Idea Transcript
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