1. Insect biology and host range: risk assessment in biological control
J-R Baars
BioControl Research Unit
School of Biology and Environmental Science
University College Dublin

3. Natural Enemies Species: Pyrrhalta nymphaeae
Common name: Waterlily leaf beetle
Order: Coleoptera
Family: Chrysomelidae
Life History: Egg batches 6-20
3 Larval instars
10 eggs/day
Larva-Adult days
Damage High leaf turnover
5-17%  net primary production
Plant Hosts
Spatterdock, Nuphar advena (L.) Sibth. & Sm. (Nymphaeaceae)
Waterlilies, Nymphaea spp. (Nymphaeaceae)
Smartweed, Polygonum hydropiperoides Michx. (Polygonaceae)
Smartweed, Polygonum amphibium L. (Polygonaceae)
Bog myrtle, Myrica gale L. (Myricaceae)
Water shield, Brasenia schreberi J.F. Gmel. (Cabombaceae)
Arrowheads, Sagittaria sp. (Alismataceae)
Willows, Salix sp. (Salicaceae)
Water chestnut, Trapa natans L. (Trapaceae)

4. Top down control

5. Framework for Weed BC Target weed ecology
Exploration for potential control agents
Evaluation of biological control potential
Host specificity testing
Agent release and redistribution
Agent evaluation
Briese DT 2000 Classical Biological Control. In: Australian Weed Management Systems (ed. B Sindel) pp l

6. Target Weed Ecology Lagarosiphon major Submerged aquatic weed
Vegetative growth
Spread by fragmentation & layering
Top 75cm of submerged shoots (50cm x 50cm) = 160m2 Leaf surface area
Complex ecology dependant on location

7. Exploration – Origin Identifying the native range of the weed
Locate evolutionary centres of origin – locate phytophage diversity
Searching areas best ecoclimatically matched
Characterise agent & weed populations using molecular markers

8. Exploration – Origin
Lagarosiphon is native to sub-Saharan Africa & Madagascar
9 species are described (Symoens & Triest, 1983)
L. major native to southern Africa
Herbarium specimens held by SANBI
Altitude range: >2000m a.s.l

11. Exploration – Origin Shoot-tip borer Leaf-miner Leaf defoliator
Leaf Pathogen
Stem-borer

12. Agent selection criteria
Host specificity
Effectiveness
Process and release a large number of candidates to find successful agents
Prioritise by understanding the ecology of the weed-herbivore system, targeting specific parts of the weed’s life cycle
Two philosophies:

13. Life cycle: Hydrellia lagarosiphon
Adult
Eggs
Larva
Pupa
Widespread
Damaging
Short life cycle
Indications that it is host specific
Other similar ephydrids used as biocontrol agents

14. Ephydridae in Ireland ~29 species in the genus Hydrellia
~12 recorded in Ireland
Largest genus in the Hydrellinae
Little ecology known about the species
Exception include species of economic importance
e.g. Hydrellia griseola
Hydrellia lagarosiphon on L. major

15. Ephydrids as pests Hydrellia griseola, Smaller Rice Leaf Miner
Pest on wheat, barley, rice, maize, and timothy
Leaf mines causes reduction of plant photosynthesis intensity and of crop yield
14-16% damage to leaf surface, rice yields decrease by 6-9%
Populations regulated by parasitic wasps

16. Ephydrids as BC agents 2 species released in US ~ Hydrellia pakistanae
~ H. balciunasi
Target species Hydrilla verticillata
Originate from Asia and Australasia
Released in Southern US after host specificity testing
Balciunas et al 2002

17. Ephydrids as BC agents Leaf impact Released 1987
In early 2000s high populations were recorded
Low levels of leaf damage ~20% reduce photosynthesis

18. Ephydrids as BC agents Populations in US Taking ~18 yrs to build up
Deliberately released in 30 sites
Spread to sites km from release sites
Grodiwitz et al 2004

19. Ephydrids as BC agents Before
Fly impact damages Hydrilla infestations in Lake Seminole US
Monocultures replaced by mixture of species
After
Grodiwitz et al 2004

20. Evaluation of BC potential
Hydrellia lagarosiphon
1-11 larva in shoot tips in the country of origin
±50 leaves damaged/larva
Leaf damage increases with larval density
Carrying capacity suggests 3-4 larvae can be maintained per shoot tip

21. Evaluation of BC potential
Damage stimulates growth
Side shoots increase with herbivory
Shoot tip viability dependant on size and levels of larval damage
Shoot viability decreases with increasing larval density

22. Host specificity testing
Aims to predict the damage to nontarget species following release
Colonisation of nontarget species & temporary spill-over
The process has evolved over time as our understanding of host-plant interactions improve
An analytical process is followed to assess the potential risks
Ecology, behaviour and phylogeny
Determine the fundamental and realised host range

23. Host specificity testing
Fundamental host range
Absolute limits of a species host range
Independent of ecological setting
Realised host range
Variation in host acceptance following release
Spatial and temporal overlap of species

24. Risk assessment tools Test plant lists
Extensive list of plants selected using ‘Centrifugal phylogenetic method’ (Wapshere 1975)
~ a sequence of plants from those most closely related to the target weed to progressively more distantly related
Experimental tests
No-choice tests
Choice tests
Field tests

25. Test plant list Tanaka et al 1997
Tanaka et al The phylogeny of the family Hydrocharitaceae inferred

26. Phylogeny Classification proposed by Les et al 2006
Les et al A reappraisal of phylogenetic relationships in the monocotyledon family Hydrocharitaceae (Alismatidae) Aliso 22:

27. Proposed Classification
No native species in the subfamily Anacharidoideae
3 genera need consideration
~Hydrocharis
~Stratiotes
~Najas
Other alien species include Hydrilla & Vallisneria
Les et al 2006
Les et al A reappraisal of phylogenetic relationships in the monocotyledon family Hydrocharitaceae (Alismatidae) Aliso 22:

28. Related plants 3 genera need consideration ~Hydrocharis ~Stratiotes
~Najas

29. Host screening
Host range determined by larval stage

30. Host screening Behavioural constraints False +ves False -ves
(Heard 2000)
Heard, T.A., Concepts in insect host-plant selection behaviour and their application to host specificity testing.

31. Host screening Fecundity of adults dependant on temperature
Egg viability reduces through the life time of adult fly

32. Risk Assessment
The use of host specificity testing and field host- use studies to make pre-release relativity-based predictions of likelihood that the agents threaten nontarget plants
Test conditions designed for candidate agent evaluated
Host tests can predict the likelihood of nontarget attack
Retrospective assessments in the USA and Australia indicate that host testing procedures can predict field host host

33. Acknowledgements
Support by the following are kindly acknowledged

35. Hydrellia lagarosiphon
First discovered in 2008, IFI funded survey (Baars et al Hydrobiologia)
New species to science
Described by John Deeming (Wales Natural History Museum) (Deeming, 2011 –African Entomology)
Two additional populations maintained from collection trip in SA (May 2010)
Variation in the male genitalia
DNA analysis (barcoding)

36. Life+ project CAISIE
Survey Objectives
Collection trip to import known candidates (i.e. Bagous spp.)
Survey to establish the presence of additional candidates
Collection trip conducted in April-May 2010
Over 50 sites were visited, 18 with L. major

37. Shoot tip midge (Chironomidae)
Shoot-tip mining midge (cf. Polypedilum sp.)
Similar species found on other Hydrocharitaceae
Host-specificity in question
Taxonomy in question
Not easily reared under laboratory conditions

38. Leaf feeding moth (Lepidoptera)
Leaf feeding larvae (Nymphulinae, Paraponyx spp. & Synclita spp.)
Host specificity in question
USA call to consider Lepidopteran species to be considered for Hydrilla verticillata

39. Climate match native vs exotic
Different species persisting in different climatic areas, better pre-adapted?
Biotypes of species
Thermal tolerance
One of the main contributory factors to failure in weed biocontrol