Use of Herbicides for Control of Submersed Vegetation

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1 Use of Herbicides for Control of Submersed Vegetation Jeremy G. Slade United Phosphorus, Inc. Gainesville, FL

2 Flood Control and Water Delivery

3 Protect Wildlife Habitat

4 Water Use: Hunting? Fishing? Skiing?

5 Invasive Species Disrupt Ecosystems

6 The Scale and Type of Management Can Vary Significantly Aerial Large Lake Irrigation Mgmt. Airboat Small area FL Spring Injection Trmt

7 The Principles Remain the Same Proper Plant Identification Know the Strengths and Weaknesses of the Herbicides Concentration and Exposure Relationships How might Environmental Conditions Impact the Treatment

8 Plant Identification Numerous submersed plants Native and Invasive Some sites require management regardless of species Use of water body Proper Identification = Proper Mgmt.

9 Egeria densa E. najas Hydrilla Monoecious or Dioecious? Elodea?

10 Eurasian Hybrid Northern Variable Milfoil Herbicide Response? Cabomba

11 Management of Submersed Aquatic Vegetation Illinois Pondweed Vallisneria or Eel Grass Strap Leaf Sagittaria Southern Naiad

12 Algae as Invasive Plants? Microcystis bloom in FL AVM linked to bird deaths Management Alternatives Very Limited! Research Golden Algae Prymnesium parvum Massive Fish Kills in TX

13 Sago Pondweed Western Irrigation -Widespread use of Acrolein and Xylene (toxicants) -Acrolein fish kill in OR NPDES permits in West, and now US -Some Mechanical Control Chaining -Irrigation Districts small empires resistant to change -Endothall recently receives registration; pre-emergent evaluations

14 Why Manage Hydrilla or Milfoil? Provides Structure and Food Hydrilla - same role as native plants Clears up the water Do Not Produce Toxins (e.g. golden algae) Valued by the Fishing and Hunting Communities Fishing the Edge Ringneck duck buffet Growth Rate and Ability to Occupy Vast Contiguous Areas are the Problem Access, Flood Control, Fishery Mgmt. Water Quality Just leave us a little

15 Hydrilla has several key competitive advantages Rapid Canopy formation (no native canopy formers) Low light and CO2 compensation points Ability to withstand low oxygen (C4-like photosynthesis) Ability to withstand high temps (canopy > 40 C)

16 Progression of Hydrilla Spread Year Number of States FL (1959) States AL, CA, DE, GA, LA CT, MD, MS, NC, SC, TX, VA AR, PA, TN, WA ID, IN, KY, MA, ME, NJ, NY, OK, WI, WV, KS, OH AZ hydrilla extirpated 1985

17 Hydrilla Moving North Eurasian Watermilfoil - Northern Lakes - Hybridization Curlyleaf Pondweed Northern Lakes

18 Is there a right amount of an invasive plant? If so, then how do you maintain that level?

19 Once Initiated - Herbicide Approach Requires Vigilance - Rare for one treatment to solve a problem - Early detection/rapid Response Programs - Eradication programs multiple years - Invasive Plant Mgmt. multiple years - Rare for one treatment to ruin a lake - Wrong herbicide or use rate possibly - Right herbicide and use rate - No

20 13 Herbicides Registered for Aquatic Use All products have terrestrial uses (fluridone) Glyphosate and 2,4-D- major use on food crops Glyphosate and Imazapyr- Emergent Copper, Endothall, Fluridone- Submersed Diquat, 2,4-D, Clipper, Triclopyr, Carfentrazone, Imazamox, and Penoxsulam, Bispyribac-sodium Both emergent and submersed uses

21 Herbicides for Submersed Plants Product Use Rates Notes Copper 0.25 to 1 Algae, no use restrictions (1900 s) Irrigate Immediately 2,4-D 1.0 to 4.0 Selective Milfoil Control (1950, 76) Diquat 0.15 to 0.37 Short exposure requirement (1958) Turbidity impacts efficacy Endothall 1.0 to 3.0 Key contact for Hydrilla (1960) Fishing restriction removed 06 Fluridone 0.01 to 0.09 Large-scale mgmt; hydrilla, (1986) control can take 1 to 3 months Triclopyr 0.5 to 2.5 Selective Milfoil Control (2002)

22 Herbicides for Submersed Plants Product Use Rates Notes Carfentrazone 0.1 to 0.4 Variable Milfoil, Cabomba (2004) Penoxsulam.01 to.03 Combo w/endothall for Hydrilla (2007) Imazamox.05 to 0.2 Growth Regulation of Hydrilla (2008) Flumioxazin 0.1 to 0.4 Cabomba, Variable Milfoil (2010) Bispyribac-sodium.02 to.045 Combo w/endothall for Hydrilla (2011) Topramezone 2013??

23 Many Factors Impact Submersed Applications Plant Density & Growth Rate Conditions on the DOT Conditions can change Water quality / temp / epiphytes Water exchange (CET) Trmt. Block & edge/ acre

24 Use of Herbicides for Submersed Plants You Treat the Water to Achieve a Desired Aqueous Concentration You are Targeting the Plants! Each Herbicide Has a Plant Species Unique Concentration/ Exposure Profile Concentrations can range from 5 to 5000 ppb Exposure requirements can range from a few hours to months

25 Rate of Dilution/Dispersion Effects Efficacy Following Application Calm Day (Good Lines) Windy Day (Rapid Mixing)

26 Plant Density Can be Very Different But Does Not Change Recommended Use Rate (15 F Temp diff. top/bottom) Plant Density Can effect distribution, thermal gradients Granular vs. Liquid; Trailing Hoses; Time of Day

27 Dilution and Dispersion vs. Exposure Race Between Vertical Mixing And Lateral Dispersion Product Dispersion TARGET Control Area Thermal Gradient US Army Corps of Engineers Engineer Research and Development Center

28 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 e.g. All 3 ppm treatments should work the same Wind/Flow move herbicide off-target Herbicides Are Dumped Into the Water

29 Rates are calculated on a volume basis pumps calibrated to deliver a dose based on boat speed (GPS) 3 ppm in 10 acres with 6 foot avg. depth = 115 gallons Aquathol into 19.6 million gallons of water Can Use GPS to insure that applicator is applying evenly vs dumping

30 Slow Acting Enzyme-Specific Inhibitors Fluridone (1986) PDS inhibitor, Penoxsulam (2007) ALS inhibitor Low mammalian and fish toxicity No restrictions on drinking, swimming, fishing Use rates in the range of 5 to 20 ppb Long-term exposures required Whole-lake or large scale use Large body of research on whole-lake fluridone for control of EWM

31 Auxin-Mimic Herbicides 2,4-D (1959, 1976) and Triclopyr (2002)-disrupt growth & metabolism of sensitive species Epinasty (bending of leaves and stems) Translocated in phloem (moves through the plant) Many monocots are highly tolerant Used for both submersed and emerged plants

32 Contact Herbicides (Diquat and Endothall) - What does that mean in Aquatics? Do not Kill on Contact (e.g. bleach) Must come in Contact with the plant tissue for an appropriate / critical period of time Application techniques are important for these compounds (submersed) Not readily translocated in the plant tissue

33 Environmental Fate Photolysis fluridone (7-30 d), triclopyr (2-7 d) penoxsulam (7-30 d), imazapyr (4-10 d) Microbial 2,4-D (4-10 d), endothall (2-7 d), bispyribac-sodium (30-45 d) Hydrolysis flumioxazin and carfentrazone (hrs to 1 day ph) Deactivation diquat negatively charged particles (sediments minutes to days WQ) Glyphosate binds to cation ions (Ca,Mg) minutes Copper forms complexes that are not biologically active

34 Maximizing Selectivity 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

35 Advantages of Herbicide Use Can treat small as well as large areas Target site is reasonably defined Proper choice & rate = selectivity Newer Products excellent toxicology profiles Compatible with other management options Best tool for initially removing large amounts of invasive vegetation

36 Disadvantages of Herbicide Use Commitment to long-term management Cost ($ to $$$) Can sometimes select for a worse problem Hydrilla Hygrophilia or Limnophila Target plants will ultimately recover Public perception of chemical use Typically based on how it use to be

37 The Situation Matters: Not all infestations are viewed as having equal impact Stakeholders often determine the level of management

38 At some large reservoirs managers accept that an invasive is going to remain dominant Targeted Management Priority Zones Lake Seminole and Lake Eufaula COE Reservoirs

39 Questions to Ask What is the Major Use of the Water? Irrigation, retention, recreation, multi-purpose 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

40 Be Careful Out There!!