Meddlesome milfoils: Parrotfeather & Eurasian watermilfoil

Vanessa MorganCenter for Lakes and Reservoirs

Aquatic Weed WorkshopSalem, Oregon April 24, 2014

Overview

• Haloragaceae (water-milfoil family)• Eight genera;±100 species • Dicot• Annual & perennial herbs• Generally monoecious & aquatic• Myriophyllum spp.

– 30 species worldwide – 14 in North America – 3 non-natives + hybrid(s) in PNW – Some commonly cultivated

Overview

• Identification• Impacts• Habitats & growth habits• Reproduction and dispersal• Control options

– Non-chemical– Chemical

Parrot feather (M. aquaticum)

Eurasian watermilfoil(M. spicatum)

Northern watermilfoil (M. sibiricum)

Whorled watermilfoil (M. verticillatum)

Andean watermilfoil (M. quitense)

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Variable-leaf watermilfoil (M. heterophyllum)

Hybrid watermilfoil (M. spicatum × sibiricum)

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Milfoil Character Comparison

submerged leaves

Status in PNW # leaflet pairs leaf size leaves/whorl emergent leaves (bracts) winter buds (turions)

Northern watermilfoil(Myriophyllum sibiricum)

NATIVE <14 (5-14) < 4 cm long 3 to 5reduced (1-3 mm long);

smaller than flowersyes

whorled watermilfoil(Myriophyllum verticillatum)

NATIVE <14 (5-14) < 5 cm long 4 to 5 2-10 mm long;

deeply pinnately lobedyes

Andean watermilfoil (Myriophyllum quitense)

NATIVE 5-10 1.5 - 4 cm long 2 to 5

0.5-1 cm long; partially toothed

yes

Parrot feather (M. aquaticum)

INVASIVE 10-15 1.5 - 3.5 cm long 3 to 6

2-5 cm long; 16-18 leaflet pairs

stiff, waxy, bright green no

Eurasian watermilfoil (M. spicatum)

INVASIVE > 14 (12-24) 2 - 4 cm long 3 to 6 reduced (1-3 mm long);

smaller than flowersno

Variable-leaf watermilfoil(M. heterophyllum)

INVASIVE 5-12 2-4 cm long 4 to 6 0.5 - 3 cm long;

larger than flowers; serrated/lobed

yes

Hybrid watermilfoil (M. spicatum × sibiricum)

INVASIVE 8-19 1.5-4.2 cm long ? ? ?

ID Verification

• Multiple samples should be taken prior to any treatment

(Moody & Les 2007)

• Morphological samples: CLR, PSU

• Genetic verification: Annis Water Resources Institute, Grand Valley State University, MI

Impacts

• Altered habitats– Outcompetes native plants– Hybridization with native milfoil species– Loss of fish spawning areas– Predator-prey relationships

• Altered food web dynamics– Loss of native food sources for waterfowl– Reduced phytoplankton

• Water quality (temperature, oxygen, pH) • Irrigation – clogging pumps & intakes• Increased mosquito breeding ground• Recreational uses (boating, swimming, fishing) – 1% decrease in

recreation = $500K loss in recreation) (Eiswerth et al. 2000).

EWM Habitats & Growth

• Lakes, reservoirs, ponds, rivers, and streams• Fresh to brackish water (up to 15 ppt)• Depth: (0.5) 1-5 (10) meters• pH range: 5.4 to 11• Fine-textured, inorganic sediment• Early & rapid spring growth (water temp >15 ͦ C )

• Tops out in water < 5 m• Autofragmentation in fall/early winter• Overwintering root crowns

Reproduction & dispersal

• Fragments– Autofragmentation– Allofragmentation

(boats, swimmers, control efforts)

• Seed (EWM & Hybrids) • Water movement &

Waterfowl• Aquaria dumps,

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Non-Chemical Control Options

Method Description Pros Cons Used in

Dredging mechanical sediment removal

long-term control expense, non-selective

shallow small ponds

Drawdown dewatering 4-8 wks

effective on certain species

environ. impacts, non-selective

Small, man-made lakes/ponds

Benthic barriers

material covers plants

effective, long lasting

non-selective, small scale, maintenance

near docks, launches, small areas

Hand cutting/pulling

tools or hand pulling

selective labor intensive, expensive

localized area, rapid response to new infestations

Harvesting mechanical cutting & collection

removes biomass expensive, sediment disturbance, short term, non-selective

heavy infestations with little/no natives

Diver dredging

vacuum removal of whole plants

selective, longer-term, reduced sediment disturb.

expensive, slow localized area, rapid response to new/recent infestations

Rotovation aquatic cultivator, tills sediments

intermediate results

sediment disturbance, spread of fragments

heavy infestations with little/no natives

Biocontrol insects, fish, etc.. selective, long-term

expensive, variable results

heavy infestations

Non-Chemical Control Options

Method Est. costParrotfeather

(M. aquaticum) Eurasian watermilfoil

(M. spicatum)

Dredging variable Drawdown variable ? ?Benthic barriers $0.40-0.50/sq. ft. ? Hand cutting/pulling variable ? Harvesting $2,500-3,000/day

$500-1,000/acre Diver dredging $1,500-2,000/day

(1/4 to 1 acre/day) ? Rotovation $1,500-2,000/day ?Biocontrol Carp - $5-20/fish

Milfoil weevils - $1.20/ind. ?

EWM Chemical Control Options

• Whole lake/pond treatments– Goal: eradication of heavy infestations– Systemics (fluridone, 2,4-D, triclopyr) offer

excellent control • Partial or spot treatments

– Goal: suppress EWM growth, allow native plant recovery

– Contact herbicides (endothall, diquat) offer good control

Prerequisites for Efficacy

• Adequate concentration & contact time– Water exchange & plant biovolume

• Proper placement (proximity for uptake) • Optimal season and phenological stage• Appropriate water quality

– Turbidity interferes with diquat

Application methods

• Liquids• Boat-mounted hose for sub-

surface injections• Foliar sprays

• Pelletized & granular formulations (slow & quick release)• Boat mounted

hopper/spreader to ensure even application* boat speed; rate of delivery from the spreader; swath width

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EWM Control cont…

• Fluridone (Sonar, Avast!)– Systemic, slow acting (45-90 days) – Selective at low doses, non-selective at higher rates

• 8-10 ppb maintained for 10 wks (16-75 ppm recommended label rates)

• FasTEST (SePRO) determines concentration & any needed bump treatments

Reference to specific tradenames is not intended as an endorsement

EWM Control cont…

• 2,4-D– Systemic, fast acting; selective treats dicots– Formulations

• Granular – butoxy-ethyl-ester – Navigate and Aqua-Kleen; toxic to fish/aquatic inverts

–100-200 lbs/acre• Liquid - dimethylamine salt

– DMA*4IVM; – 4 ppm (2.84 gal/acre foot)

EWM Control cont…

• Triclopyr (Renovate 3 – liquid; Renovate OTF – granular)

– Systemic, fast acting – Selective treats dicots; native pondweed species

and coontail, rushes and cattails unaffected– Liquid - 0.75 to 2.5 ppm a.e.; sinking agent > 6’– Granular – 0.5 to 2.5 ppm a.e.

Chemical - recent developments

• Flumioxazin (Clipper)– Non-selective, liquid contact herbicide– 200-400 ppb submersed– Quick kill – potential dissolved oxygen problems

• Bispyribac-sodium (Tradewind) – Non-selective; slow acting, wetable powder– 20-45 ppb, maintained for 60-90 days

• Use patterns still developing

Chemical - recent developments

• Long-term exposure, low rates of 2,4-D or triclopyr may provide control for EWM & hybrids (Glomski et al. 2010, Poovey et al. 2007)

– Individual hybrid population responses

– Impacts to native plants

(Glomski et al. 2010)

(hybrid milfoil)

(EWM)

EWM Chemical Control Options

• Whole lake/pond treatments– Goal: eradication of heavy infestations– Systemics (fluridone, 2,4-D, triclopyr) offer

excellent control • Partial or spot treatments

– Goal: suppress EWM growth, allow native plant recovery

– Contact herbicides (endothall, diquat) offer good control

EWM Chemical cont…

• Contact herbicides– Diquat dibromide (Reward, Weedtrine)

• nonselective, liquid contact herbicide• Not for use in turbid waters• 0.5-2.0 gal/surface acre

– Endothall (dipotassium salt-Aquathol, Cascade) • nonselective, liquid or granular • spot treatments 3.0-5.0 ppm

• Control is temporary – root crowns not killed• Quick kill – potential dissolved oxygen problems

Parrotfeather Habitats & Growth Habits

• Lakes, ponds, canals, and

other slow moving waters• High nutrient inputs• Depth: wet banks to 2 m• pH range: 6.8 to 8• Temperature:16 to 23 ͦ C• Emergent growth ~ 1’ above water; lateral, branching

stolons• Flowers form in spring, no seed production• Submersed leaves senesce in early summer

Wersal and Madsen 2011

Parrotfeather Control

• Robust rhizomes• Waxy cuticle on emergent leaves,

requires wetting agent• Use of contact herbicides (diquat &

endothall) of limited use • No single treatment effective

– Imazapyr & triclopyr most promising for long-term control

Parrot feather – foliar applications

• Imazapyr (Habitat, Arsenal)– Inhibits plant-specific enzyme (ALS-inhibitor)– Slow-acting, moderate residual soil activity– 2-4 pints/acre to actively growing emergent foliage

• Triclopyr (Renovate 3)– 1.0 to 2.5 ppm a.e/acre– Good to fair canopy knockdown, rapid regrowth

• Imazamox (Clearcast)– Slow-acting, impacts 60-120 days– Fair canopy suppression– 1-2 pints/acre

Wersal & Madsen 2007

Parrot feather – subsurface

• Triclopyr (Renovate Max G, Navitrol DPF) – 1.0 to 2.5 ppm a.e./acre– repeat treatments needed

• Endothall (Aquathol K, Aquathol Super K, Cascade)– Whole pond/large area: 2.0-3.0 ppm (1.3-1.9 gal/ac.ft.

liquid; 8.8-13.2 lbs/ac.ft granular) – Spot treatments: 3.0-5.0 ppm (1.9-3.2 gal/ac.ft. liquid; 13.2-

22 lbs/ac.ft granular)

Considerations

• Proper identification & verification• Repeat treatments & continued monitoring• Timing – target plants actively growing and, when

possible, when non-target plants are dormant• Consider IPM approach • Upstream/nearby propagule source• Secondary invasion (replacing EWM with curly pondweed?)

• Chemical treatments: – Partial treatments – 1/3 to 1/2 of total area– Use restrictions (drinking, livestock, irrigation, swimming) – “The label is the law”

Resources

• Biology and Control of Aquatic Plants: A Best Management Practices Handbook (http://www.aquatics.org/aerf_handbook.pdf)

• PNW Weed Management Handbook (http://pnwhandbooks.org/weed/)

• WA Dept. of Ecology, Aquatic Plant Management (http://www.ecy.wa.gov/programs/wq/plants/plantmgmt.html)

• Information Center Online (PICOL) Databases (http://picol.cahe.wsu.edu/LabelTolerance.html)

References

• Eiswerth, M. E., Donaldson, S. G., & Johnson, W. S. (2000). Potential Environmental Impacts and Economic Damages of Eurasian Watermilfoil (Myriophyllum spicatum) in Western Nevada and Northeastern California 1.Weed Technology, 14(3), 511-518.

• Glomski, L. M., & Netherland, M. D. (2010). Response of Eurasian and hybrid watermilfoil to low use rates and extended exposures of 2, 4-D and Triclopyr.Journal of Aquatic Plant Management (JAPM), 48, 12.

• Hofstra, D. E., Champion, P. D., & Dugdale, T. M. (2006). Herbicide trials for the control of parrotsfeather. Journal of Aquatic Plant Management, 44(1), 13-18.

• Moody, M. L., & Les, D. H. (2007). Geographic distribution and genotypic composition of invasive hybrid watermilfoil (Myriophyllum spicatum× M. sibiricum) populations in North America. Biological invasions, 9(5), 559-570.

• Patten, K. (2007). Parrotfeather milfoil (Myriophyllum aquaticum) – Assessment of management alternatives. Final Progress report to WA Dept. of Ecology.

• Poovey, A. G., Slade, J. G., & Netherland, M. D. (2007). Susceptibility of Eurasian watermilfoil (Myriophyllum spicatum) and a milfoil hybrid (M. spicatum x M. sibiricum) to triclopyr and 2, 4-D amine. J. Aquat. Plant Manage, 45, 111-115.

• Vassios, J. D., Nissen, S. J., Koschnick, T. J., & Heilman, M. A. (2014). Triclopyr Absorption and Translocation by Eurasian Watermilfoil (Myriophyllum spicatum) Following Liquid and Granular Applications. Weed Science, 62(1), 22-28.

• Wersal, R. M., & Madsen, J. D. (2007). Comparison of imazapyr and imazamox for control of parrotfeather (Myriophyllum aquaticum (Vell.) Verdc.). J. Aquat. Plant Manage, 45, 132-136