Biological Control of Aquatic Weeds
Nathan E. Harms U.S. Army Engineer Research and Development Center, Vicksburg, MS
March 2014- ASWM Workshop
US Army Corps of Engineers
BUILDING STRONG® Why USACE?
BUILDING STRONG® http://plants.ifas.ufl.edu Characteristics . Most are exotic . Disturbance specialists ► r-strategists ► For example - Hydrilla • Rapid growth rates • Broad tolerance ranges • Early maturation and reproduction (fragmentation) • Dispersal adaptations (fragmentation) • Long-term survival (tubers) . Often favorable environmental conditions ► Space ► Nutrition ► Lack of natural enemies
BUILDING STRONG® Underlying Factors- Biological
. Most problem species are non-native . Introduced with no competent herbivores and diseases ►“Natural enemies”
BUILDING STRONG® Hydrilla verticillata – U.S.
No damaging herbivores/ pathogens
BUILDING STRONG® Hydrilla verticillata – China
>110 Herbivore/pathogen species
BUILDING STRONG® What is Biocontrol?
Introduction, by man, of parasitoids, predators, and/or pathogenic microorganisms to populations of plant or animal pests.
BUILDING STRONG® Biological Control Two Approaches
• Classical Biological Control
• Inundative Biological Control
BUILDING STRONG® Classical Biological Control Important Aspects . Host-Specific Agents (insects) ► target exotic plants . Release small numbers ► Population increase ► Expansion in distribution . Suppression is Key ► Long-term process ► Stress the target ► Bring into lowered equilibrium
BUILDING STRONG® Inundative Biological Control . Agents may not be Host- Specific ► ‘Bioherbicide’ . Release Large Numbers of Agents ► Population increase ► Creates Disease Levels . Mode of action ► Overwhelms Target ► Agents not self- sustaining . Not commonly used
BUILDING STRONG® Biological control . Minimize invasive characteristics/decrease competitive advantage . For example: ► Waterhyacinth weevils • Smaller height • Decreased flowering – less seeds • Less productivity ► Purple loosestrife agents • Reduced shoot/root growth • Fails to produce seeds
BUILDING STRONG® Challenges . How to define success ► Establishment ► Range Expansion agents ► Population Increase ► Impact • Change in species diversity/abundance • Biomass Decrease plants • Propagule Decrease ► Economic • Short/long term benefits . Long-term large scale monitoring needed ► Agent-caused declines? . Need demonstration projects . Hybrids!
BUILDING STRONG® Example: ‘Successional’ history of Caddo Lake, Texas
Waterhyacinth
American lotus
Brazilian elodea
Eurasian Giant watermilfoil salvinia
Hydrilla
BUILDING STRONG® BUILDING STRONG® Overseas research since 1990’s
BUILDING STRONG® Petitioner: • Consults with USFWS • Prepares petition for release or test plant list USDA-APHIS • Sends to APHIS-PPQ
TAG Executive Secretary: TAG • Establishes timelines • Sends petition to TAG members procedure TAG Members: • Review and Evaluate • Synthesize comments from subject matter experts Subject matter experts evaluate • Submit comments and recommendations
TAG Executive Secretary: • Logs and files comments and recommendations • Sends to Chair TAG petitioner: • Conducts more TAG Chair: research and • Consolidates recommendations • Resubmits petition or • Submits TAG recommendations to APHIS-PPQ, test plant list Petitioner, and others • Discontinues effort No • Or submits application Does TAG recommend release? to APHIS anyway Yes Petitioner submits application to APHIS-PPQ
BUILDING STRONG® Technical Advisory Group - TAG Make Recommendations Only
► Bureau of Land Management ► USDA, ARS ► Bureau of Reclamation ► USDA, APHIS ► Bureau of Indian Affairs ► USDA, NIFA ► Fish and Wildlife ► Forest Service ► National Park Service ► Documentation Center ► National Biological Survey ► Corps of Engineers ► Environmental Protection ► Weed Science Society Agency ► National Plant Board ► Representative for Canada ► Representative for Mexico
BUILDING STRONG® Plants and Their Agents
BUILDING STRONG® Alternanthera philoxeroides (Mart.) Griseb. (Alligatorweed)
► 1st Aquatic Biocontrol success ► Three agents released (1964-1971) • Agasicles hygrophila (Alligatorweed Flea Beetle) • Arcola malloi (Alligatorweed Stem Borer) • Amynothrips andersoni (Alligatorweed Thrips) ► Can be field-collected
BUILDING STRONG® Eichhornia crassipes (Mart.) Solms (Waterhyacinth)
Megamelus scutellaris (2010)
Neochetina eichhorniae "Mottled Waterhyacinth Weevil“ (1972)
. Acremonium zonatum . Alternaria eichhorniae . Cercospora piaropi . Uredo eichhorniae (rust) Neochetina bruchi Niphograpta albiguttalis “Chevroned Waterhyacinth Weevil” "Waterhyacinth Moth“ (1974) (1977)
BUILDING STRONG® >165,000 weevils released
BUILDING STRONG® Hydrilla verticillata (L.f.) Royle (Hydrilla)
•Four agents released since 1987 •Bagous affinis (1987) •Hydrellia pakistanae (1987) •Hydrellia balciunasi (1989) •Bagous hydrillae (1991) •Hydrellia spp. •Established •Larva Damaging Stage •Feeds on Internal Leaf Tissues •Widespread U.S. Distribution •Operational •Current surveys in Northern China/ South Korea
BUILDING STRONG® 250 Hydrilla Only Current effect: F(1, 116)=.48237, p=.48874 Hydrilla + Natives Vertical bars denote 0.95 confidence intervals c 200
2 150 b
100 ab
a
TUBERS PER m PER TUBERS 50
0
-50
NO HERBIVORY HERBIVORYBUILDING STRONG® Salvinia molesta Mitchell (Giant Salvinia)
The image part with relationship ID rId7 was not found in the file.
• Cyrtobagous salviniae- “Salvinia Weevil” (1999) • Operational • Available from LAERF, TX Technology transfer- Knutson & Nachtrieb
BUILDING STRONG®
Giant salvinia in TX pond
BUILDING STRONG® Other Agents . Hydrilla (USACE, USDA-ARS, CSIRO, CAS) ► Exploratory surveys still ongoing . Eurasian watermilfoil (Enviroscience) ► Native milfoil weevil available commercially . Waterlettuce (USACE) ► One agent operational, one in quarantine . Purple Loosestrife ► Four agents released . Melaleuca (USDA-ARS) ► Four agents released in FL 1997-2008 ► Operational, two agents in quarantine . Arundo (giant reed; USDA-ARS) ► Two agents released in TX 2009-2011 ► Operational? One agent in quarantine . Phragmites (Cornell U, USACE) ► Four agents in quarantine
BUILDING STRONG® Take Home: . Biocontrol is a tool ►Shift the advantage away from the weed ►Should be combined with ecosystem management & restoration • Target the system, not just the plant! ►Evolving technology • Product of 50+ years aquatic plant management ►Long-Term • Realistic time-lines often 5-10 years
BUILDING STRONG® For more information: [email protected]
BUILDING STRONG®