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 herbivores, mites or plant pathogens that have co- existed 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?

1400 Weed 1200 Agent 1000

800 v v v 600

Abundance 400

200 Equilibrium

0 0 5 10 15 20 25 Time How we can measure the success of a biological control program?

Weed biological control programs: Hoffmann’s definitions: 60% agents established 1. Complete: no other control method is required 50% resulted in some level of 2. Substantial: other methods are needed but reduced efforts control 3. Negligible: control dependent on other control measures 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 2. Surveys /Research 3. Quarantine 4. Field releases/ 5. Technology weed in native range (host range tests) Establishment 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 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

Target weed Other species, same subgenus Test plant list: close related native Other subgenus, same genus species, economic importance, Other genus, same tribe and threatened or endangered Other tribe, same family species 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

• 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 http://www.forestryimages.org 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

B-K Pseudophilothrips gandolfoi: poor performance on FL types M West coast (A) A L East coast (B) C-D Hybrids A, B A A 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 Insect densities remained low or failed to persist in the Highveld. In addition, eutrophic waters with high Neochetina eichhorniae nutrient levels allow plants to recover http://www.bonniesplants.com/floating_plants/water_hyacinths 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 • Post-release monitoring Group (1987) • Benefit/Risk • Independent assessment of the safety • Potential Environmental Impacts of biological control agents. • Composed by 15 governmental • Petitioner’s Conclusion agencies from USA, Canada, and Coombs et al. 2004 Mexico. 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 ( variegatus) :

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 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!