What are Biocontrols?

The terms biocontrol or biocontrols refer to using one species to control another. One of the biggest reasons that invasive species are able to have such an impact on ecosystems is that they often lack natural predators in the areas they are introduced to. Biocontrols can be used to control invasive species. This involves bringing natural predators from areas where the invasive species is native and releasing them in the ecosystems in which you want to control the invasive.  

Biocontrols can offer a long-term solution for the suppression of many widespread invasive species. However,  biocontrols are not a “solve-all” solution. For a biocontrol to be approved for release it undergoes intensive research and trials to ensure that applied biocontrols will only impact the target species. This process can take a long time to complete. In addition, there aren’t approved biocontrols available for every invasive species, and it can take multiple years for released biocontrol populations to become established enough to make a difference. In New York, biocontrols have been successfully used to suppress purple loosestrife, and there are approved agents being released in the state to control hemlock woolly adelgid, emerald ash borer, and swallow-wort. You can learn more about biocontrol research being done in NYS at the New York State Invasive Species Research Institute, as well as in this USDA Field Guide

Biocontrol Program Overview

Emerald Ash Borer (EAB) Biocontrol:

We’ve released three species of parasitoid wasps (Spathius galinae, Tetrastichus planipennisi, and Oobius agrili) that target EAB at Rice Creek Field Station (SUNY Oswego).  We’re currently in the monitoring stage of our EAB biocontrol program and have set up pan traps to detect if populations of the parasitoid wasps have become established. We’re recruiting volunteers to assist with surveys held each week on Wednesdays ending on September 25th, 2024. Volunteers will collect specimens from 15 pan traps located along walking trails at the Rice Creek Field Station. Specimens will be analyzed under microscopes at the station lab. Learn more about this opportunity and sign up to join us!

Spathius galinae a biocontrol for Emerald Ash Borer. © SLELO PRISM/TNC

Swallow-wort Biocontrol:

We have four cages set up for Hypena opulenta moths- the biocontrol for swallow-wort; two of these are at Wehle State Park, and two of these are at Grenadier Island.

2024 Total Released (all cages): 150 Adults (75 M, 75 F), 150 Pupae, 325 Larvae (released outside cages (1/2 at Wehle, 1/2 at Grenadier (162/163))

By Cage:

  • Grenadier Cage 1: 37 Adults (19 M, 18 F), 38 Pupae
  • Grenadier Cage 2: 38 Adults (19 M, 19 F), 37 Pupae
  • Wehle Cage 1: 37 Adults (18 M, 19 F), 38 Pupae
  • Wehle Cage 2: 38 Adults (19 M, 19 F), 37 Pupae


Hemlock Woolly Adelgid (HWA) Biocontrol:

1,969 Leucotaraxis piniperda silver flies were released at Selkirk Shores SP on May 23rd.  1,998 Leucotaraxis piniperda silver flies were released at Mexico Point SP on April 16th. The biocontrol insects are provided by the New York State Hemlock Initiative. 

Leucotaraxis piniperda a biocontrol for Hemlock Woolly Adelgid. © SLELO PRISM/TNC

Swallow-wort Biocontrol in SLELO

Native to Ukraine, swallowwort was likely introduced to North America as an ornamental plant, soon
spreading to several northeastern states. The plant creates extremely dense monocultures spreading over
acres upon acres of otherwise biologically diverse natural systems. The biological control, Hypena opulenta, is
also from the Ukraine and feeds exclusively on swallowwort.

Partnering with the NYS Invasive Species Research Institute, the Thousand Islands Land Trust, SUNY ESF,
University of Rhode Island, the USDA Agricultural Research Service and local volunteers, our SLELO PRISM
assisted with caged releases of Hypena opulenta at four sites within the Eastern Lake Ontario and St. Lawrence
Region. This important work will help to restore Priority Conservation Areas (PCA’s) to their natural ecological

Identifying Hypena opulenta

Hypena opulenta adults are one cm long with a wingspan of about 3cm. They have dull, light brown forewings with a dark band in the middle and hindwings that are pale orange. 

The larvae start out white, but later become green with black spots and a yellow head. 

The life cycle of Hypena starts with the emergence of the egg as a larva.  This larva goes through five stages or instars. The last molt occurs at the end of the 5th instar in which the larva transforms into pupae.  Metamorphosis occurs inside the pupa and results in the emergence of an adult-winged moth. 

Adult Hypena opulenta lay between 400 to 600 eggs during an average 2-3 week lifespan.  Two generations may occur in the same year. H. opulenta larvae feed exclusively on pale and black swallowwort making them a prime candidate for biocontrol. 

Photos from the field

Hypena opulenta pupae being readied for release.

Pupae remain in the release bucket until they mature into egg-laying adults inside the screened cage. 

One of four 6’x6’x6’ research cages.

Adult Hypena opulenta emerged from pupae. 

Cage Monitoring Stats & Reports

2022-23 Field Season Overviews

2021 Field Season Overview

2020 Field Season Overview

The Eastern Lake Ontario Swallow-wort Collaborative (ELOSC), is a platform for sharing the most up-to-date research and best management practices to inform stakeholders about the prevention and management of invasive swallow-wort.

Learn More About Swallow-wort

Biocontrol Webinar Recordings


Rob Williams                              rwilliams@tnc.org                     Program Director

Megan Pistolese megan.pistolese@tnc.org
Outreach and Education

Brittney Rogers brittney.rogers@tnc.org 
Aquatic Invasive Species

Robert Smith       robert.l.smith@tnc.org 
Terrestrial Invasive Species

During this time the best way to contact our team is via email.