Basics on Aquatic Biological Control Aquatic Weed Control-Short Course Coral Springs, Florida, May 2-5, 2016 Rodrigo Diaz Department of Entomology, LSU AgCenter
Goal: Explain how biological control works and how it has been used for aquatic weed management 1. What is biological control? 2. What steps are involved in biological control program? 3. How we select biological control agents? 4. Who regulates biological control in United States? 5. What is the history and safety of biological control? 6. Examples of aquatic weed biological control
What is Biological Control? Classical biological control-intentional introduction of agents from the weed s native range to reduce populations in the introduced range. Agents are released with the expectation of establishment and spread to achieve long-term control Biological control agents are host-specific insect herbivores, mites or plant pathogens that have coexisted with their host plant (target weed)
Biological control agents are monophagous Types of host specificity: Monophagous: feeding on one plant species or one genus Oligophagous: feeding on species in the same family Polyphagous: feeding on species of different families Price et al. 2011
Enemy Release Hypothesis (ERH) Native range Introduced range Biological control
Evolution of increase competitive ability (EICA) Native range Introduced range In the absence of natural enemies, plant reallocate resources from defense to growth and reproduction increasing its competitive ability Blossey and Notzold 1995
What is the ideal case in a biological control program? Abundance 1400 1200 1000 800 600 400 200 Weed Agent v v v Equilibrium 0 0 5 10 15 20 25 Time
How we can measure the success of a biological control program? Hoffmann s definitions: 1. Complete: no other control method is required 2. Substantial: other methods are needed but reduced efforts 3. Negligible: control dependent on other control measures Weed biological control programs: 60% agents established 50% resulted in some level of control Economic benefits: cost ratios range from 7:1 to 36:1 Different levels of success (Delfosse 2004): 1. Biological: measure of management of the target weed 2. Ecological: sustainable, low-input, and energy-conserving management 3. Economical: calculate benefit-cost ratios 4. Social: individuals across society 5. Legal: laws and regulations that facilitates biological control 6. Scientific: Knowledge gain of ecological systems under study 7. Political: long-term and increasing support for biological control
1. Theory and definitions 2. Steps in biological control of weeds
Steps during a biological control of program Pipeline 1. Select target weed 2. Surveys/Research in native range 3. Quarantine (host range tests) 4. Field releases/ Establishment 5. Technology transfer 5 to 10 years to complete
1. Select target weed Which other methods of control are available? Cost-benefit analysis of using biological control Has this weed been a target for biological control elsewhere? Are there any conflict of interests? Species identification and area of origin of the target weed
2. Surveys and research in the native range Foreign explorations in the weed s native range Surveys and collections of natural enemies Studies on the ecology of the weed and natural enemies in the native range Field host range of potential agents
3. Quarantine Import insects to quarantine using appropriate permits and labels Establish insect colonies in quarantine Studies on biology and impact of potential agents Conduct host range testing (specificity!)
4. Field releases and establishment Mass rearing of biological control agents Select field sites and method for releases Initiate field releases, monitor establishment and spread Evaluate impact of agents in the field: 1. Before and after 2. Exclusion using cages or insecticides 3. Long-term studies evaluating reduction of weed populations
5. Technology transfer Tropical soda apple (Solanum viarum) weed of pastures in FL Leaf beetle Gratiana boliviana released in 2003 Scientists Cattle ranchers Extension agents
5. Technology transfer
1. Theory and definitions 2. Steps in biological control of weeds 3. Selection of biological control agents (host specificity!)
Things to consider during agent selection Host specificity and risks to non-target species Adaptation to plant genotypes (DNA studies) Climate match between origin and introduced range (e.g. CLIMEX) Impact to target weed (e.g. reduced growth and reproduction) How many biological control agents should be released
Host range testing: Centrifugal Phylogenetic Method Test plant list: close related native species, economic importance, and threatened or endangered species Target weed Other species, same subgenus Other subgenus, same genus Other genus, same tribe Other tribe, same family Plants of economic importance
Host range testing critical step 1. No-choice tests: larval development / adult oviposition YES 2. Multiple-choice tests: agent preference 3. Open field tests YES
Risks to non-targets Direct effects Plants that are close related to the target weed have higher risks of non-target effects (similar chemistry, etc.) Example: The weevil Rhinocyllus conicus released against exotic Carduus thistles in the US in 1969. BUT the weevil attacked native Circium thistles in 1980s http://www.forestryimages.org Plants from the same tribe: Cynareae Feeding on native thistles was consistent with host specificity testing But there was a lack of concern over non-economic native species
Risks to non-targets Unintended effects Cactoblastis cactorum was released in Caribbean (Nevis) in 1957 and was first reported in Key West, FL in 1989 Pear prickly cacti in FL http://www.floridainvasives.org/heartland/links/cactoblastusmothheatherjezorekusf.pdf
Risks to non-targets Indirect effects Leaf feeding beetle Diorhabda carinulata (= D. elongate) released in 1999 against saltcedar (tamarix spp.) in Nevada and Utah Endangered bird the southwestern willow flycatcher used saltcedar for nesting in western riparian ecosystems http://www.fws.gov/utahfieldoffice/swfl.html http://fcwp.org/biocontrol/saltcedar.html DeLoach et al. 2004, Dudley and Bean 2012
Host-plant genotypes Brazilian peppertree Schinus terebinthifolia is an invasive species in FL. Genetic studies determined that two haplotypes (A, B) has been introduced in Florida. Introduced range: Florida Native Range: Brazil West coast (A) East coast (B) Hybrids A, B C-D A A A L M B-K Pseudophilothrips gandolfoi: poor performance on FL types Pseudophilothrips ichini: good performance on FL types Williams et al. 2005, 2007; Manrique et al.
Climate match Successful biological control of water hyacinth (Eichhornia crassipes) in East Africa, Argentina, Australia, USA, India, Thailand (tropical or subtropical areas). But this did not occurred in South Africa. Worst infestations found in the Highveld: high-altitude, extreme winter temperatures Water hyacinth http://www.bonniesplants.com/floating_plants/water_hyacinths Neochetina eichhorniae Insect densities remained low or failed to persist in the Highveld. In addition, eutrophic waters with high nutrient levels allow plants to recover Julien et al. 2000
Single vs. multiple biological control agents Lottery model: multiple agents are released to increase likelihood of success Silver bullet: a single agent capable of reducing pest populations Cumulative stress hypothesis: multiple agents are released to exert sufficient damage to the target weed Harris 1981, Myers 1985
1. Theory and definitions 2. Steps in biological control of weeds 3. Selection of biological control agents 4. Regulations and permitting process in USA
Petition for field releases Format of Petition Target weed information Biological control agent information Experimental methodology and analysis Results and discussion (host range tests) Protocol for releasing the agent TAG Committee: Technical Advisory Group (1987) Independent assessment of the safety of biological control agents. Composed by 15 governmental agencies from USA, Canada, and Mexico. Post-release monitoring Benefit/Risk Potential Environmental Impacts Petitioner s Conclusion Coombs et al. 2004
1. Theory and definitions 2. Steps in biological control of weeds 3. Selection of biological control agents 4. Regulations and permitting process in the USA 5. History and safety of weed biological control
History Early successes First successful biological control program of weeds (Australia) Cactoblastis cactorum from Argentina was introduced against prickly pear species (Opuntia spp.) in Australia http://en.wikipedia.org/wiki/cactoblastis_cactorum Julien and Griffiths 1998
History Early Successes 1930s: First successful biological control of weeds in USA Leaf beetle Crysolina quadrigemina against St John s wort (Hypericum perforatum) in California http://www.parfaitimage.com/insecta/chrysolina_quadrigemina.html Julien and Griffiths 1998
History Lessons learned during the last 100 years Improved protocols of host range testing Close relatives have higher risks of non-target effects Importance of selecting effective agents Risk-benefit-cost analysis Long-term post-release evaluations of biocontrol programs
Safety of biological control of weeds Precautionary Principle (1992) International code of best practices for Classical biological control of weeds (Balciunas 2000) Independent TAG committee (1987) Government Regulations/Permitting by USDA-APHIS-PPQ Outstanding record of safety: 133 weed species targeted, >350 biological control agents introduced, only 8 agents damaging non-target spp. but none at population levels Julien and Griffiths 1998, Waterhouse 1999
Summary of how biological control works Classical Biological Control is the intentional release of host-specific natural enemies to reduce weed populations Host specificity testing is critical during agent selection Climate match, genotype adaptations, and impact on the target weed USDA-APHIS-PPQ regulates biological control introduction Risk-benefit-cost analysis should be central for the release of agent Weed biological control has a long history of safety and success
Examples of classical biological control of aquatic weeds
What factors might influence the success of biological control program in aquatic systems? Connectivity Plant quality: Fertilizer Hydroperiod Use or disturbance
Alligatorweed (Alternanthera philoxeroides) Amaranthaceae Native range: Eastern coast of South America Exotic range: SE USA including Florida, Alabama, Georgia, Louisiana Heavy infestations disrupt water flow and large mats can float against bridges and dams. Hinders boat traffic and fishing.
Alligatorweed flea beetle (Agasicles hygrophila) Coleoptera: Chrysomelidae Native range: South America Destructive stages: Larval and adult Site of attack: Primarily leaves, stems
Impact: Massive defoliation during heavy attack, leading to submergence of floating mat Successful control by the flea beetle in Florida stimulated programs on water hyacinth and other aquatic weeds
Hydrilla (Hydrilla verticillata) Hydrocharitaceae Native range: Africa, Australia, Asia Exotic range: SE USA Currently spreading north. Invades all types of water bodies, tolerant of acidic, highly calcareous and brackish water. Cold climate does not seem to be a limiting factor.
Indian hydrilla leaf-mining fly (Hydrellia pakistanae) Diptera: Ephydridae Native range: Pakistan to China Destructive stages: Larval Site of attack: Leaves
Impact: Leaves with mines decay and at heavy infestations stems become necrotic Reduces photosynthetic ability and tuber numbers, eventually causing the plant to sink First introduced in the United States: 1987, in Florida. Established in: Alabama, Arkansas, Florida, Georgia, Louisiana, Texas.
Giant salvinia (Salvinia molesta) Salviniaceae Native range: Southeastern Brazil Exotic range: Louisiana, Texas with some minor infestations in south eastern USA Forms thick mats. Blocks drains, irrigation systems, carries insects such as mosquitoes, reduces oxygen, displaces native plants.
Salvinia weevil (Cyrtobagous salviniae) Coleoptera: Curculionidae Native range: South America Destructive stages: Larval and to lesser extent adult. Site of attack: Buds and rhizomes.
Impact: Plants turn brown, eventually sink Drastic results in several countries, ex. South Louisiana First introduced into the US in 2001. Successful control in southern Louisiana
Eurasian watermilfoil (Myriophyllum spicatum) Haloragaceae Native range: Africa and Eurasia Exotic range: 37 states including Alaska and Florida Natural lakes, rivers, brackish coastal waters. No apparent climate limit except USDA Zone 1 and 2 in north and 10 and 11 in south.
Watermilfoil moth (Acentria ephemerella) Lepidoptera: Pyralidae Native range: Europe Destructive stages: Larval Site of attack: Stems and leaves
Impact: Girdles leaves and stems during feeding, leaves and stems drop off plant Larvae feed on a variety of non-target plant species but does not cause similar damage to non-target plants in field studies Established in Iowa, Massachusetts, Michigan, Minnesota, New Hampshire, New York, Vermont and Wisconsin.
West Indian marsh grass (Hymenachne amplexicaulis), Poaceae Native range: South America and the West Indies Exotic range: Florida Invades wetland marshes and flood plains, drastic changes in hydroperiod, large biomass accumulation
Myakka bug (Ischnodemus variegatus) Hemiptera: Blissidae Native range: South America Destructive stages: nymphs, adults Site of attack: sap feeder
Impact: At heavy infestations causes leaf damage and stunted growth
Smooth cordgrass (Spartina alterniflora) Poaceae Native range: Atlantic and Gulf coasts of North America Exotic range: California and Washington Changes vegetation type of infected areas, displaces native plants and animals
Delphacid bug (Prokelisia marginata) Hemiptera: Delphacidae Native range: Atlantic and gulf coasts of North America. Destructive stages: Nymph and adult Site of attack: Leaves, sap-feeder
Impact: reduction in biomass, mortality Cage studies conducted in Willapa Bay, Washington
Waterhyacinth (Eichhornia crassipes) Pontederiaceae Native range: Tropical South America Exotic range: California, Florida, Hawaii, Louisiana, Texas, Puerto Rico Creates mats, changes vegetation type, prevents navigation, clogs pumps, intensify mosquito problems, reduces oxygen and photosynthesis for native plants
Waterhyacinth weevils (Neochetina spp.) Coleoptera: Curculionidae Native range: South America Destructive stages: Larvae, adults Site of attack: Leaves and lateral buds
Impact: Reduces photosynthetic area, causes desiccation, might sink mats
Waterlettuce (Pistia stratiotes) Araceae Native range: Africa, Asia and South America Exotic range: Subtropical Florida, Gulf Coast states, California Forms mats, depletes oxygen, causes thermal stratification, increases mosquito problems.
Waterlettuce weevil (Neohydronomus affinis) Coleoptera: Curculionidae Native range: South America Destructive stages: Larval and adult Site of attack: Leaves and shoots.
Impact: Stressed plants due to weevil damage are smaller and have fewer leaves, destruction of buoyancy
Summary on aquatic weed biological control - Biological control could help on reducing the inputs of herbicides into the watersheds. - Watershed connectivity, water-plant quality (fertilizer, pesticides), hydroperiod and disturbance might affect the outcome of the program. - Programs developed for emergent, floating and submersed aquatic weeds. - Biological control agents have remarkable adaptations to the aquatic environment. - Impacts of agents measured at different scales ranging from reduction leaf damage, defoliation to reduction of biomass. Thanks for your attention!