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Plant Protection and Quarantine

Biological Control Program Annual Report

Fiscal Year 2023

March 2024

Agency Contact:

Office of the Deputy Administrator

Plant Protection and Quarantine

Animal and Plant Health Inspection Service

United States Department of Agriculture

4700 River Road

Riverdale, MD 20737
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Executive Summary

This annual report describes the major accomplishments and activities for the Animal and Plant 

Health Inspection Service (APHIS), Plant Protection and Quarantine (PPQ), Biological Control 

program in fiscal year (FY) 2023. The report highlights the program’s mission and operating 

principles, key program level accomplishments including approval of a comprehensive strategic 

plan, and completion of a Regulated Domestic Pest Program Evaluation Committee (RDPPEC) 

program review. The report highlights outreach efforts, subject matter expert committee 

affiliations, and provides appendices that list current Biological Control targets including agents, 

and the stage of project development, and a list of Plant Protection Act (PPA),7721, Plant Pest 

and Disease Management and Disaster Prevention Program leveraged biological control projects.

Key accomplishments and highlights are presented for Field Operations implementation efforts, 

Science and Technology’s (S&T) research and methods development work, and Pest Exclusion 

and Import Programs recent biological organism permitting actions. In FY23, the program 

provided national program oversight for both insect and weed biological control activities. Field 

Operations provided funding and oversight for 31 cooperative agreements with organizations in 

22 different states that will rear, release, and monitor the establishment and impact of 16 agents 

attacking 3 invasive arthropods and 14 exotic weeds. S&T supported the coordination of research 

projects against 33 targets. Scientific research is focused on advancing research and data 

collection towards evaluation for U.S. permitting of 19 potential agents, as well as advancing 

methods development for rearing and release of 24 agents. Taken together, these activities and 

efforts demonstrate consistent progress towards the future and sustainability of the PPQ 

Biological Control program and the facilitation of environmentally sustainable pest management 

solutions that will help mitigate the economic and environmental impacts of invasive plant pest

species.

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Contents

Executive Summary............................................................................................................................................................. 2

Biological Control Cross Functional Working Group........................................................................................ 5

Program Mission and Operating Principles........................................................................................................... 5

Key Program Highlights .................................................................................................................................................... 6

Completed Strategic Plan ................................................................................................................................................ 6

Completed Full Review of the Biological Control Program by the Regulated Domestic Pest 

Program Evaluation Committee (RDPPEC)............................................................................................................. 6

Outreach and Education................................................................................................................................................... 7

Committee and Expert Group Activities.................................................................................................................... 8

Key PPQ Priority Pests and Program Support...................................................................................................... 8

Emerald Ash Borer............................................................................................................................................................. 9

Spotted Lanternfly............................................................................................................................................................10

Box Tree Moth....................................................................................................................................................................10

Asian Citrus Psyllid ..........................................................................................................................................................11

Field Operations..................................................................................................................................................................11

Key Invasive Species Targeted....................................................................................................................................11

Olive Psyllid....................................................................................................................................................................11

Russian Wheat Aphid .................................................................................................................................................12

Spotted Wing Drosophila..........................................................................................................................................12

Air Potato ........................................................................................................................................................................12

Black and Pale Swallowworts.................................................................................................................................12

Bohemian, Giant, and Japanese Knotweeds......................................................................................................13

Common Crupina .........................................................................................................................................................13

Gorse .................................................................................................................................................................................13

Hoary Cress ....................................................................................................................................................................13

Houndstongue...............................................................................................................................................................14

Puncturevine..................................................................................................................................................................14

Yellow Starthistle.........................................................................................................................................................14

Yellow Toadflax ............................................................................................................................................................15

Science and Technology ..................................................................................................................................................15

Key Research by Target Species .................................................................................................................................15

Asian Bean Thrips........................................................................................................................................................15
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Bemisia tabaci, Tuta absoluta .................................................................................................................................15

Brazilian Peppertree...................................................................................................................................................16

Brevipalpus yothersi....................................................................................................................................................16

Phantasma scale ...........................................................................................................................................................16

Roseau cane scale ........................................................................................................................................................17

Shot Hole Borer.............................................................................................................................................................17

Pest Exclusion and Import Programs ......................................................................................................................17

Appendix A: FY23 Biological Control Target, Agent, and Stage of Project Development........................19

Appendix B: FY23 PPA 7721-funded biological control projects. .....................................................................25
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Biological Control Cross Functional Working Group 

The Biological Control cross functional working group’s (CFWG) goal is to increase the 

cohesion, efficiency, and effectiveness of the PPQ Biological Control program. The Biological 

Control CFWG coordinates activities related to the PPQ Biological Control program across four 

PPQ Core Functional Areas (CFAs):

• Emergency and Domestic Programs (EDP); Biocontrol, and Forest, Wood, and 

Rangelands Pests (BFWRP) – Ron Weeks

• Field Operations (FO) – Keith Colpetzer

• Science and Technology (S&T) Domestic and Emergency Scientific Support (DESS) –

Tara Holtz and Ashton Leo

• Pest Exclusion and Import Programs (PEIP), Permitting and Compliance Coordination 

(PCC) – Bob Pfannenstiel

Program Mission and Operating Principles

The PPQ Biological Control program promotes, facilitates, develops, and delivers safe and 

effective biological control through partnerships with other federal, state, tribal, and private 

organizations that can be used either alone or in combination with other control tactics to help 

reduce the economic losses and negative impacts of non-indigenous, invasive pests to America’s 

agricultural production and natural areas.

The program invests in the discovery, development, and deployment of new, non-native agents 

(i.e., parasitoids, predators, herbivores, or pathogens) and through surveys, basic research, and 

methods development that locate and exploit biological control agents. The program supports the 

development of more efficient and improved operational methods for biological control 

implementation. Permitting and Compliance Coordination manages the compliance activities 

required under the authority of the Plant Protection Act for approval of PPQ 526 permits for the 

importation, interstate movement, and environmental release of biological control organisms of 

plant pests and weeds.

Limited resources and the continued pressure of invasive pests on American agriculture and 

natural resources make it impractical for PPQ alone to maintain the necessary resources, 

infrastructure, space, and scientific expertise to effectively sustain the overall Biological Control 

program. PPQ’s Biological Control program actively seeks and maintains partnerships with tribal 

governments, state agencies, federal agencies, and universities to be better prepared, equipped, 

and more efficient in carrying out the agency’s biological control mission. 

PPQ uses cooperative agreements, inter-agency agreements, and Memoranda of Understanding 

(MOU) to leverage and sustain PPQ’s biological control projects. These partnerships establish 

mutual cooperative relationships which PPQ and interested partners can use to develop, 

implement, and sustain the Biological Control program. PPQ consultation and active 

collaboration with these partners include discussions and determinations of cost-sharing, 
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prioritization of target pests, availability of funding, infrastructure issues, and leveraging of other 

resources. 

The program leverages significant PPA 7721 funding to complete biological control projects. 

PPA 7721 projects ranged from native natural enemy surveys, completion of host range testing, 

rearing of non-target hosts for testing, development, and approval of a first-time release permit, 

rearing and development of rearing systems for targets and/or hosts, initial release and data 

collection protocols, and field establishment verification studies after first time releases. 

In FY23, 25 PPA 7721 biological control projects were approved for $5,255,706.25 in funding 

(see Appendix B List of FY23 PPA 7721 biological control projects). 

Key Program Highlights

Completed Strategic Plan 

PPQ’s BC Strategic Plan describes the program’s mission, vision, and strategic milestones. The 

strategic plan includes specific goals, objectives, and deliverables to accomplish the agency’s 

biological control regulatory functions and program mission. These strategic goals provide a 

traceable framework to ensure that the PPQ Biological Control program is responsive, 

sustainable, efficient, measurable, and valued by PPQ and its stakeholders. It provides five long 

term goals with supporting objectives, and deliverables. The plan can be found on the PPQ 

Biological Control internet site. 

Completed Full Review of the Biological Control Program 

by the Regulated Domestic Pest Program Evaluation 

Committee (RDPPEC) 

The RDPPEC reviewed program documents provided by the Biological Control CFWG and the 

group’s responses to questions raised by the RDPPEC. Based on the information provided by the 

CFWG, the RDPPEC believes that the Biological Control program provides a beneficial, unique 

service in researching the feasibility, applicability, and rearing of appropriate biological control 

agents for targeted pests of concern. The RDPPEC recognized key areas (communication, 

process, and implementation) within the Biological Control program that could benefit from 

increased focus and development by the CFWG and support by PPQ Management. In 

conjunction with the Biological Control strategic plan, these recommendations will help facilitate 

the development of safe and sustainable biological control options and guide program activities 

now and into the future. The Recommendations document can be found on the PPQ Biological 

Control internet site. 
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Outreach and Education

On November 7, at the Entomological Society of America meeting in National Harbor, MD, 

PPQ S&T scientist Dr. Juli Gould was presented the Distinguished Scientist award by the 

International Organization of Biological Control Nearctic Regional Section. This award 

celebrates a member of the organization who has made significant contributions to biological 

control. Prior to receiving her award, Dr. Gould gave a seminar on her career’s work in 

developing and implementing biological control; she highlighted her successful work on 

implementing biological control of ash whitefly and emerald ash borer.

Increasing awareness and understanding of the biological control process and successes, enhance 

PPQ and stakeholder knowledge and continued use of biological control solutions. The 

Biological Control CFWG participated in several key stakeholder engagement sessions in FY23

to share information and enhance awareness about PPQ’s biological control development and 

delivery process. 

Below are additional outreach and education accomplishments the CFWG completed this year.

• Completed delivery of three biological control intra-agency webinars that covered key 

program areas such as permitting, operations, and a historical perspective of APHIS 

Biological Control. Result was increased program information sharing to participants

within PPQ that attended the 3-part series. 

• Presented “Overview of PPQ’s Biological Control Strategic Plan” at National Plant 

Board meeting in Little Rock AR. Result was communication and stakeholder support of 

national program goals, objectives, and performance measures to audience of over 100 

PPQ and NPB representatives. 

• Participated in Colorado Department of Agriculture’s (CDA) Palisade Insectary Webinar 

(Stakeholder engagement and partnership development). Result was initiation of a new 

cooperative agreement that will support regional rearing and release of a weevil 

(Ceratapion basicorne) to help control yellow starthistle, an invasive weed found in 40 of 

the lower 48 states. Impact is continued regional collaboration with stakeholders that 

advance the biological control program and leverages state and federal capabilities.

• Presented an overview of the APHIS Biological Control Program to the National Plant 

Protection Organization of Taiwan, the Bureau of Animal and Plant Health Inspection 

and Quarantine, during which we discussed partnering with other organizations and 

leveraging other organizations’ resources to accomplish a shared goal more efficiently.

• Delivered two program presentations to visiting representatives of the Taiwan Bureau of 

Animal and Plant Health Inspection and Quarantine. Presentations covered; 1) an 

overview of the biocontrol program including program mission, project types and 
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selection, project development and facilitation activities, and working with cooperators 

and 2) APHIS regulation and permitting of biocontrol agents. 

• Presentations on the regulatory process for approving the introduction of biological 

control agents and an updated list of current petitions were given at the Montana Weed 

Biological Control Meeting and to Biopesticide permitting section of the EPA. 

• A section was created on the APHIS environmental compliance process for the North 

American Invasive Species Management Association Biocontrol 101 Short Course. 

NAISMA Biological Control 101 Short Course

• Participated in a meeting with the National Association of State Foresters where we 

discussed opportunities to partner on shared biological control goals. 

Committee and Expert Group Activities 

Biological Control CFWG members served as APHIS PPQ Biological Control representatives as 

part of NAPPO Biological Control Export Group – “Revision of RSPM 26 - Certification of 

commercial arthropod BCAs or non-Apis pollinators moving into NAPPO member countries”. 

The CFWG’s work strengthened international collaboration and development of regional 

standards that support and facilitate the use and development of biological control pest 

management solutions in North America.

Biological Control CFWG members also served as APHIS PPQ Biological Control experts and 

TAG members at 2023 Hybrid Annual TAG Meeting. PPQ provided guidance to researchers and 

expert advice on recommendations for or against the release of biological control agents, based 

on considerations of potential non-target impacts and conflicts of interest.

FY23 Portfolio of Biological Control Targets, Agents, and 

Stage of Project Development 

See Appendix A 

FY23 List of PPA 7721 Biological Control Projects 

Supported 

See Appendix B 

Key PPQ Priority Pests and Program Support 

PPQ’s Biological Control program provides scientific, practical, and technical support for 

specific pest biological control programs funded by PPQ under other funding lines. With many 
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years of experience and partnership connections on these types of programs, the PPQ Biological 

Control community of scientists can assist in the development and completion of these programs.

Emerald Ash Borer

The emerald ash borer (EAB, Agrilus planipennis) is a destructive wood-boring pest of ash trees 

(Fraxinus spp.). EAB was first found in Michigan in 2002. Today EAB is in 36 states and the 

District of Columbia. Exploration for EAB natural enemies in China, Russia, and Korea has 

yielded several hymenopteran parasitoids, and four species have been approved for release as 

biological control agents of EAB in the United States and others are under consideration (see 

Appendix B). 

Releases

During the 2023 season, APHIS, and its biological control partners, released parasitoids in 35 

new counties. These releases bring the program’s total number of releases to 453 counties in 32 

states and the District of Columbia.

Table 1. Biocontrol Agents Release January 1 - October 31, 2023

Biocontrol Agents Release

January 1 - October 31, 2023

Amount

Oobius agrili 207,463

Spathius agrili 8,494

Spathius galinae 107,399

Tetrastichus planipennisi 163,268

Total 486,624

Recoveries

To date, parasitoids have been recovered in 23 states: Colorado, Connecticut, Delaware, Illinois, 

Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, 

Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, 

Tennessee, Virginia, Wisconsin, and in 2 Canadian provinces: Ontario and Quebec. This means 

the wasps are establishing, reproducing, and killing EAB.

S&T continues to work with partners to assess the population level impacts on EAB leading to 

several key publications that illuminate the impact of parasitoid releases in the United States. 

PPQ S&T and State University of New York, College of Environmental Science and Forestry 

evaluated insecticide treatments, parasitoid releases, forest regeneration, release efficacy at earlyand post-invasion locations. This led to the development of a manuscript documenting 

regeneration of ash in forest stands where EAB killed most of the mature trees. 

• Morris, T. D., Gould, J. R., Drake, J., & Fierke, M. K. (2023). Status of ash forests and 

regeneration a decade after first detection of emerald ash borer infestation in New York 

state. Forest ecology and management, 549, 121464.
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A second publication shows that EAB parasitoids released in forest stands where most mature 

trees have been killed and EAB densities have collapsed have a significant impact. The impact of 

EAB parasitoids in such stands is high: as high as in stands where parasitoids were released a 

decade earlier before EAB collapse.

• Morris, T. D., Gould, J. R., & Fierke, M. K. (2023). Establishment and impacts of emerald 

ash borer (Coleoptera: Buprestidae) parasitoids released at early-and post-invasion sites. 

Journal of Economic Entomology, 2023 Aug 10;116(4):1155-1164.

Another publication described factors affecting the distribution of EAB parasitoids in an urban 

environment.

• Morris, T. D., Drake, J. E., Gould, J. R., & Fierke, M. K. (2023). Factors affecting 

distribution of emerald ash borer parasitoids in an urban environment. Landscape and 

Urban Planning, 237, 104814.

Spotted Lanternfly

PPQ S&T is working in partnership with more than 11 cooperators to pursue biological control 

for Spotted Lanternfly (SLF; Lycorma delicatula). Host specificity testing of three haplotypes of 

Anastatus orientalis, an egg parasitoid attacking SLF, came to conclusion in FY23. The 

parasitoid attacked squash bug eggs, stink bug eggs, and silk moth eggs. It is insufficiently host 

specific for release in the United States. Further, completed life-cycle studies show that

Anastatus orientalis is not well synchronized with the lifecycle of its host.

Work continues for the nymphal parasitoid Dryinus sinicus. Improved rearing of tree-of-heaven 

plants and SLF nymphs led to the development of a robust colony of the Dryinus sinicus in 

quarantine. S&T and cooperators-initiated host specificity testing and studies of Dryinus sinicus’

life history. To date, we have not observed any non-target attack. Studies are ongoing.

Box Tree Moth

Investigations continue on the parasitoid complex of box tree moth (BTM; Cydalima 

perspectalis) in South Korea lead by CABI Switzerland. Field observations of parasitism were as 

high as 96% in some areas, with parasitism levels across urban and natural sites ranging from 43 

to 55%. Cooperators collected samples of BTM larvae and live parasitoids in South Korea and 

shipped them to the CABI facility in Switzerland to develop optimal rearing techniques and 

conduct investigations on their biology and host range testing. Of the eight primary larval 

parasitoids shipped to the CABI quarantine in Switzerland, two parasitoid species are now 

established in the quarantine laboratory and undergoing host specificity testing. These first 

results show that one of them; the ichneumonid wasp, Eriborus sp. (Campopleginae), had high 

levels of parasitism observed in the field and may be a good candidate for introduction for BTM 

classical biological control in North America (Appendix B). The most promising parasitoids will 
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be shipped to PPQ S&T to initiate host range testing with native Lepidoptera and assess potential 

non-target effects. 

PPQ S&T established trapping and collecting methods for non-target moths in the families 

Crambidae and Pyralidae in the United States. Rearing methods for individual non-target species 

are in development to facilitate host testing of promising candidates.

Asian Citrus Psyllid

PPQ S&T continues to produce Tamarixia radiata for release in Texas, Louisiana, and Mexico 

border areas. Since 2011, PPQ S&T has produced over 15.7 million beneficial insects for field 

release in Texas, Louisiana, and Mexico border areas, with 283,000 released in FY23. In FY23,

S&T completed a comprehensive rearing, release, and monitoring manual for Tamarixia radiata, 

a significant milestone contributing to the accomplishments of the program. Work also continued 

on additional biological control options to further reduce Asian citrus psyllid (ACP; Diaphorina 

citri) populations. PPQ S&T concluded studies on assessing the impact of entomopathogens for 

the integrated biological control of the ACP in the Lower Rio Grande Valley of Texas. After 

thorough primary and secondary screening, BioCeres (ANT03) and Isarid (Ifr9901, previously 

known as NoFly) emerged as promising candidates for field use. Both candidates are included in 

the list of approved crop applications in the United States. In California, PPQ S&T and Citrus 

Research Board conducted augmentative releases of three predator species, Chrysoperla 

comanche, Rhyzobius lophanthe, and Diomus pumilio and are evaluating these predators as an 

additional method of suppressing ACP in residential citrus. 

Field Operations

Field Operations provided funding and oversight for 31 cooperative agreements with 

organizations in 22 different states that will rear, release, and monitor the establishment and 

impact of 16 agents attacking three invasive arthropods and 14 exotic weeds.

Key Invasive Species Targeted

Olive Psyllid

Olive psyllid (Euphyllura olivine) is a serious pest of olives that was first detected in California 

in 2007 and is known to reduce crop yields by up to 60% in the Mediterranean basin. Our FY23 

agreement with the California Department of Food and Agriculture primarily focused on rearing, 

releasing, and monitoring for the establishment of Psyllaephagus euphyllurae, an encyrtid wasp 

that attacks and kills olive psyllid. This investment, which started in FY21, led to the release of 

the wasp into California in June 2022 when APHIS first permitted the release of this wasp into 

the United States, and it financed establishment surveys that began in July 2023.
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Russian Wheat Aphid

APHIS partnered with the Agriculture Research Service and Colorado State University to release 

Aphelinus hordei for the first time into the United States. Aphelinus hordei is a parasitoid wasp 

that attacks and kills Russian wheat aphid (Diuraphis noxia), a major pest of wheat, barley, and 

other small grains. APHIS expects this newly permitted parasitoid to establish and compliment 

Aphelinus atriplicis, a biological control agent of Russian wheat aphid that was established in the 

United States by 1996 and reportedly attacks 13-16% of Russian wheat aphid in Colorado, 

Nebraska, and Wyoming. This investment is extremely important since the Russian wheat aphid 

has evolved four virulent strains that are capable surviving and reproducing on resistant wheat 

cultivars, the industry’s primary tool for managing the aphid.

Spotted Wing Drosophila

Spotted wing drosophila (Drosophila suzukii) is a vinegar fly that damages healthy berries, 

cherries, grapes, and other soft tree fruit by cutting slits into the fruit to deposit eggs. APHIS 

increased our investments in biological control of Spotted wing drosophila in FY23 in response 

to the fly rapidly spreading throughout the United States, the high economic impacts associated 

with its spread, the difficulties experienced while trying to control the fly by other methods, and 

the availability of a newly permitted biological control agent, Gnaspis brasiliensis. FY23 

agreements focused on rearing and releasing G. brasiliensis, a parasitoid wasp that attacks and 

kills Spotted wing drosophila larvae.

Air Potato

Air potato (Dioscorea bulbifera) is a vine that grows rapidly, forms dense mats, and displaces 

native vegetation in Florida, Hawaii, and parts of Alabama, Georgia, Louisiana, Mississippi, and 

Texas. FY23 cooperator efforts concentrated on rearing and releasing Lilioceris egena, a 

chrysomelid beetle from southeast Asia that APHIS first permitted for release into the United 

States in 2021. APHIS anticipates that L. egena feeding on the reproductive structures (i.e., 

bulbils) of air potato will enhance the impacts researchers have already seen from releasing 

Lilioceris cheni, a beetle that feeds exclusively on the leaves of air potato, has established 

everywhere in the continental United States where air potato is known to occur, and has been

shown to inflict moderate to high damage to individual air potato plants growing in the 

environment and reduce the area of the United States covered by air potato.

Black and Pale Swallowworts

Black and pale swallowworts (Cynanchum louiseae and C. rossicum) are perennial vines that 

have invaded fields and forests in the northeastern United States and have been found as far west 

as Nebraska and Kansas, with satellite populations in California, and as far south as Missouri and 

Kentucky. These species can form dense stands that displace native vegetation and alter the 

composition of animal communities. Black swallowwort is an ecological threat because it 

stimulates monarch butterflies to deposit eggs even though monarch larvae cannot complete 
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development on this plant. FY23 efforts focused on rearing and releasing Hypena opulenta, a 

Ukrainian moth whose larvae feed exclusively on these plants. APHIS efforts also concentrated 

on distributing the moth to cooperators for release across the nation and on determining what 

impact the moth has had on these invasive swallowwort populations since the agency first 

permitted its release in 2017.

Bohemian, Giant, and Japanese Knotweeds

Bohemian, giant, and Japanese knotweeds (Fallopia x bohemica, F. sachalinensis, and F.

japonica) are three robust perennials that occur almost everywhere in the United States, except 

the arid southwest. They spread rapidly from rhizomes and cuttings, form dense thickets that 

displace native vegetation, reduce biodiversity, and are difficult to control. In FY23, APHIS 

cooperators worked primarily on rearing, releasing, and monitoring for the establishment of 

Aphalara itadori, a psyllid that feeds exclusively on these plants and was first permitted for 

release into the United States in 2020. To date, APHIS cooperators have released two different 

lines (i.e., the Hokkaido and the Kyushu biotype) into a variety of different habitats where 

knotweeds grow without seeing any indication of establishment. These results have not deterred 

biological control efforts, as the psyllids are difficult to detect, and a new promising biotype (i.e., 

the Murakami biotype) should be approved for field release before the Spring 2024.

Common Crupina

Common crupina (Crupina vulgaris) is a federally listed noxious weed that forms dense stands, 

displaces native vegetation, and reduces the value of range and pastureland, as the mature plants 

are not palatable to most livestock. FY23 agreements focused primarily on propagating and 

releasing spores of the fungus, Ramularia crupinae, which APHIS first permitted for field 

release in 2021. Cooperators also investigated factors that could contribute to infection and thus 

improve future release methods.

Gorse

Gorse (Ulex europaeus) is a spiny, woody, perennial that is extremely flammable, has fueled 

catastrophic fires around the world and in the United States, and has established in the 

northeastern United States from New York to Virginia and on the west coast from Washington to 

southern California. In FY23, APHIS cooperators concentrated on rearing, releasing, and 

confirming establishment of the gorse thrips, Sericothrips staphylinus, a biological control agent 

that was first introduced into the United States in 2020. In the past three years, cooperators have 

confirmed establishment of gorse thrips in the United States and have seen some minor impacts 

to the target, as the thrips populations slowly increase in size and density.

Hoary Cress

Hoary cress (Cardaria draba) is a long-lived and drought resistant perennial that spreads rapidly, 

occurs everywhere in the United States, except the southeast, forms dense monocultures that 
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displace native vegetation, contains chemicals that irritate the mucus membranes of grazing 

animals, and is difficult to control. This year, APHIS cooperators worked on rearing and 

releasing Aceria drabae, a mite that causes galls to form on the buds and developing flowers of 

hoary cress. Galls on the buds stunt plant growth, and galls on the flowers prevent seed 

production. Since the first release into the environment, which occurred in 2019, cooperators 

have shown that the mite can survive harsh winter conditions, like those that occur in Montana.

Houndstongue

Houndstongue (Cynoglossum officinale) is a shade-tolerant perennial that invades disturbed areas 

and outcompetes native vegetation in rangeland, pastureland, riparian areas, and on forest edges. 

The plant also causes issues when mixed with hay because it contains phytochemicals that cause 

liver disease and even liver failure in animals that consume too much of it. Its spiny seeds create 

problems for ranchers trying to market wool and fur as they must spend extra time and money 

removing these burs before selling the animal fiber. The burs are also known to damage 

livestock when they become lodged in the livestock’s eyelashes. Our investment, which began in 

FY22, helped APHIS cooperators map infestations, rank them in terms of suitability for releasing 

Mogulones borraginis, a weevil that feeds exclusively on the flowers and developing seeds of 

houndstongue, and release the weevil for the first time into the United States.

Puncturevine

APHIS provided a relatively small amount of funding (i.e., $15,000) in FY23 to investigate 

whether cold-hardy agents could enhance biological control of puncturevine (Tribulus terrestris). 

In the early 1960s, USDA invested in establishing two agents, Microlarinus lareynii, a seed 

weevil, and M. lypriformis, a stem weevil, to help control puncturevine, a plant present in nearly 

every state that when allowed to grow unchecked forms dense mats that create dangerous 

conditions for livestock, people, and pets. The project is often cited as a partial success because 

these weevils control puncturevine in some areas of the United States, but there are areas of the 

United States where these agents have never established. Redistributing these weevils from 

healthy, existing populations to climatically matched areas where they have never established 

may, therefore, enhance past investments in puncturevine biological control.

Yellow Starthistle

Yellow starthistle (Centaurea solstitialis) is an annual forb present in almost every state that 

forms dense monocultures, displaces native vegetation, reduces biodiversity, reduces the value of 

range and pastureland, and is toxic to horses. In FY23, APHIS cooperators focused on rearing, 

releasing, and monitoring for the establishment of Ceratapion basicorne, a weevil whose larvae 

feed and develop in the root crown of yellow starthistle. Our investment, which began in FY21, 

supported the first release of this weevil in 2020 and helped improve mass rearing techniques.
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Yellow Toadflax

Yellow toadflax (Linaria vulgaris) is a short-lived and drought resistant perennial that occurs 

almost everywhere in the United States. Yellow toadflax, like most invasive plants, can spread 

rapidly, form dense monocultures, displace native vegetation, and reduce the value of range and 

pastureland, as cattle generally avoid eating it. In FY23, APHIS cooperators concentrated on 

rearing, releasing, and confirming establishment of Rhinusa pilosa, a weevil that cooperators 

first released in Montana in 2019, Oregon and South Dakota in 2021, and Idaho and Wyoming in 

2022. While it is too early to claim that the weevil has established from most of these releases, 

the probability of establishment in South Dakota is high, and establishment is confirmed at 

multiple sites in Montana where the larvae are inducing galls on the stems of yellow toadflax. 

These galls ultimately stunt plant growth, reduce the number of rhizomes, and reduce seed 

production.

Science and Technology

Key Research by Target Species

In FY23 the program supported the coordination of research projects against 33 targets. 

Scientific research is focused on advancing research and data collection to support US permitting 

of 19 potential agents and on advancing methods development for rearing and release of 24 

agents. Below we highlight a handful of PPQ S&T led projects.

Asian Bean Thrips

The Asian bean thrips (Megalurothrips usitatus) is a recently established thrips pest of legumes 

affecting production of snap bean and other legume crops in south Florida. PPQ S&T and

University of Florida-Gulf Coast Research and Education Center sampled multiple legume fields 

and identified associated predators. Overall, sampling revealed a low number of predators under 

commercial snap bean production conditions. They consisted primarily of Orius spp. and 

Neoseiulus predatory mites. A yearlong study of flowers collected from lablab beans, a perineal 

specialty crop, showed that the predatory mites were always present within the flowers along 

with the pest. In addition, the group evaluated commercially available predators under laboratory 

conditions revealing that Amblyseius swirskii and A. cucumeris caused up to 80% mortality of 

the first instar larvae within 48 hours. 

Bemisia tabaci, Tuta absoluta

PPQ S&T, University of Florida Immokalee, and Instituto Valenciano de Investigaciones 

Agrarias (IVIA), Spain scientists co-authored a paper describing the results of a 4-year study that 

tested the ability of one established and one native omnivorous plant bugs’ (mirids; Nesidiocoris 

tenuis and Macrolophus praeclarus) ability to control whiteflies and their ability to persist in 
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open field tomato production. The group showed the predatory mirids control whiteflies but 

would leave the field once they consumed all the prey. Intercropping a few sesame plants 

provided a way to retain the mirids in the absence of prey. This study provides a method to use 

mirids as biological control agents in open-field tomato production to help manage existing and 

future invasive pests of tomato such as Tuta absoluta and Helicoverpa armigera. The publication 

is available at https://doi.org/10.3390/plants11202779

Brazilian Peppertree

In FY23, PPQ S&T began a comprehensive field monitoring initiative, covering 13 locations in 

Hidalgo County, five in Willacy County, and eight in Cameron County, Texas. This program 

aims to establish pre-release population data, to assess impact and the persistence of Thrips, 

(Pseudophilothrips ichini) releases to control Brazilian Peppertree. PPQ S&T has established a 

colony of P. ichini, and the first release occurred in Hidalgo County where PPQ S&T released a 

total of 10,500 Thrips. Parallel projects are also underway by ARS for release in Florida.

Brevipalpus yothersi

In response to the emergence of the citrus leprosis virus, CiLV-C2H, which affects ornamental 

crops such as hibiscus, PPQ and University of Florida-Tropical Research and Education Center 

conducted studies to test the role of biological control in the management of viruliferous 

Brevipalpus mites. Brevipalpus-transmitted viruses are spread by the feeding and movement of 

viruliferous B. yothersi within and among affected plants. The group found the predatory mite, 

Amblyseius largoensis, to be a promising biological control agent of B. yothersi. The effects of 

acaricides used to control B. yothersi were also evaluated on this predator. Researchers also 

evaluated the commonly used acaricides like abamectin and spirodiclofen, highly effective in 

controlling B. yothersi, are only slightly harmful to A. largoensis. Under greenhouse conditions, 

a combination of predators and acaricide increased suppression of B. yothersi from one month to 

three months after treatment application when compared to acaricides alone. Combining 

predatory mites with acaricides shows promise in improving B. yothersi management. 

Phantasma scale

PPQ S&T and Florida Department of Agriculture and Consumer Services evaluated the impact 

of the Phantasma scale (Fiorinia phantasma) at the original detection sites in Miami-Dade 

County and developed a method to show that the scale was low to non-detectable on most palm 

species. Two palm species (canary palms and tahina palms) had moderate levels of infestation. 

The natural enemies known to attack the scale were present on all palm species and at all 

locations. This information will help identify susceptible palm species and the established 

biological control agents that could be augmented or conserved to control the scale in the 

landscape as the pest spreads to new areas. 
17

Roseau cane scale

PPQ S&T research efforts concentrate on identifying key parasitoids in the community of natural 

enemies on Roseau cane scale across Asia, focusing on species in the genus Aprostocetus. Using 

molecular analyses, PPQ S&T detected a high degree of genetic diversity, suggesting the 

presence of seven cryptic species within the Aprostocetus genus. One of these species, referred to 

as Aprostocetus sp. 7, was detected in autumn 2023 in Louisiana. PPQ S&T developed an 

Aprostocetus rearing protocol and successfully established Aprostocetus sp. 7 in colony. PPQ 

S&T has initiated host range testing and life history studies of Aprostocetus sp. 7 to estimate its 

role on Rosea cane scale in Louisiana.

Shot Hole Borer

PPQ S&T is continuing work to identify an effective biological control agent for shot hole borer

(Euwallacea fornicates). PPQ S&T successfully reared parasitoid wasps in the genus 

Phymastichus for at least seven generations under laboratory conditions. Methods development 

work is ongoing to increase parasitism rates in the laboratory. Also, three species of non-target 

ambrosia beetles are being tested under laboratory conditions for use in host specificity testing. 

To improve parasitoid rearing, PPQ S&T conducted experiments comparing shot hole borer 

colonization and reproduction in different host tree species. In Taiwan, cooperators began 

experiments testing the utility of sentinel logs to attract parasitoids in the field, as well as 

exclusion experiments to assess impact of parasitoids on field populations of shot hole borers in 

Taiwan. 

Pest Exclusion and Import Programs 

In FY23, Pest, Pathogen, and Biological Control Permitting (PPBP) Unit continued to review 

and process petitions for approval for the release of biological control agents. These petitions 

were submitted by stakeholders and are at different phases of the review and approval process. 

The following are highlights:

Four biological control agents were granted Findings of No Significant Impact (FONSI’s) for the 

National Environmental Policy Act (NEPA) environmental assessments between Oct 1, 2022,

and Oct 1, 2023. PPQ permitted the release of the Murakami strain of Aphalara itadori against 

giant, Japanese, and bohemian knotweeds throughout the contiguous United States in March 

2023. In April and May 2023, three biological control agents were approved specifically for 

release in Hawaii: the golden sombermark butterfly, Euselasia chrysippe, against Miconia, the 

flea beetle, Syphraea uberabensis, against cane Tibouchina, and the parasitoid Phymastichus 

coffea against the coffee berry borer. 

APHIS received three petitions for new agents in 2023. Callopistria exotica was petitioned as an 

agent against old-world climbing fern, an invasive weed in the Everglades. Two petitions were 

received targeting invasive insects: Apanteles opuntiarum against the cactus moth in the southern 

United States, and Aprostocetis nitens against the Erythrina gall wasp in Hawaii. These petitions 

have all been reviewed and recommended for release by the TAG for weeds and the Biocontrol 
18

Review Committee for insects. PPQ is preparing biological assessments and environmental 

assessments from these petitions to continue through the regulatory process.

Three biological assessments are under review by the U.S. Fish and Wildlife Service; the

biological assessments for Bagous nodulosus against flowering rush and Dichrorampha aeratana

against oxeye daisy are nearing completion, and the assessment for Euchryptorrhynchus brandti

for control of tree of heaven is in review. APHIS also received one Letter of Concurrence from 

the U.S. Fish and Wildlife Service in September 2023 for a biological assessment for 

Ceuthorhynchus scrobicollis against garlic mustard; the environmental assessment for this has 

been prepared and the Tribal review package is being prepared.

Tribal review or responses to tribal review are being worked on for four petitions. Two packages 

are being prepared for review Aceria salsolae against Russian thistle and Bagous nodulosus

against flowering rush (also mentioned above, FWS and Tribal reviews do not have to be 

sequential). There are two Tribal reviews for which responses to Tribal concerns are being 

developed, one for Aceria angustifolia against Russian olive and another for Mogulones 

borraginis against houndestongue.

Two additional petitions are on hold while additional data is collected. One of these for two 

agents against Chinese tallow is at the end of the process however, because of resistance from 

beekeepers a working group has been developed to determine the value of Chinese tallow to 

beekeepers and determine if the agents might cause any economic impact. The two agents affect 

seedlings and are unlikely to have any impact on mature trees of value to beekeepers. Lastly, 

there was a petition that was not recommended by the TAG for Ceutorhynchus cardariae against 

hoary cress; additional research was requested. The response from the petitioners was recently 

received and is currently under review by APHIS and the TAG chair.
19

Appendix A: FY23 Biological Control Target, Agent, and Stage of Project 

Development

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

INSECTS 

Asian Citrus Psyllid

Tamarixia radiata Y X X X

Bagrada bug

Gryon aetherium X N-W X

Brown 

Marmorated Stink 

Bug

Trissolcus japonicus X N-W X X

Coffee Berry Borer

Phymastichus 

coffea

Y-H X X

Box Tree Moth

On -going 

exploration

Cactus Moth

Apanteles 

opuntiarum

X X N

Emerald Ash Borer

Oobius agrili Y X X X X

Spathius agrili Y X X X X

Spathius galinae Y X X X X

Tetrastichus 

planipennisi

Y X X X X

Erythrina Gall Wasp

Aprostocetus nitens X N

Harrisia Cactus 

Mealybug

Anagyrus cachamai X N

Anagyrus 

lapachosus

X N

Invasive Shot Hole 

Borers

Phymastichus sp. X N X
20

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

Eucosmophorus sp.XNX

Japanese Beetle

Istocheta aldrichiYXXX

Tiphia vernalisYXXX

Ovavesicula 

popilliae

XX

Olive Psyllid

Psyllaephagus 

euphyllurae

YXX

Roseau Cane Scale

Aprostocetus sp.XN

Spotted Lantern Fly

Anastatus orientalisXN

Dryinus sinicusXN

Spotted Wing 

Drosophilia

Ganaspis 

brasiliensis

YXX

Russian Wheat 

Aphid

Aphelinus hordeiYXX

WEEDS

Air Potato

Lilioceris egenaYXX

Lilioceris cheniYXX

Brazilian 

Peppertree

Pseudophilothrips 

ichini

YXX

Calophya latiforcepsYX

Canada Thistle

Puccinia 

punctiformis

XY-RX

Cane Tibouchina

Syphraea 

uberabensis

Y-HXX

Cape Ivy
21

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

Parafreutreta 

regalis

Y

Secusio extensaY

Cheatgrass

N/A onoing 

exploration

Common Crupina

Ramularia crupinaeY-RXX

Common Reed

Archanara 

geminipunctata

XN

Chinese Tallow

Bikashi collaris (leaf 

beetle)

XN

Gadirtha fuscaXN

Dyer’s Woad

Ceutorhynchus 

peyerimhoffi

XN

Ceutorhynchus 

rusticus

XN

Field Bindweed

Melanagromyza 

albocilia

XN

Microsphecia 

brosiformis

XN

Flowering Rush

Bagous nodulosusXXN

Garlic Mustard

Ceutorhynchus 

constrictus

XN

Ceutrhynchus 

scrobicollis

XN

Giant Reed

Lasioptera donacisYX

Giant Salvinia

Cyrtobagous 

salviniae

YX

Gorse
22

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

Sericothrips 

staphylinus

YX

Hawkweeds

Aulacidea pilosellaeX

Aulacidea 

subterminalis

YXX

Cheilosia urbanaYX

Hoary Cress

Aceria drabaeYXX

Ceutorhynchus 

cardariae

XN

Houndstongue

Mogulones 

borraginis

XN

Mogulones cruciferXN

Hydrilla

Bagous hydrillaeYX

Hydrellia 

balciunasi& 

pakistanae

YX

Knapweed - Diffuse 

& Spotted

Cyphocleonus 

achates

YXXX

Knapweed -

Russian

Aulacidea 

acroptilonica

YX

Pseudorchestes 

sericeus

XN

Jaapiella ivannikoviYX

Knotweeds

Aphalara itadoriYX

Melaleuca

Lophodiplosis 

indentata

YX

Old World Climbing 

Fern
23

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

Callopistria exoticaXN

Neostromboceros 

albicomus

XN

Oxeye Daisy

Dichrorampha 

aeratana

XN

Perennial 

Pepperweed

Ceutorhynchus 

marginellus

XN

Puncturevine

Microlarinus 

lareynii

YXXXX

Microlarinus 

lypriformis

YXXXX

Rush Skeletonweed

Bradyrrhoa 

gilveollea

YX

Russian Olive

Aceria angustifoliaeXN

Russian Thistle

Aceria salsolaeXN

Uromyces salsolaeXN

Scotch Broom

Bruchidius villosusYX

Exapion fuscirostreYX

Leucoptera 

spartifoliella

YX

Starthistle - Yellow

Ceratapion 

basicorne

YXX

Swallow-wort

Hypena opulentaYXX

Miconia

Euselasia chrysippeY-HXX

Tree of heaven

Verticillium 

nonalfalfae

XN
24

TARGET PEST/BC 

Agent

Pre-Approval 

Testing

Permitting 

Review

Approved for 

Release

Methods 

Development

Rearing & 

Release

Field Coll. & 

RedistributePost-release 

Monitoring

Technology 

Transfer 

Eucryptorrhynchus 

brandti

X N

Toadflax -

Dalmation

Mecinus 

janthiniformis

Y X

Rhinusa linariae Y X X

Toadflax - Yellow

Mecinus heydeni X Y

Mecinus janthinus Y X

Rhinusa pilosa Y X X

Tropical Soda Apple

Gratiana boliviana Y

Water Lettuce

Neohydronomus 

affinis

Y X X X X

Water Hyacinth

Megamelus 

scutellaris

Y X X X X

Neochetina spp. Y X X X X

X= Current stage of support, Y= Yes, N= No, Y-H= Yes - Hawaii only, Y-R= Yes - Research 

only, N-W = not approved for interstate release -within State movement only
25

Appendix B: FY23 PPA 7721-funded biological control projects.

State Project Title

FL Laurel Wilt Disease Biological Control

FL

Evaluating predatory plant bugs (Miridae) for biological control against the invasive South 

American tomato leafminer

MD Regional to National Post-Release Evaluation of Emerald Ash Borer Biological Control

FL Establishment and evaluation of Brazilian peppertree biological control

HI Field testing of bait stations containing a fungal pathogen to control invasive fruit flies

DE

Protection of North American ash against emerald ash borer with biological control: Measuring 

Natural Enemy Impacts

NH

Advancing blueberry plant protection: creating identification and monitoring tools for 

parasitoids of blueberry gall mid

FL Biological Control of Cactus Moth, Cactoblastis cactorum (Berg)

TX Biological Control of Brazilian Peppertree in the United States FY2023

HI

Systems Approach for the Management of Coffee Berry Borer in Hawaii and Puerto Rico with 

Emphasis on Biological Control

FL

Investigating interactions between multiple biocontrol agents used to control the invasive plant 

air potato

MD

Field Release and Evaluation of Ramularia crupinae for the Management of Noxious Crupina 

vulgaris Populations

KY The Japanese beetle control near airports and cargo transportation facilities: Field Testing

MA Developing biological control methods for Roseau cane scale

ID Nez Perce Tribe Bio-control Project-Noxious/Invasive Weed Survey and Control

FL Establishment and Evaluation of Air Potato Biological Control

NC Establishing and Assessing Biological Control Agents of Emerald Ash Borer in North Carolina

MA Classical Biological Control of Boxtree Moth

CA Biological Control of Bagrada Bug

HI

Management of hala scale in Hawaii, and survey of its potential biological control agents in its 

native range

TN

Post-Release Aftermath Assessment of Biological Control of Emerald Ash Borer in a Southern 

Climate (Tennessee)

DE Preemptive biological control of a high-risk invasive longhorn beetle

OR Deploying a Rapid Response Biocontrol Strategy against Emerald Ash Borer in Oregon

OR Biological Control of Spotted Wing Drosophila in Oregon

FL Registration of Verticillium nonalfalfae to control tree-of-heaven