Chemical Control of Aquatic Weeds - MidSouth Aquatic Plant

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Chemical Control of Aquatic Weeds Ryan M. Wersal, PhD Lonza Microbial Control, Alpharetta Innovation and Technology Center

Benefits of Aquatic Plants • Stabilize lake sediments, reduce resuspension • Increase sedimentation, reduce turbidity • Provide habitat for insects, forage fish, fish spawning and YOY fish

• Provide food for waterfowl, other animals

Native Vs. Non-native

Plant Species Designation • Aquatic plant species can be designated as: – – – – – –

Native Non-native Invasive Native Invasive Non-native Invasive And Others (i.e. Non-native Naturalized)

• This often creates confusion with the public and resource managers • As well as determining management strategies – Including herbicide selection

Goal of Management • Remove nonindigenous plants and restore a diverse community of desirable native plant species

Pretreatment

4 WAT

12 WAT Pond near Starkville, MS 70% coverage by waterhyacinth

What Do Herbicides Do? • Controlled/selective plant poisoning – applied to soil (root uptake), water, and/or leaves (foliar uptake) – contact or systemic – selective vs. non-selective

How Herbicides Work • Mode/mechanism of action, where a specific plant process is targeted – – – – –

photosynthesis pigments enzymes growth hormonal balance

DQ

DQH2

O2 -

Advantages of Herbicide Use • Cost effective • Predictable, consistent efficacy

• Relative ease of application • Minimal ecosystems impacts

Advantages of Herbicide Use • Can treat small as well as large areas • Proper choice, rate, timing = selectivity • Newer Products – excellent toxicology profiles • Compatible with other management options

• Best tool for initially removing large amounts of nuisiance vegetation

Disadvantages of Herbicide Use • Commitment to long-term management • Use restrictions

– When/where you can apply – Drinking, swimming, fishing, irrigation, livestock

• Can sometimes select for a worse problem

• Target plants can recover • Public perception of chemical use – Human/eco-toxicology issues – Fear of pesticides

Misconceptions with Aquatic Herbicides • Aquatic plants “take up” most of the herbicide – Plant uptake = 1 to 5% of herbicide

• Herbicides mix rapidly top to bottom – Herbicide trapped via thermal gradients

• Dispersion is a minor factor – All 3 ppm treatments should work the same – Wind/Flow move herbicide off-target

• Herbicides Are Dumped Into the Water

Potential Environmental Concerns • Potable Water • Lowered dissolved oxygen (DO) and warm water – Whole vs. Partial treatment – Fish mortality may result

• Nutrients released

– Increased turbidity (algal bloom)

• Crop/landscape damage due to irrigation (MS Delta alligatorweed and soybeans) – Choice of herbicide • 1/2 life, sensitivity of non-target plants – Posting requirements – Time, Setback Distance, Herbicide Concentration

13 Herbicides Registered for Aquatic Use • Section 3 herbicides • All products have terrestrial uses

– Glyphosate and 2,4-D - major use on food crops

• Glyphosate and Imazapyr - Emergent • Copper, Endothall, Fluridone - Submersed • Diquat, 2,4-D, Triclopyr, Carfentrazone, Imazamox, Penoxsulam, Flumioxazin, and Bispyribac-sodium – Emergent and submersed uses

Aquatic Herbicide Mode of Action 2,4-D

Auxin mimic / plant growth regulation

Bispyribac-sodium

Plant enzyme inhibition / ALS

Carfentrazone-ethyl

Inhibits PPO enzyme / chlorophyll

Copper

Inhibits photosynthesis

Diquat

Inhibits photosynthesis

Endothall

Respiration / photosynthesis inhibition

Flumioxazin

Inhibits PPO enzyme / chlorophyll

Fluridone

Pigment synthesis

Glyphosate

Plant enzyme inhibition / EPSPS

Imazamox

Plant enzyme inhibition / ALS

Imazapyr

Plant enzyme inhibition / ALS

Penoxsulam

Plant enzyme inhibition / ALS

Triclopyr

Auxin mimic / plant growth regulation

Herbicide Translocation and Selectivity Herbicide

Translocation

Selectivity

2,4-D

Systemic

Selective

Bispyribac-sodium

Systemic

Broad spectrum

Carfentrazone-ethyl

Contact

Selective

Copper

Contact

Broad spectrum

Diquat

Contact

Broad spectrum

Endothall

Contact

Selective (Timing)

Flumioxazin

Contact

Broad spectrum

Fluridone

Systemic

Selective (Rate)

Glyphosate

Systemic

Broad spectrum

Imazamox

Systemic

Selective

Imazapyr

Systemic

Broad spectrum

Penoxsulam

Systemic

Selective (Rate)

Triclopyr

Systemic

Selective

Herbicide Degradation & Half-life Herbicide

Degradation

½-life in water (days)

2,4-D

Microbial, Photolysis

7 to 48

Bispyribac-sodium

Microbial

Carfentrazone-ethyl

Hydrolysis, Photolysis

3 to 8 (pH dependent)

Copper

Chemically bound

Hardness dependent

Diquat

Adsorption, Photolysis

1 to 7

Endothall

Microbial

4 to 7

Flumioxazin

Photolysis, Microbial

3-5 d (pH 5) to 14-22 min (pH 9)

Fluridone

Photolysis, Microbial

20+

Glyphosate

Adsorption, Microbial

14

Imazamox

Microbial, Photolysis

7 to 14

Imazapyr

Photolysis, Microbial

2 to 4

Penoxsulam

Photolysis, Microbial

15+

Triclopyr

Photolysis, Microbial

0.5 to 3

~ 30

Aquatic Herbicide Toxicity Typical Rates in H2O (ppm)

Bluegill 96-hr LC-50 (ppm)

0.5 to 4.0

168

Bispyribac-sodium

0.015 to 0.045

> 100

Carfentrazone-ethyl

0.2

>5000

Copper

0.2 to 1.0

Soft water: 0.88, Hard water: 7.3

Diquat

0.1 to 0.37

245

Endothall

0.3 to 3.0

Dipotassium salt: 343, Alkylamine salt: 0.94

Flumioxazin

0.1 to 0.4

>21

0.005 to 0.03

891

Glyphosate

NA

>1000

Imazamox

0.05 to 0.075

>100

Imazapyr

NA

>100

Penoxsulam

0.01 to 0.04

103

Triclopyr

0.75 to 2.5

891

Herbicide 2,4-D

Fluridone

Copper (1950’s) • Target weeds: hydrilla, planktonic algae, filamentous algae, chara/nitella, coontail, milfoil spp., pondweed spp. • Subsurface application

• Typical use rates: 0.5 to 1 ppm • Max concentration: 1 ppm

• Restrictions

– Label changes are coming for copper products

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

2,4-D (1959)

• Target weeds: Eurasian watermilfoil, water hyacinth, coontail, waterlily, parrotfeather

• Subsurface and foliar application • Typical use rates: 0.5 to 4 ppm, 2 to 4 lb ae/A

• Max concentration and rate: 4 ppm, 4 lb ae/A • Restrictions – – – – – –

Potable water intake: 5 to 14 days (1 to 4 ppm) Drinking water setback: 600 to 2400 ft (1 to 4 ppm) Swimming (butoxyethanol ester only): 24 hr Drinking: concentration <70 ppb Labeled crop irrigation: none Unlabeled crop irrigation: concentration <100 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Endothall (1960)

• Target weeds: hydrilla, coontail, pondweed spp., milfoil spp. • Subsurface application • Typical use rates: 0.3 to 3 ppm • Max concentration: 5 ppm • Partial lake use

• Restrictions

– Livestock consumption

• 7 day for up to 0.5 ppm • 14 day for up to 4.25 ppm • 25 day for up to 5 ppm

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Diquat (1962) • Target weeds: hydrilla, coontail, salvinia spp., duckweed spp., water hyacinth, waterlettuce • Subsurface and foliar application • Typical use rates: 0.1 to 0.37 ppm • Max concentration: 0.37 ppm • Partial lake use • Restrictions – – – – –

Drinking: 1 to 3 days Livestock: 1 day Turf and ornamental landscape irrigation: 1 to 3 days Food crop and production, ornamental irrigation: 5 days Fishing and swimming: none

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Glyphosate (1977) • Target weeds: salvinia spp., alligatorweed, cattail, water hyacinth, waterlettuce, torpdeograss, cogongrass, phragmites • Foliar application

• Typical use rates: 3 to 6 pints/A • Max rate: 7.5 pints/A or 2% solution • Restrictions

– Potable water intake: <700 ppb within ½ mile – Others: none

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Fluridone (1986) • Target weeds: hydrilla, salvinia spp., pondweed spp., Eurasian watermilfoil • Subsurface application • Typical use rates: 0.005 to 0.03 ppm • Max concentration: 0.15 ppm • Long-term exposures required (60+ days) • Whole-lake or large scale use • Restrictions – Potable water intake: <20 ppb within ¼ mile – Irrigation: 7 to 30 days

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Triclopyr (2002) • Target weeds: milfoil spp., water hyacinth, waterlily, alligatorweed • Subsurface and foliar application • Typical use rates: 0.75 to 2.5 ppm, 1 to 3 lb ae/A • Max concentration and rate: 2.5 ppm, 6 lb ae/yr • Restrictions

– Potable water/drinking: see label for specifics – Labeled crop irrigation: none – Irrigation: 120 days or <1 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Imazapyr (2003) • Target weeds: duckweed, alligatorweed, cattail, parrot feather, water hyacinth, waterlettuce, torpdeograss, cogongrass, malaleuca, phragmites • Foliar application

• Typical use rates: 2 to 6 pints/A • Max rate: 6 pints/A (1.5 lb ai/A) or 5% solution • Restrictions

– Potable water intake: do not use within ½ mile – Irrigation: 120 days or <1 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Carfentrazone-ethyl (2004) • Target weeds: water lettuce, duckweed, watermeal, giant salvinia • Subsurface and foliar application: pH dependent • Max concentration and rate: 0.2 ppm, 0.2 lb ai/A • Restrictions

– Potable water intake: within ¼ mile or <200 ppb – Irrigation: 14 days if >20% treated or 1 day if <20%; concentrations <1 ppb – Drinking: 1 day if >20% treated – Livestock: 1 day if >20% and concentrations <200 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Penoxsulam (2007) • Target weeds: hydrilla, salvinia spp., water hyacinth, duckweed spp., Eurasian watermilfoil, egeria • Subsurface and foliar application • Typical use rates: 0.01 to 0.04 ppm • Max concentration: 0.15 ppm • Long-term exposures required (60+ days) • Whole-lake or large scale use • Restrictions

– Potable water intake: <20 ppb within ¼ mile – Irrigation restrictions dependent upon crop

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Imazamox (2008) • Target weeds: hydrilla, alligatorweed, common salvinia, water hyacinth, water lettuce, curlyleaf pondweed • Subsurface and foliar application • Typical use rates: 0.025 to 0.075 ppm

• Max concentration: 0.5 ppm • Whole-lake or large scale use

• Restrictions

– Potable water intake: <50 ppb within ¼ mile – Do not irrigate greenhouses, nurseries, or hydroponics – Irrigation: concentration ≤50 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Flumioxazin (2010) • Target weeds: hydrilla, Eurasian watermilfoil, sago pondweed, salvinia spp., water lettuce, alligatorweed • Subsurface and foliar application: pH dependent • Typical use rates: 0.100 to 0.400 ppm or (6-12 oz./A buffer spray solution to < 7 pH) • Max concentration: 0.400 ppm • Whole-lake or large scale use • Restrictions

– Do not apply to waters used for crayfish farming – 5 day Irrigation restriction

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Bispyribac-sodium (2011) • Target weeds: hydrilla, Eurasian watermilfoil, salvinia spp., water hyacinth, water lettuce, alligatorweed • Subsurface and foliar application • Typical use rates: 0.020 to 0.045 ppm (1-2 oz./A)

• Max concentration: 0.045 ppm • Whole-lake or large scale use

• Restrictions

– Treated water can not be used for livestock until ≤ 1 ppb – Do not apply to waters used for crayfish farming – Irrigation restriction for food and ornamental ≤1 ppb

Due to multiple manufacturers, follow all label instructions regarding rate, adjuvants, application technique, and use restrictions. Check with appropriate regulatory agencies before purchasing or applying pesticides to the water. Always Follow The Label!

Defining Use Patterns for Herbicide Applications • Concentration exposure time relationships (CET) • Herbicide applications for submersed plant control are impacted by: – The concentration of the herbicide in water that surrounds the target plant – The length of time a target plant is exposed to dissipating concentrations of that herbicide

Concentration and exposure time relationships

Endothall v EWM (Netherland et al. 1991)

Triclopyr v EWM (K. Getsinger, USAERDC)

Other Factors Influencing Aquatic Weed Control • pH (carfentrazone, flumioxazin) – Acid < 7=neutral > basic

• Hardness/alkalinity (copper) – Soft < 50 ppm CaCo3 >Hard

• Turbidity (diquat) – Organic – Inorganic

Other Factors Influencing Aquatic Weed Control • Thermal Stratification – Drop hoses – Handgun – Pellet formulations

• Water flow

– Herbicide placement – Slow release formulations – Metered/sequential applications

• Growth stage/time of year/plant maturity • Adequate herbicide coverage/distribution

Site Specific Water Exchange Characteristics • Utilizing CET relationships & application timing to maximize herbicide efficacy

30000 25000 20000 15000 Water Discharged

10000 5000

A 3: M 00 A 5: M 00 A 7: M 00 A 9: M 00 A 11 M :0 0 A 1: M 00 PM 3: 00 P 5: M 00 PM 7: 00 P 9: M 00 P 11 M :0 0 PM

0

1: 00

Water Discharge in cfs

• Flowing water on regulated reservoirs presents unique challenges

Water Discharge for 7/23/2009

Noxon Rapids Reservoir, MT

Understanding How Water Exchange Affects Applications

Plant Height from Lake Bottom to Water Surface (cm)

Plant Growth Stage: Curlyleaf Pondweed 200

Curlyleaf Pondweed

Flowering and Turion Formation

Ice Cover 150

Target Management

Plant Senescence (Only Turions Remain)

Target Management

Turion Sprouting

100

50

0 Jan

Mar

May

Native Plant Growth

Jul

Sep

Nov

Jan

Maximizing Selectivity • The susceptibility or tolerance of different plants to a herbicide – Concentration/rate, absorption, translocation, metabolism, conjugation, accumulation & secretion

• Timing can have a major impact on selectivity – Different species have maximum growth at different times – E.g. Curlyleaf pondweed

• Species composition is very important in herbicide selection – Lack of impacts to non-targets may be equally or more important than impacts on the target

Weed Shifts Related to Herbicides • In general, management (cropping) systems impose very high selection pressures on weed communities, resulting in weed population shifts (Owen (2008) • These shifts are towards populations with adaptive traits that overcome management tactics and subsequently increase in density • High level of seed production = High genetic variability • Biotypes that are more competitive

• Ex. Using auxin herbicides to manage Eurasian watermilfoil, curlyleaf pondweed fills the niche vacated by Eurasian watermilfoil

Weed Shifts Related to Herbicides • Even when using broad spectrum herbicides, not all species will respond similarly at the rates and exposure time used

Hardin 1985 “every good pesticide selects for its own failure”

Case New Holland

Herbicide Resistance •

Shift in the amount (rate) required to achieve a similar level of control



Complete lack of control

Herbicide Resistance • A shift in the population of a once susceptible biotype to a biotype that is resistant to normal application rates • SO HOW DOES IT HAPPEN?!

Selectivity Selectivity Selectivity

One plant survives and then……

Source:J. L. Gonsolus. Herb. Res. Weeds. 1998

Types of Resistance • Cross resistance: weed is resistant to >1 herbicide with the same mode of action • Multiple resistance: weed is resistant to >1 herbicide with different mode action

Mechanisms of Resistance/Tolerance

X

Herbicide X not absorbed

X Sequestered in vacuole X does not bind to enzyme Y

Y1 X metabolized to Z

Target site Resistance

Source: J. L. Gonsolus. Herb. Res. Weeds. 1998

What Enhances Chances? • Single site of action • Multiple applications per season, persistence of herbicide in environment

• Repeated use of same material • Stand alone treatments

• Low, sublethal rates • Some plants are just more likely

– highly outcrossed species – high genetic plasticity, vegetativeness

Super Weeds? • The herbicide did not cause the mutation, it was preexisting in the population • The repeated use has selected for an alternative biotype

Herbicide Resistance (Aquatics) • Landoltia resitant to diquat • Hydrilla verticillata resistant to fluridone and suspected resistance to endothall • Myriophyllum spicatum – suspected fluridone resistance • Hybrid milfoil??? • Others???

Consequences of Resistance • •

May show cross resistance to other herbicides Increasing herbicide rates – – –



increase costs/acre decrease in selectivity postponing the inevitable

Change control tactics, herbicides – –

increase costs/acre, fuel costs decrease in selectivity

Resistance Management • Rotate herbicides with different modes of action • Tank mix multiple modes of action – – – –

Less convenient? Increase cost? Increase crop injury risk? Reduce the window of application??

• IPM approach – Biological – Mechanical – Physical

Questions to Ask Prior to Applying • What is the Major Use of the Water ? – Irrigation, retention, recreation, multipurpose

• Where Does the Treated Water Go ? – What is downstream and how fast does it get there

• Are Fish an Important Resource ? – Pay attention to water temperature, DO, plant mass

• Is the site susceptible to rapid turnover ? – Flow, significant rain event

• What non-target plant species are present? – Herbicide selection, determine time of year to treat

Other Resources UNIVERSITY

PROFESSIONAL SOCIETY

Aquatic Plant Management Society Center for Aquatic and Invasive Plants www.apms.org aquat1.ifas.ufl.edu North American Lake Management Society Mississippi State University GRI www.nalms.org www.gri.msstate.edu MSU Extension Service msucares.com/pubs/publications/p1532aquati GOVERNMENT Aquatic Plant Control Research Program c.pdf www.wes.army.mil/el/aqua/aqua.html North Carolina State University http://www.weedscience.ncsu.edu/aquaticweeds/ USGS Aquatic Nonindigenous Species Site nas.er.usgs.gov default.asp National Biological Information Infrastructure invasivespecies.nbii.gov FOUNDATION Aquatic Ecosystem Restoration Foundation www.aquatics.org

Acknowledgements • Dr. Chris Mudge • Dr. Greg MacDonald • Justin Nawrocki

Contact Information Ryan Wersal, PhD Aquatic Plant Scientist Lonza Microbial Control Alpharetta Innovation and Technology Center 1200 Bluegrass Lakes Pkwy Alpharetta, GA 30004 Ph (678) 624-5891 Cell (770) 364-4818 Fax (678) 624-5676 [email protected]

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Chemical Control of Aquatic Weeds - MidSouth Aquatic Plant

Chemical Control of Aquatic Weeds Ryan M. Wersal, PhD Lonza Microbial Control, Alpharetta Innovation and Technology Center Benefits of Aquatic Plant...

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