1

Aquatic Herbicides

AQUATICS WORKSHOP – INVASIVE SPECIES ID and MANAGEMENT

Jim Petta, Valent

2

Objectives

Why aquatic herbicides?

What are they?

Herbicide classes and Key examples

Selecting the right tool

3

Flood Control and Water Delivery

4

Protection of Wildlife Habitat

5

Water Use: Hunting? Fishing? Skiing?

6

Invasive Species Which Destroy Ecosystem

7

Human Life Impacts Waterways

There are essentially almost no “natural areas” in the

world (without humans)

Humans have impacted waterways wherever they live

including Florida long before Europeans arrived (Mexico

City, others)

“Natural” means to manage “unnatural” impacts are limited

at best

8

Why Aquatic Herbicides?

Because they work

− Cost effective

− Efficient

− Protect water resource

− Minimal risk to the user and the environment

9

Pretreatment (cabomba, Highlands County)

10

7 DAT

11

30 DAT

Clipper applied at 200 ppb

12

Duckweed, pretreatment

13

14 DAT

Clipper at 200 ppb

14

What are Aquatic Herbicides?

Organic chemicals which are highly effective at low doses

in controlling or managing target plant species

Very limited in number due to high barrier to entry

(environmental, toxicology, efficacy)

Selective tools for aquatic plant managers to protect,

maintain, or enhance water resources

− Are herbicides selective or non-selective? Why or why not?

15

Common Myths about Aquatic Herbicides

True or False?

− Aquatic herbicides are toxic to fish……

− Aquatic herbicides are toxic to people…..

− Aquatic herbicides make our water unsafe to drink….

− Aquatic herbicides are all the same…..

16

How Do We Know if they are Safe to Use?

All herbicides must be registered by the USEPA and

deemed to offer more benefit than the risk involved in

their use (risk/benefit; not precautionary principle).

No action is without risk; so according to EPA, nothing is

“safe”. Tools have degrees of risk; it is the aquatic plant

manager who manages this risk/benefit

No product is allowed for use in Florida waters until

registered by the State following USEPA registration;

again reviewing the data package.

17

Toxicology= The dose makes the poison

Herbicides are labeled at doses that are effective without

unacceptable toxicities to non-target plants or animals

Rate ranges allow managers flexibility to manage target

situations depending on lake/pond conditions

Labels are written to the dosage/exposures

− Go off the label, all the toxicity data are no longer relevant

− The label is written to protect you and the environment and

to direct the optimal method of use for the product

18

Risk/Benefit or Precautionary Principle?

Risk/Benefit

Risk:

− Car wreck

− Traffic jam

− CEU’s

− Meeting was important

− Donuts and coffee

Precautionary

Car wreck

Traffic jam

Meteor strike

Atomic war

Car jacking

Others? Which must be

listed….

No benefit measurement

So why would you drive

anywhere?

19

What Makes Herbicides Work?

Active plant growth

− Good growing conditions

− Non-stressed from injury, weather, etc.

Young, new growth usually most susceptible

Direct activity depends on mode of action by class

20

Herbicide Classes

HRAC

Group Mode of Action Chemical Family Active Ingredient Key Brand(s)

B

Inhibition of acetolactate synthase ALS (aceto

hydroxy acid synthase AHAS) sulfonylureas bensulfuron-methyl

imidazolinones imazamox ClearCast

imazapyr Habitat

triazolopyrimidines penoxsulam Galleon

pyrimidinyl (thio) benzoates bispyribac-Na Tradewind

D Photosystem I electron diversion bypyridiliums diquat Reward

E Inhibition of protoporphyrinogen oxidase (PPO) N-phenylphthalimides flumioxazin Clipper

triazolinones carfentrazone-ethyl Stingray

F1

Bleaching: Inhibition of carotenoid biosynthesis

at the phytoene desaturase step (PDS) not classified fluridone Sonar

G Inhibition of EPSP synthase glycines glyphosate Rodeo

O Action like indole acetic acid (synthetic auxins) phenoxy-carboxylic acids 2,4-D multi.

pyridine carboxylic acids triclopyr Renovate

Z unknowns dicaroboxylic acids endothal Aquathol

21

ClearCast Specifications

Active Ingredient: imazamox

Herbicide Family (Chemical Class): imidazolinones

Mode of Action: acetolactate synthase (ALS) inhibitor

Key Points:

− Slow, systemic

− Regulatory at use rates; plant death?

− Exempt from tolerances

− Wild taro, Chinese tallow

22

Habitat Specifications

Active Ingredient: imazapyr

Herbicide Family (Chemical Class): imidazolinones

Mode of Action: acetolactate synthase (ALS) inhibitor

Key Points:

− Slow systemic (requires long contact time)

− Excellent on marginal and floating plants

− Little to no submersed activity

− Tough grasses: torpedo and Trop. American WG

23

Galleon Specifications

Active Ingredient: penoxsulam

Herbicide Family (Chemical Class): triazolopyrimidines

Mode of Action: acetolactate synthase (ALS) inhibitor

Key Points:

− Slow systemic (requires long contact time)

− Excellent on Hydrilla, others

− Controls fluridone resistant Hydrilla

− Selectivity to non-targets must be managed

24

Tradewind Specifications (New in 2011)

Active Ingredient: bispyribac

Herbicide Family (Chemical Class): pyrimidinyloxybenzoic acid

Mode of Action: acetolactate synthase (ALS) inhibitor

Key Points:

− Slow systemic (requires long contact time)

− Excellent on Hydrilla

− Highly selective for Southern naiad

− Controls fluridone resistant Hydrilla

− Selectivity to non-targets must be managed

25

Sonar Specifications

Active Ingredient: fluridone

Herbicide Family (Chemical Class): not classified

Mode of Action: Bleaching by the inhibition of carotenoid biosynthesis at the phytoene desaturase step (PDS)

Key Points:

− Slow systemic (requires long contact time)

− Excellent on sHydrilla, EWM, watermeal, others

− Highly selective via dose

− Documented Hydrilla resistance/tolerance in Florida

− Non-flowing water

26

Rodeo Specifications

Active Ingredient: glyphosate

Herbicide Family (Chemical Class): glycines

Mode of Action: Inhibition of EPSP synthase

Key Points:

− Medium speed systemic

− Excellent on cattail, floating and marginal plants

− No submersed activity

27

Clipper Specifications (New in 2011)

Active Ingredient: flumioxazin

Herbicide family: N-phenylphthalimides

Mode of Action: Initiates cell membrane disruption by

protoporphyrinogen oxidase (PPO) inhibition

Key points:

− Fast acting contact

− Controls both floating and submersed plants

− Short half life related to pH (alkaline hydrolysis)

28

Clipper Environmental Fate

Flumioxazin – Aquatic Plant Management

Hydrolysis

pH 5: 3.4 - 5.1 days

pH 7: 21.4 - 24.6 hours

pH 9: 14.6 - 22.0 minutes

Clipper quickly dissipates from the water column; does not accumulate in

soil sediment

Short half life

29

Reward Specifications

Active Ingredient: diquat

Herbicide family: Bipyridiliums

Mode of Action: Photosystem I electron diversion (cell

membrane disruption)

Key points:

− Fast acting contact

− Controls both floating and submersed plants

− High binding to clay lattice

30

Aquathol Specifications

Active Ingredient: endothall

Herbicide family: Dicarboxylic acid

Mode of Action: Unknown/defined

Key points:

− Moderately fast acting contact

− Controls many submersed plants

− Potential microbial degradation

31

2,4-D Specifications

Active Ingredient: 2,4-D

Herbicide family: phenoxy carboxylic acids

Mode of Action: Action like indole acetic acid (synthetic

auxins)

Key points:

− Highly selective to control broadleaf plants

− Systemic, slow-acting

− Controls submersed, floating, and marginal plants

32

Renovate Specifications

Active Ingredient: triclopyr

Herbicide family: pyridine carboxylic acids

Mode of Action: Action like indole acetic acid (synthetic

auxins)

Key points:

− Systemic

− Selective control of submersed and emergent plants

33

Which Aquatic Herbicide Should I use?

Selecting the right tool starts with the objectives of the

water body

− Drinking, irrigation, fishing, skiing, aesthetics, flood control,

all?

− What plants are present and which should be removed and

why?

− Speed and timing…..hurricane approaching or do we have

90 days?

− Cost? But is cost the main driver in aquatics?

34

Killing Plants is Easy……but!

Protecting and managing a water resource is not!

− Selecting the right tool is critical. PLANT ID IS THE

NUMBER ONE ISSUE IN PRODUCT PERFORMANCE.

− All herbicides are NOT the same, even within classes

− Checkpoints of actions…..

35

Resistance? Is it Real?

Yes!

Multiple examples

Interesting to note, that generally, as toxicity decreases, resistance potential increases….?!? Why?

− Single site, multi-site, or unknown

− Newer products, single site, higher resistance risk!

We must manage all products with a long term view!

− Program

− Rotation

− Tank mixes………combinations and sequentials!

36

Where is the fit for the Right Herbicide?

EfficacyControl the target?

Water flow?

Toxicology

No drinking, fishing

or swimming

restrictions

Non-target plants?

Water use?

Environmental

Fate

Herbicide Tool

37

Aquatic Herbicides are…..

Critical Tools for aquatic plant management

Environmentally compatible to lake management

programs

Not all alike; make sure the tool fits the need of the site

Herbicides are only better than other herbicides due

to the site and circumstances!

38

The Two Newest Tools in the Box

39

And Tradewind