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Northern Research Station
One Gifford Pinchot Drive
Madison, WI 53726
(608) 231-9318
(608) 231-9544 TTY/TDD

Hemlock Woolly Adelgid

Hemlock Woolly Adelgid Biocontrol Research in China

Research Issue

[composite image:] Lady beetle collectors at temple below collecting site in Lijiang, China.

Hemlock Woolly Adelgid (HWA) in Asia is assumed to be maintained below damaging levels by a combination of natural enemies and host resistance.  In contrast, in the eastern U.S., it is regulated mainly by weather and the negative density-dependent consequences of host deterioration.  Various government agencies including the U.S. Forest Service and universities including the University of Massachusetts, Virginia Polytechnic Institute and State University, and others in the U.S. want to conduct a cooperative classical biological control program for HWA with The Peoples Republic of China (P.R. China).  These agencies and institutions in the U.S. have established an HWA Foreign Exploration Planning Committee to coordinate among the various organizations as well as to identify quarantine facilities for rearing, host range testing, etc. of promising natural enemies. These U.S. organizations develop cooperative agreements, grants, and contracts with various Chinese counterparts including the State Forestry Administration, Chinese Academy of Agricultural Sciences, Chinese Academy of Sciences, and others.

Our Research

  • HWA Natural Enemy Adult Complex
  • HWA Phenology
  • Study feeding preference of HWA natural enemies
    • Determine if HWA is a suitable food or host for oviposition by the HWA natural enemies when given no other host (no choice test)
    • Determine if other non-target species are fed or oviposited on when given no other host (no choice test)
    • Measure predator preferences if both HWA and non-target species are presented (choice test)
  • Provide tentative identification of Laricobius, lady beetles, and other collected taxa.
  • Collect and ship promising natural enemy species to the United States for further evaluation. 

Expected Outcomes

  • Determine the potential for using natural enemies to lessen the impacts of HWA populations on Tsuga spp. in the eastern United States.

Research Results

HWA biocontrol research in Sichuan

Studies at three sites in Sichuan were made on the life cycle and the spatial and temporal distribution of HWA in hemlock crown. Natural enemies of HWA were also collected at each of the three sites an average of 1.5 times/ month. Nine new locations for collecting natural enemies were found. A total of 1,701 natural enemies were collected at the three primary sites and 2,200 specimens were collected at other sites. Feeding preference tests in the laboratory indicate that 17 species feed on HWA. Survey of new sites found that the range of Scymnus ningshanensis is much greater than previously known and that its climate range is the greatest of the Neopullus lady beetles previously exported to the United States. We also successfully reared Laricobius sp, Melyridae and Scymnus camptodromus on HWA. We were very successful in collecting of natural enemies for export to the U.S. and shipments made in spring and fall 2006 totaled 677 specimens of eight species of lady beetles. Many of these are new to us and we think that at least one is a promising new candidate for biological control.  More than 200 S. camptodromus were exported in spring 2007 to reestablish a colony.

HWA biocontrol research in Yunnan

Three sites in Yulong County, Yunnan were sampled monthly to determine the distribution of HWA and its natural enemies in space and time. The distribution of HWA in the canopy of hemlock was found to be greater in the lower portion (26.3 percent of branch tips infested) than in the upper portion (22.9 percent infested). More tips were infested on the north side (31.6 percent ) of the crown than the south, east, and west (27.8 percent , 20.8 percent , and 18.3 percent , respectively). The phenology of HWA life stages was monitored each month for one year. The egg stage of HWA was very abundant in January, February, and March and again in May and June, with a few eggs also in September. At two sites, HWA density increased during the spring and then decreased during late summer and fall. The most abundant species of predator in the umbrella-beating samples were Tetraphleps galchanoides during May and Scymnus camptodromus during the fall. The site that had the highest density of HWA in April and May also had the highest number of predators. Three shipments of seven species and 335 specimens of natural enemies were exported from Yunnan in 2006. More than 200 T. galchanoides were exported in spring 2007.

HWA biocontrol research in Beijing

More than 30 species of lady beetles collected in Sichuan and Yunnan Provinces were identified. The most important species were Scymnus (Neopullus) camptodromus, Scymnus (Neopullus) sinuanodulus, Scymnus (Neopullus) ningshanensis, Scymnus (Pullus) huashansong, Oenopia signatella (Mulsant), Oenopia deqenensis Jing, Scotoscymnus sp. prob. nov (=Scy 05 of Yunnan) and Scymnus (Neopullus) sp. prob. nov (Scy 35 of Sichuan). Based on what is known about the biology of related species and preliminary observations, the last three species are recommended for further study as potential biological controls. Three collecting trips were made in 2006 and one so far in 2007. In April, an expedition to Guizhou Province found very few HWA and no predators. In late May, we found very high density of HWA and the anthocorid, Tetraphleps galchanoides Ghauri and many other predators in Yunnan. A return to Yunnan in late July found many lady beetles including a new species that may be a good candidate (Scotosymnus sp.). A revisit to one site in May 2007 found fewer HWA, increased Ss and fewer Tg.  Some host range tests were done in the laboratory at Beijing using a colony of bean aphid. The lady beetle Oenopia signatella and T. galchanoides both feed on the bean aphid. We were able to rear O. signatella from egg to adult on bean aphid, although growth was not as good.  Altogether 13 species were tested with aphids in no-choice tests; only 4 species did not feed on bean aphid (Scymnus (Pullus) geminus, Sasajiscymnus heijia, Scotoscymnus sp., and Scymnus (Pullus) sp. (brown).  T. galchanoides fed voraciously on bean aphid and quickly molted to the next stage.

Li, Li; Lu, Wenhua; Montgomery, Michael; Van Driesche, Roy; Salom, Scott. 2007. Hemlock woolly adelgid and its natural enemies in Yunnan Province, China: first-year (2005) results.

Montgomery, Mike; Van Driesche, Roy; Salom, Scott; Lu, Wenhua; Yu, Guoyue; Zhou, Jianhua; Li, Li; Shiyake, Shigehiko. 2007. Enhancement of foreign collection and quarantine evaluation of hemlock woolly adelgid natural enemies.

Zhou, Jianhua; Xiao, Yinbo; Xiao, Yugui; Lu, Wenhua; Montgomery, Michael; Van Driesche, Roy; Salom, Scott. 2007. Hemlock woolly adelgid and its natural enemies in Sichuan Province, China, 2005

Montgomery, Michael; Wang, Hongbin; Butin, Elizabeth; Yao, Defu; Lu, Wenhau; Havill, Nathan. 2005. Scymnus Ningshanensis Yu Et Yao (Coleoptera: Coccinellidae) for biological control of Adelges tsugae (Homoptera: Adelgidae).

Butin, Elizabeth; Elkinton, Joseph; Havill, Nathan; Montgomery, Michael. 2003. Comparative impact of Scymnus ningshanensis and Pseudoscymnus tsugae (Coleoptera: Coccinellidae) on the hemlock woolly adelgid.

Montgomery, Michael E.; Yao, Defu; Wang, Hongbin. 2000. Chinese Coccinellidae for biological control of the hemlock woolly adelgid: description of native habitat.

Yu, Gouyue; Montgomery, Michael E.; Yao, Defu. 2000. Lady beetles (Coleoptera: Coccinellidae) from Chinese hemlocks infested with the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae). The Coleopterists Bulletin. 54(2): 154-199.

Research Participants

Principal Investigators

  • Jianhua Zhou, Sichuan Academy of Forestry, Chengdu, P. R. China
  • Li Li, Research Institute of Resource Insects, Chinese Academy of Forestry, Kunming, P. R. China
  • Guoyue Yu, Beijing Academy Agricriculture Forestry Sciences
  • Michael Montgomery, Research Entomologist, U.S. Forest Service, Northern Research Station

More Information

  • Melody Keena, Research Entomologist, U.S. Forest Service, Northern Research Station


Last Modified: 05/08/2015

About this Research Area

Science theme: Forest Disturbance Processes

Science Topic: Invasive Species

About Hemlock Woolly Adelgid
Biological Control
Featured Publication

Zhou, Jianhua; Xiao, Yinbo; Xiao, Yugui; Lu, Wenhua; Montgomery, Michael; Van Driesche, Roy; Salom, Scott. 2007. Hemlock woolly adelgid and its natural enemies in Sichuan Province, China, 2005