

Two:  Note the number, size and health of the hemlocks at the locations that you have identified, and check for the presence of white HWA ovisacs (which should be visible during this period). Note the “food supply” for the predator beetles on your map of potential beetle release sites.

Three:  Decide how many beetles you want to release and pick the sites that will achieve best physical coverage of the area. Then divide the number of beetles by the number of sites to determine how many to release at each site. For practical purposes, this should not be below 25 beetles per site or 100 per release area. If it is, just reduce the number of release sites.

Finally, when your beetles arrive, get them out on your hemlocks, ASAP. For large trees without lower foliage, you can attach #4 cone coffee filters to the tree. But if there is lower level foliage with HWA ovisacs present, just apply the beetles directly to the branches with a cheery “Bon appetit”!

But if you don’t want to bother with a site survey, then just release all the beetles in one central hemlock location that has plenty of food/HWA present. This will initiate beetle reproduction in that location. And then the predator beetles will do the scouting and distribution for you!

Doing Predator Beetle Releases with Others

Getting municipal or county groups involved can greatly expand the scale and funding of predator beetle releases. And local “green” groups can also provide an effective organizational base for predator beetle releases. So look to local groups that have either environmental or economic interests in preserving our native hemlock environments. Whether it’s a conservation group, trout fishing club, local park, camp or land trust, all are candidates for participation in a community-based biological control effort for HWA.  Remember that every participant added to your community biocontrol effort will multiply the scope of HWA control for hemlocks in the places where you live, work, and enjoy.

Sasi (Sasajiscymnus tsugae) Predator Beetles 

Responding to a Hatch of HWA Nymphs…. Let’s Eat!

Sasi Beetles Feeding on Emerging HWA Larvae

Getting HWA Predator Beetles Out in Your Community – An NC Case Study

One community organization that is well-positioned to help protect our native hemlocks from destruction is your local conservation land trust. Here in Western North Carolina, I have worked with several different local Land Trusts to release HWA predator beetles. But Carolina Mountain Land Conservancy (CMLC) has participated in the most extensive biological control efforts to protect both Eastern (Tsuga canadensis) and Carolina hemlocks (Tsuga caroliniana) over a multi-county area.

In 2012, CMLC Stewardship Director Julia Brockman initiated a program to release 900 predator beetles to help an old-growth Carolina hemlock colony on a recently acquired CMLC property in Hickory Nut Gorge. In 2013, her successor, Sarah Fraser, followed up on this biocontrol effort by releasing 1500 Sasi predator beetles on a larger Carolina hemlock colony, located on the same property. (See Weed Patch Mtn photos on Biological Control page.) And in 2014-15 Sarah extended CMLC’s HWA biological control efforts to include eastern hemlocks (Tsuga canadensis) on CMLC conservation easements, offering cost-share purchases for Sasjiscymnus tsugae predator beetles with releases provided by CMLC volunteers and staff.









The map below shows the geographical scope of Carolina Mountain Land Conservancy’s outreach to protect and restore our native hemlock populations, resulting in the release of 20,000 HWA predator beetles on over 100 properties through 2016! And over 10,000 of these releases have involved the reclusive Carolina Hemlock (Tsuga caroliniana), in colonies distributed along rock faces, as shown above.


This case study shows what a motivated environmental group can do to protect and restore our native hemlocks and their associated woodland, riparian and bluff-top ecosystems. But environmental motivation is not always enough to promote group action! Individuals can also play a role in this process with donations of time and funding in support of an HWA biological control effort!

Remember that hemlock restoration for all private hemlock areas in the eastern US is within our reach, but establishing predator beetles can only proceed one property at a time. And you are in a position to determine where and when this restoration occurs in your area!

A Note of Caution on USDA Assessments of Predator Beetle Releases

In community release ventures there will often be some well-intended individual who wants to ask USDA, County Extension or Forest Service personnel about a private community predator beetle release. But unfortunately, USDA and USFS are mired in a failed research protocol fiasco which can lead them to misinform private property owners, as well as one another, about successful HWA control practices. (For more information on assessing HWA predator beetle releases, go to Assessment.)

Over the last ~15 years USDA/USFS have initiated HWA biological control strategies on public lands, including National Parks and Forests that have released millions of Sasi and other HWA predator beetles. USDA/USFS still advises private individual and community property-owners not to implement HWA biocontrol on hemlock areas, directing them instead to short-term neonicotinoid insecticide applications on individual trees. So what is the USDA environmental policy behind using long-term biological control strategies for HWA on public lands to protect entire areas of wild hemlocks, but recommending only short-term chemical controls for individual hemlock trees on private lands???

Chemical insecticides can certainly play a role in protecting larger trees while establishing a predator beetle population to protect an entire hemlock area. (See IPM page for information on combining chemical & biological strategies to control HWA on private properties.) But remember that only biological control of HWA can enable long-term hemlock restoration and recovery!

One possible source of USDA/USFS resistance to private biological control efforts is the use of a predator beetle assessment strategy that reports collecting low numbers of Sasi beetles in ground-level sampling efforts. However, it is important to note that this ground-level sampling assessment strategy had already proven to be ineffective for assessing another mobile predator beetle over 30 years ago – when it failed to detect the success of USDA releases of Harmonia axyridis (the Asian Lady Beetle)!

“During the late 1970s through the early 1980s, tens of thousands of multicolored Asian lady beetles were intentionally released by the U. S. Department of Agriculture’s Agricultural Research Service (USDA-ARS) in an effort to control insect pests that injure trees. The USDA-ARS coordinated the lady beetle releases in many southern and eastern states, including Ohio, Maine, Connecticut, Delaware, Pennsylvania, Maryland, Georgia, Mississippi, and Louisiana. … The USDA-ARS release program was eventually discontinued because failed recapture efforts suggested that the multicolored Asian lady beetle was not surviving in the United States.”                                        Source:  (emphasis added)

But the failures that occurred in these USDA releases did not involve failures in establishing populations of these highly mobile Asian-origin predator beetles. Nor did they involve failures in these beetles’ effectiveness in controlling aphid populations on agricultural crops, as intended. Instead, the failure was in the “beetle capture” protocol in which ground-level sampling for these active adult beetles consistently failed to detect the increasing beetle populations for nearly a decade — at the same time as these Asian Ladybug beetles were swarming on human structures throughout release areas!

                                                                                                         Not surviving in the US?

Harmonia axyridis

Science note: Any researcher can make the mistake of using an unreliable and/or nonvalid method the first time. But using such a method repeatedly, under conditions where its methodological failure has already been clearly demonstrated, is contrary to sound scientific practice.

The result of using such non-valid methods in a research effort is to replace scientific knowledge with ignorance, and this has lead USDA and the US Forest Service to promote ignorance-based policies and practices concerning HWA predator beetles.

Implications:  Ground-level sampling for insects is a time-honored entomological method that works well for many insects – where high insect mobility is not a relevant variable. But the above-noted research failure shows that with a highly mobile predator beetle, such as Harmonia axyridis, this ground-level sampling method does not produce valid insect population information. Therefore, the practice of using ground-level sampling methods to assess population numbers for other highly mobile predator beetles, such as Sasjiscymnus tsugae, (which is also positively phototaxic – attracted to light and hence upper foliage areas), should be considered an exercise in futility. And this use of a non-valid assessment strategy, raises the specter of scientific malpractice on the part of USDA policy-makers.

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