Aquatic Invasive Weeds

Mark Sytsma Center for Lakes and Reservoirs

Aquatic Bioinvasion Research and Policy Institute Portland State University

Benton County CWMA Aquatic Applicator Short Workshop

Corvallis • 10 March 2016

Overview

Why manage invasive aquatic weeds? Some common and not-so-common invasive

species (focus on the Pacific Northwest) Options for aquatic plant management Some nonplant invasive species to watch for

Introduction Management of aquatic weeds is complicated

because: Many species are easily confused with native or legally

imported species Common names are confusing and often misapplied Many aquatic weeds reproduce vegetatively from small

fragments Water moves Aquatic systems contain many sensitive and endangered

iconic species that complicate management

Algae Microscopic

greens, diatoms, golden, dinoflagellates, cyanobacteria

Nitella Chara

Ecological impacts Reduce light penetration &

mixing Reduce species diversity Alter temperature, dissolved

oxygen & pH Degrade fish habitat Altered nutrient cycling can

lead to algae blooms and toxicity

Impacts on biodiversity

Madsen et al. 1991

Food web and nutrient cycling

Carpenter and Lodge 1986

Economic impacts Reduce flow in irrigation

canals and drainage ditches Increased cost of irrigation Flooding Clogged pumps & intake

structures Loss of recreational

resources Negative impacts on

property values

Human safety

Myriophyllum spicatum Eurasian watermilfoil

Feathery leaves divided into leaflets. 3 to 5 leaves grow in a whorled pattern around the stem.

When out of water, leaves lose their rigidity and collapse around the stem.

Easily confused with native milfoil species

Eurasian

watermilfoil Northern

watermilfoil

Myriophyllum spicatum x sibiricum Hybrid watermilfoil

Intermediate characteristics Rapidly spreading in Great Lakes

region Increased resistance to several

herbicides commonly used on EWM Confirmed in Howard Prairie

Reservoir & multiple sites along the Rogue River

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Myriophyllum heterophyllum variable leaf watermilfoil, two-leaf watermilfoil, & red foxtail

Siltcoos Lake, Oregon Present at 22 of 297 sampling

locations Extensive monocultures in protected

bays

Class A noxious weed in Washington 5 lakes being treated

Hydrilla verticillata Monecious biotype in Washington

(10yrs, $10M eradication) Dioecious biotype (only female)

thermally-influenced Bruneau River, Idaho Endangered snail present Diquat and handpulling

Hydrilla verticillata hydrilla, Florida elodea, water thyme

Egeria densa Brazilian elodea

Dioecious Only male plants outside native range in South

America Dispersal by fragments only Most common invasive aquatic plant in west-side lakes

Elodea canadensis/nutallii American waterweed, common elodea

Native species common throughout Oregon

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E. canadensis E. nutallii

Similarities in the Hydrocharitaceae U

SD

A P

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NT

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ata

base

Elodea

canadensis/nutallii

(native)

Egeria densa

(B-list noxious weed) Hydrilla verticillata

(A-list noxious weed)

Turions and tubers are features of hydrilla

Potamogeton crispus curly leaf pondweed

Common throughout Oregon Turions form in spring on small plants, sprout

in fall and overwinter Typically bimodal biomass curve – most

abundant in spring and fall, dies back in summer

Long-term control requires interrupting turion formation

Cabomba caroliniana

Appears to be restricted to low-pH, dystrophic (tea colored) lakes

Easily confused with submersed form of water buttercup (which has alternate leaves)

Ranunculus aquatilus

gobotany.newenglandw

ild.org

Ceratophyllum demersum coontail

Native Not rooted Bifurcated leaves Inconspicuous,

submersed flowers

Duckweeds

Mail-Tribune file photo

http://ww

w.ruduckweed.org/

duckweed

http://waynesword.palomar.edu/1wayindx.htm

Eichhornia crassipes water hyacinth

10 miles of thermally influenced Snake River infested eradicated

Umpqua River infestation

Salvinia molesta salvinia

Cryptobagous salviniae

Annual releases of Cryptobagous salviniae on Lower Colorado R.

Source: Dewey Murray, USDA APHIS PPQ

Efficacy of Cryptobagous salviniae on Lower Colorado R.

Photos: Dewey Murray, USDA APHIS PPQ

2004 2005

Limnobium laevigatum South American spongeplant

• Redding pond (June 2005) • 0.25 m2 quadrat: >2,000 plants • Chokes out water primrose and parrotfeather; grass growing on the mat • A-listed noxious weed in OR

Azolla pinnata feathered water fern

Federally listed noxious weed

Azolla filiculoides and A. mexicana

Natives

Nymphaea odorata fragrant water lily

Identification:

Rooted aquatic perennial Grows in depths of 3-6 feet Floating heart-shaped or

circular leaves (30 cm); purplish underneath, leathery, slit in one side

Large (6-12 cm) fragrant flowers; 20-30 petals, range of colors with yellow centers

Seed and rhizomes

Nymphoides peltata yellow floating heart

Native to East Asia A-listed noxious weed Scattered populations in

southern and eastern OR, and Portland metro areas

Bacopa rotundifolia disk water hyssop

Considered imperiled in neighboring states Herbarium specimen in WY from 1891and from ID in 1933

First occurrence in Oregon in Columbia River in 2014 Weedy in rice fields in CA What to do about it in Oregon?

Natureserve.org

Nuphar polysepala yellow pond-lily

NATIVE Similar habitat Larger, oval to heart-

shaped leaves with a prominent midvein

Flowers – yellow petals and centers, 9-petals

Brassenia schreberii watershield

NATIVE Similar

habitat Oval, peltate

leaves Inconspicous

flowers

Phalaris

arundinacea

Lythrum

salicaria

Iris

psuedacorus

Yellowflag Iris Purple loosestrife Reed canary grass

Cattails Typha latifolia

Native Typha angustifolia

Invasive X Typha glauca

hybrid

Phragmites australis reed

ssp. americanus ssp. australis

Sagittaria spp.

Sagittaria

graminea Class B in WA

(3 locations)

Sagittaria

platyphylla (1 lake in WA/

Blue Heron Wetland,

Portland

Potential noxious listing)

Sagittaria

rigida Class B in WA

(6 locations)

Myriophyllum aquaticum parrotfeather milfoil

Native to South America

Only female plants present

Dispersal by fragmentation

Difficult to control

Ludwigia spp. Water primrose water primrose

Abundant in middle reaches of the Willamette downstream to Columbia R.

Active control efforts underway Delta Ponds, Eugene Willamette (Willamette Riverkeepers)

Aquatic perennial Moving down Columbia River from infestation in Montana Large infestation in Yakima River Suction harvesting of small populations near McNary Dam Submersed and emergent growth forms Dispersal by rhizome fragments

Butomus umbellatus Flowering rush

Spartina spp. Estuarine cordgrasses

• 4 non-native, invasive species – S. alterniflora (Eastern & Gulf coast of North

America) – S. patens (Eastern & Gulf coast of North America) – S. anglica (hybrid of English S. maritima & S.

alterniflora) – S. densiflora (South America)

• 1 native (S. foliosa)in California • Hybrids

S. alterniflora

S. densiflora

S. patens

S. anglica

Known Spartina Distribution on the West Coast

Comox Harbor, BC Fanny Bay, BC Boundary Bay, BC Puget Sound, WA Gray’s Harbor, WA Willapa Bay, WA Columbia River Sand Lake, OR Siuslaw River, OR Coos Bay, OR Humboldt Bay, CA San Francisco Bay, CA

Aquatic Weed Control Methods

Biological Manual Physical Mechanical Chemical

Biological Control Options Purple loosestrife

Galerucella spp. (leaf feeding), Hylobius (root) & Nanophyes (flower/seed)

Very successful – reduction in growth, occurrence & competitiveness

Eurasian watermilfoil native weevil - Euhrychiopsis lecontei Results difficult to predict (fish predation,

overwintering habitat)

Grass Carp (Ctenopharyngodon idella) Generalist feeders – low/no selectivity Very limited applications “biological success” vs “impact success”

Manual Control Options

Hand-pulling, or underwater weeding Target specific weeds, move around

obstructions, minimal equipment Labor intensive, creates murky water

and fragments Rakes, cutters

Inexpensive Labor intensive, creates murky water

and fragments

Physical Control Options Benthic barriers

Sediment blanket that blocks light, compresses plants Controls rooted plants Expensive for large ponds Requires regular maintenance Interferes with bottom habitat Unruly to anchor in large ponds

Drawdown May be ineffective in wet conditions and without freezing Increase in some weeds (Potatmogeton, hydrilla)

Physical Control Options

Shading Aquatic dyes - preemergent,

depths > 2’ Labeled as herbicides

Weed rollers/rakes

www.TheWeedersDigest.com

Mechanical Control Options

Cutting and shredding boats (“cookie cutters”)

Rotovators – tills sediments Dredgers – sediment removal Harvesters – cut & remove

Pros: Site specific, public perception, use of

harvested biomass

Cons: Requires opens water surface & off-site disposal, $$$ Creates fragments Nonselective, by-catch

Chemical Control Options

Prerequisites for Efficacy Adequate Concentration

Adequate Contact Time

Appropriate Water Quality • Turbidity interferes with diquat

Optimal season and phenological stage

Appropriate chemical for weed species • 2,4-d for dicots

EPA registered herbicides for aquatic use Contact Systemic

Selective Copper Peroxygen granular (GreenClean®

& Phycomycin®)

2,4-D (Aquaclean/

Navigate) Triclopyr (Renovate)

Fluridone (Sonar) Penoxsulam (Galleon)

Bispyribac-sodium (Tradewind)

Broad

spectrum

Endothall, dipotassium salt (Aquathol)

Diquat (Reward) Carfentrazone (Stingray)

Flumioxazin (Clipper)

Glyphosate (Rodeo) Imazapyr (Habitat) Fluridone (Sonar)

Imazamox (Clearcast)

Mention of tradenames does not indicate endorsement – compounds may be available from multiple manufactures and under different tradenames

Aquatic Herbicides Broad spectrum contact herbicides

Endothall (Aquathol K)

• Inhibits respiration & protein synthesis • Typically non-selective (early season applications can control

over-wintering or early emerging weeds) • Liquid and pellet formulations allow spot treatment • Not affected by alkalinity or turbidity

Diquat (Reward, Weedtrine)

• Inhibits photosynthesis & destroys cell membranes • Binds to suspended sediment – not for use in turbid waters

Both can cause quick kill and potential dissolved oxygen problems

Aquatic Herbicides Broad spectrum contact herbicides

Carfentrazone (Stingray)

• Use-patterns still being established • Effective on milfoils & some floating plants (Lemna, Pistia,

Eichhornia, Salvinia) but not others (Landoltia punctata, dotted duckweed)

• Single applications not effective on plants with high nodal regeneration capacity (Ludwigia, Hydrocotyle)

• Irrigation restrictions 1-14 days (depending on treatment area)

Flumioxazin (Clipper)

• Watermeal, duckweed, milfoil, hydrilla Kill by cell membrane disruption (Protox inhibitors – chl biosynthesis)

Quick kill in terrestrial settings, slower with aquatics

Aquatic Herbicides Selective systemic herbicides

2,4-D (AquaKleen, Navigate)

• Granular formulation contains butoxy-ethyl-ester and should not be used in water with T&E salmonids

Triclopyr-TEA (Renovate)

• Also commonly used on purple loosestrife • Liquid and granular

Auxin mimic, plant growth regulator Selective for dicots (e.g., milfoils, ludwigia, water

chestnut)

Aquatic Herbicides “Selective” systemic herbicides

Fluridone (Avast, Sonar)

Selective for Eurasian watermilfoil when contact time and dose can be maintained (long contact time at a low concentration)

Low toxicity, but requires long contact time (45-80 days), carotenoid pigment inhibitor

Non-selective at high application rates Liquid and various pellet formulations

Acts on carotenoid biosynthesis pathway

Aquatic Herbicides Selective systemic herbicides

Penoxsulam (Galleon)

• Inhibits plant-specific enzyme (acetolactate synthase inhibitor – branched chain amino acid inhibition)

• Emergent, floating or submersed weed control • Slow-acting; exposure times for submersed treatments similar to

Fluridone • Irrigation restrictions: Do NOT apply to water to be used for irrigation

of greenhouse or nursery plants or hydroponics • Optimum use patterns still being established

Aquatic Herbicides Broad spectrum systemic herbicides

Glyphosate (Rodeo, AquaMaster)

• Deactivated by sediments • Not effective on submersed weeds • Minimal restrictions on irrigation & potable water • Inhibits amino acid and hormone production by blocking shikimic acid

pathway

Imazapyr (Habitat)

• Inhibits plant-specific enzyme (ALS-inhibitor) • Slow-acting • Moderate residual soil activity

Effective for control of floating and emergent weeds with extensive rhizome/root systems (Phragmites, Typha)

Aquatic Herbicides Broad spectrum systemic herbicides

Fluridone (Sonar)

• Broad spectrum at high application rates

Imazamox (Clearcast)

• Similar use patterns to Imazapyr (ALS-inhibitor) + some extended biomass reduction with submersed plants (hydrilla)

• Slow-acting (impacts in 60-120 days) • Irrigation restrictions vary (still/moving water, depth)

Aquatic Herbicides Selective Contact Herbicides

• Various copper formulations (copper sulfate & chelated

copper compounds)

• Cu is persistent in the environment

• Peroxygen granular (GreenClean® & Phycomycin®)

• Relatively new algaecides • Non-copper based (sodium carbonate peroxyhydrate)

Primarily algaecides Cu is problematic due to effects on salmonid olfaction

Note: These tables are meant only as guidelines. Some herbicides carry specific warnings regarding

toxicity to fish, irrigation water, etc. Please read, understand, and follow all label instructions!

Applications should be made by a certified applicator in accordance with all state and federal regulations.

Source:Whetstone and Heaton. 2013. South Carolina Pest Management Handbook for Field Crops

Note: These tables are meant only as guidelines. Some herbicides carry specific warnings regarding

toxicity to fish, irrigation water, etc. Please read, understand, and follow all label instructions!

Applications should be made by a certified applicator in accordance with all state and federal regulations.

Source:Whetstone and Heaton. 2013. South Carolina Pest Management Handbook for Field Crops

Things to consider • The label! • Perceptions / community • Movement of propagules • Implications of no treatment • Herbicide resistance • NPDES requirements addressed by OR DEQ’s:

• Pesticide General Permit (2300-A): discharge in, over or near surface water

• General Permit for Pesticide Use in Irrigation Systems (2000-J)

Dreissenid Mussels Dreissena polymorpha (zebra mussel)

D. rostriformis bugensis (quagga mussel)

Small, epifaunal, freshwater bivalves

Dreissenid Mussles

Rapid growth (15-20 mm/yr) Prolific reproducers (40K – 1 M eggs/yr) Form dense colonies (200,000+/m2) $0.5 Billion impact if introduced in Columbia Basin

Dreissenid Mussels

Watercraft Inspection Stations

Set up for mussels but find more aquatic weeds than anything else

Crayfish • Signal native to OR and WA

• Invaders can impact benthic community, macrophyte abundance, and aquatic foodwebs

Ringed Rusty Red Swamp Signal Northern

Orcon- Orcon- Procamb- Pacifast- Orconectes

ectes ectes arus acus virilis

neglectus rusticus clarkii leniusculus

Potamopyrgus antipodarum New Zealand Mudsnail

• Small (<5 mm) primarily freshwater snail

• Herbivorous scrapers, grazers

• Can develop very high densities (400k/m2 in Columbia R)

• Density-dependent impacts

– Consume primary production/compete with native gastropods, grazers, and detritivors

• Management

– Prevention

– Gear cleaning

Photo by D.L. Gustafson

Mark Sytsma (503) 725-3833

mark.sytsma@pdx.edu