pp 1–10 | Cite as

Risk assessment to interpret the physiological host range of Hydrellia egeriae, a biocontrol agent for Egeria densa

  • Rosali SmithEmail author
  • Rosie Mangan
  • Julie A. Coetzee


Egeria densa Planchon (Hydrocharitaceae) is a submerged macrophyte native to South America. It forms part of a new suite of invasive aquatic plants that has benefited from open nutrient-rich freshwater systems following the successful biological control of floating aquatic plants in South Africa. The specificity of the leaf-mining fly, Hydrellia egeriae Rodrigues (Diptera: Ephydridae) was tested, using traditional laboratory host-specificity testing (i.e., no-choice and paired choice). Only one non-target species, Lagarosiphon major Deeming (Hydrocharitaceae) supported larval development during pair-choice tests. In order to avoid the rejection of a safe and potentially effective agent, continuation (i.e., multiple generations) tests were conducted to measure the ability of the non-target species to nutritionally support a population indefinitely. None of these species could sustain a viable agent population for more than three generations. Laboratory host-specificity tests are limited as they exempt certain insect-host behaviours. To enhance the interpretation of host-specificity results, a risk assessment was conducted using agent preference (i.e., choice tests) and performance (i.e., choice and continuation tests) results. The feeding and reproductive risk that H. egeriae poses to non-target species is below 2%. Based on these findings, permission for its release in South Africa has been obtained.


Submerged aquatic weed Ephydridae Continuation test Multiple generation test 



This research was funded through the Department of Environmental Affairs, Natural Resource Management Programme’s Working for Water programme. Further funding for this work was provided by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa. Thanks are extended to the editors and anonymous reviewers for their patient guidance and critical comments, which has improved the quality of this manuscript. Thanks are due to Dr Emily Strange, Dr Grant Martin and Dr Guillermo Cabrera Walsh for their assistance in this study.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. Balciunas JK, Burrows DW, Purcell MF (1996) Comparison of the physiological and realized host-ranges of a biological control agent from Australia for the control of the aquatic weed, Hydrilla verticillata. Biol Control 7:148–158CrossRefGoogle Scholar
  2. Briese DT (2003) The centrifugal phylogenetic method for selection of test plants for host-specificity testing of biological control agents: Can it and should it be modernized? In: Jacob HS, Briese DT (eds) Improving the selection, testing, and evaluation of weed biological control agents. CRC for Australian Weed Management, Glen Osmond, pp 23–33Google Scholar
  3. Briese DT (2005) Translating host-specificity test results into the real world: the need to harmonize the yin and yang of current testing procedure. Biol Control 35:208–214CrossRefGoogle Scholar
  4. Buckingham GR, Okrah EA (1993) Biological and host range studies with two species of Hydrellia (Diptera: Ephydridae) that feed on hydrilla, technical report A-93-7. U.S. Army Engineer Waterways Experiment Station, VicksburgGoogle Scholar
  5. Cabrera Walsh G, Ym Dalto, Mattioli FM, Carruthers RI, Anderson LW (2013) Biology and ecology of Brazilian elodea (Egeria densa) and its specific herbivore, Hydrellia sp., in Argentina. BioControl 58:133–147CrossRefGoogle Scholar
  6. Chen LY, Chen JM, Gituru RW, Wang QF (2012) Generic phylogeny, historical biogeography and character evolution of the cosmopolitan aquatic plant family Hydrocharitaceae. BMC Evol Biol 12(30):1–12Google Scholar
  7. Coetzee JA, Hill MP (2012) The role of eutrophication in the biological control of water hyacinth, Eichhornia crassipes, in South Africa. BioControl 57:247–261CrossRefGoogle Scholar
  8. Coetzee JA, Byrne M, Hill MP (2003) Failure of Eccritotarsus catarinensis, a biological control agent of waterhyacinth, to persist on pickerelweed, a non-target host in South Africa after forced establishment. Biol Control 28:229–236CrossRefGoogle Scholar
  9. Coetzee JA, Bownes A, Martin GD (2011) Prospects for the biological control of submerged macrophytes in South Africa. Afr Entomol 19(2):469–487CrossRefGoogle Scholar
  10. Cook CDK, Urmi-König K (1984) A revision of the genus Egeria (Hydrocharitaceae). Aquat Bot 19:73–96CrossRefGoogle Scholar
  11. Cruttwell McFadyen RE (2003) Does ecology help in the selection of biocontrol agents? In: Jacob HS, Briese DT (eds) Improving the selection, testing and evaluation of weed biological control agents. CRC for Australian Weed Management, Glen Osmond, pp 5–9Google Scholar
  12. Cullen JM (1990) Current problems in host-specificity screening. In: Delfosse ES (ed.) Proceedings of the VII international symposium on biological control of weeds, Instituto Sperimentale per la Patologia Vegetale (MAF), Rome, Italy, pp. 27–36Google Scholar
  13. Day MD, Riding N, Senaratne KADW (2016) The host specificity and climate suitability of the gall fly Cecidochares connexa (Diptera: Tephritidae), a potential biological control agent for Chromolaena odorata (Asteraceae) in Australia. Biocontrol Sci Technol 26(5):691–706CrossRefGoogle Scholar
  14. Deonier DL (1971) A systematic and ecological study of Nearctic Hydrellia (Diptera: Ephydridae). Smithson Contrib Zool 68:1–147CrossRefGoogle Scholar
  15. Futuyma DJ, Agrawal AA (2009) Macroevolution and the biological diversity of plants and herbivores. Proc Natl Acad Sci 106(43):18054–18061CrossRefGoogle Scholar
  16. Gettys LA, Haller WT, Petty DG (2014) Biology and control of aquatic plants, 3rd edn. Aquatic Ecosystem Restoration Foundation, Marietta, p 238Google Scholar
  17. Havill NP, Davis G, Mausel DL, Klein J, McDonald R, Jones C, Fischer M, Salom S, Caccone A (2012) Hybridization between a native and introduced predator of Adelgidae: an unintended result of classical biological control. Biol Control 63:359–369CrossRefGoogle Scholar
  18. Hinz HL, Winston RL, Schwarzländer M (2019) How safe is weed biological control? A global review of direct nontarget attack. Q Rev Biol 94(1):1–27CrossRefGoogle Scholar
  19. Hussner A, Stiers I, Verhofstad MJJM, Bakker ES, Grutters BMC, Haury J, van Valkenburg JLCH, Brundu G, Newman J, Clayton JS, Anderson LWJ, Hofstra D (2017) Management and control methods of invasive alien freshwater aquatic plants: a review. Aquat Bot 136:112–137CrossRefGoogle Scholar
  20. Louda SA, Pemberton RW, Johnson MT, Follett PA (2003) Non-target effects—the Achilles heel of biological control? Retrospective analysis to reduce risk associated with biocontrol introductions. Ann RevEntomol 48:365–396Google Scholar
  21. Marohasy J (1998) The design and interpretation of host-specificity tests for weed biological control with particular reference to insect behavior. Biocontrol News Inf 19:13–20Google Scholar
  22. Martin GD, Coetzee JA, Baars JR (2013) Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), a potential biological control agent for the submerged aquatic weed, Lagarosiphon major (Ridley) Moss (Hydrocharitaceae). Afr Entomol 21(1):151–160CrossRefGoogle Scholar
  23. Mphephu TE, Olckers T, Simelane DO (2017) The tortoise beetle Physonota maculiventris (Chrysomelidae: Cassidinae) is suitable for release against weedy Mexican sunflower Tithonia diversifolia (Asteraceae) in South Africa. Biocontrol Sci Technol 27(4):510–524CrossRefGoogle Scholar
  24. Olckers T (2000) Biology, host specificity and risk assessment of Gargaphia decoris, the first agent to be released in South Africa for the biological control of the invasive tree Solanum mauritianum. Biocontrol 45:373–388CrossRefGoogle Scholar
  25. Paynter Q, Fowler SV, Gourley AH, Peterson PG, Smith LA, Winks CJ (2015) Relative performance on test and target plants in laboratory tests predicts the risk of non-target attack in the field for arthropod weed biocontrol agents. Biol Control 80:133–142CrossRefGoogle Scholar
  26. Petersen G, Seberg O, Cuenca A, Stevenson DW, Thadeo M, Davis JI, Grahams D, Ross TG (2015) Phylogeny of the Alismatales (Monocotyledons) and the relationship of Acorus (Acorales?). Cladistics 32(2):1–19Google Scholar
  27. R Core Team (2014) R: a language and environment for statistical computing. R foundation for statistical computing, Vienna, Austria. Available via R Project:
  28. Sheppard AW, van Klinken RD, Heard TA (2005) Scientific advances in the analysis of direct risks of weed biological control agents to nontarget plants. Biol Control 35(3):215–226CrossRefGoogle Scholar
  29. Smart RM, Barko J (1985) Laboratory culture of submersed freshwater macrophytes on natural sediments. Aquat Bot 21:251–263CrossRefGoogle Scholar
  30. Tipping PW, Foley JR, Gettys LA, Minteer CA (2018) Assessing the risk of Eccritotarsus eichhorniae to pickerelweed, Pontederia cordata in North America. Biocontrol Sci Technol 28(4):299–308CrossRefGoogle Scholar
  31. van Driesche RG, Murray TJ (2004) Overview of testing schemes and designs used to estimate host ranges. In: van Driesche RG, Reardon R (eds) Assessing host ranges for parasitoids and predators used for classical biological control: a guide to best practice. USDA, Forest Health Technology Enterprise Team, Morgantown, pp 68–89Google Scholar
  32. Wan FH, Harris P (1997) Use of risk analysis for screening weed biocontrol agents: Altica carduorum guer. (Coleoptera: Chrysomelidae) from China as a biocontrol agent of Cirsium arvense (L.) Scop. in North America. Biocontrol Sci Technol 7:299–308CrossRefGoogle Scholar
  33. Wapshere AJ (1974) A strategy for evaluating the safety of organisms for biological weed control. Annu Appl Biol 77:201–211CrossRefGoogle Scholar
  34. Wheeler GS, Duncan JG, Wright S (2017) Predicting spillover risk to non-target plants pre-release: Bikasha collaris a potential biological control agent of Chinese tallowtree (Triadica sebifera). Biol Control 108:16–21CrossRefGoogle Scholar
  35. Yarrow M, Marín VH, Finlayson M, Tironi A, Delgado LE, Fischer F (2009) The ecology of Egeria densa Planchon (Lipliopsida: Alismatales): a wetland ecosystem engineer? Rev Chil Hist Nat 82:299–313CrossRefGoogle Scholar

Copyright information

© International Organization for Biological Control (IOBC) 2019

Authors and Affiliations

  1. 1.Centre for Biological ControlRhodes UniversityMakhandaSouth Africa
  2. 2.Biological and Environmental SciencesUniversity of StirlingStirlingUK

Personalised recommendations