Describing Herbicide Selectivity in Aquatics : The Devil is in the Details BUILDING STRONG® Managing Plants vs. Expectations . There is a general view that a “right way” exists to manage invasive aquatic plants ►The problem: • it is typically done in a state other than your own . Why do aquatic herbicide use patterns vary so significantly? • State to State (rules/laws) • Region to Region (problem) Lakes vs. Reservoirs 2 BUILDING STRONG® Regional Perspectives on Control NE and Upper Midwest . Native plant protection is the priority- natural lakes ► Can have 30+ submersed species in a lake ► Thousands of kettle lakes = native plants . Permitting process is often onerous . State Grants – MN and WI – $2+ million . Scale of herbicide use & rates are often dictated . Limited emergent management (WETLANDS!) ► Purple Loosestrife, Phragmites BUILDING STRONG® Regional Perspective Southern US . Floating Plant – Kill it . Submersed Plant – Kill it . Emergent Plant – Kill it . Something will re-grow . For perspective – in FL multiple large-scale APM efforts going on nearly every work day of year BUILDING STRONG® What is a Herbicide ? . Typically an Organic Compound (ex. ?) . Controlled/Selective Plant Poisoning ►Each herbicide has unique properties . Chemistry of the Herbicide Dictates ►How it behaves in the plant ►How it behaves in the environment 5 BUILDING STRONG® Mechanisms of Tolerance (Selectivity) Herbicide X Not Absorbed Sequestered in the Vacuole Does Not Bind Me To Enzyme Y Metabolized to Z 6 BUILDING STRONG® 13 Herbicides Labeled for Aquatic Use (223 labeled for terrestrial use) Copper (1900’s) 2,4-D (1950’s) Endothall (1960) Diquat (1962) Glyphosate (1977) Fluridone (1986) *Dicamba, Dalapon Simazine, Fenac cancelled in 1987) Triclopyr (2002) Imazapyr (2003) Carfentrazone (2004) Penoxsulam (2007) Imazamox (2008) Flumioxazin (2010) Bispyribac (2011) BUILDING STRONG® Plant Processes & Herbicides . Photosynthesis – Diquat . Amino Acids and Proteins ► Glyphosate,Imazapyr, penoxsulam, imazamox, penoxsulam, bispyribac - Slow acting ► Carfentrazon, flumioxazin – fast acting . Cell Membranes – Endothall and Copper . Pigment Synthesis - Fluridone . Growth Regulation – 2,4-D and Triclopyr Fatty Acid Synthesis, growth inhibition 8 BUILDING STRONG® Aquatic Herbicides - wide variety of sites, plants, scale, and application methods 9 BUILDING STRONG® We treat where people live, work, & play ! 10 BUILDING STRONG® Vast Majority of Permits . Treatments are small in SCALE . Often Not Designed for Selectivity ►Nuisance Plant Removal ►Diquat + endothall + copper (submersed) ►Glyphosate (emergent) . Selectivity derived from - SMALL SCALE 11 BUILDING STRONG® Public Waters – Mgmt./Research Emphasis on Invasive Plants BUILDING STRONG® The Invasive Elite 8 . 1. Hydrilla – submersed (spreading nationwide) . 2. Sago Pondweed (Native to East U.S.) – Irrigation (W) . 3. Eurasian watermilfoil (NE, MW, MS, NW) . 4. Water hyacinth- floating (SE, CA) . 5. Giant Salvinia – floating (LA, TX, MS) . 6. Egeria - submersed (W) . 7. Phragmites – (& other grasses) . 8. Curlyleaf pondweed - submersed (NE, MW) . Bubble Plants – cabomba, variable milfoil, Trapa, ► Water soldier (Canada) BUILDING STRONG ® The 5th Wave of Hydrilla Invasion Coming to a Northern Tier State Near You ? . Glacial Lakes of the upper MW and NE • 1000’s of lakes with potential to support hydrilla . State policies are mixed • Precautionary principle – we don’t want to know how bad hydrilla can get (Eradicate) • We don’t know how bad hydrilla can get (wait & see) . 5 to 10 years from now, what will we say? • We saw the early stages of a major new invasion • Or what was all the fuss about ? 14 BUILDING STRONG® 5 to 10 years from Now . “We saw the early stages of a major new invasion” . “What was all the fuss about - Invasive plants provide Ecosystem Services” 15 BUILDING STRONG® 16 BUILDING STRONG® 50+ years of Diquat Use for Floating Plant Control “Accept Short-term Non-target plant injury vs. Recovery” BUILDING STRONG® Both Sides Treated With Different Herbicides 18 BUILDING STRONG® BUILDING STRONG® Submersed Plant Control Targeting a moving three-dimensional environment “Maintaining adequate exposure is crucial” 20 BUILDING STRONG® TargetingDilution a Moving and DispersionThree Dimensional vs. EnvironmentExposure What Influences Selectivity ? - Scale of Trmt. - Use Rate of Herbicide - Timing of Trmt. TARGET Control Area No Control Desired Thermal Gradient US Army Corps BUILDING STRONG of Engineers Engineer Research and Development Center® Submersed Plant Control . Each Herbicide Has a Plant Species Unique Concentration/Exposure Time (CET) Profile ►Concentrations can range from 5 to 5000 ppb ►CET can range from a few hrs to months BUILDING STRONG® Have we Made the Selectivity Narrative Too Simplistic “Some Herbicides are Selective and Others are Broad-spectrum” Good vs. Bad Herbicides 23 BUILDING STRONG® Glyphosate . Broad-spectrum herbicide that is the most widely used product in the US . No herbicidal activity in the water – WHY ? . Can control underwater portions of most emergent plants ► Ex. Flowering rush, Nymphoides, torpedograss 24 BUILDING STRONG® Glyphosate Translocation ? 25 BUILDING STRONG® Endothall – -Divergent Activity on Members of the Same Plant Family -Similar Morphology does not mean similar herbicide activity Hydrilla Egeria Lagarosiphon BUILDING STRONG® Plant Morphology is Not a Good Predictor of Susceptibility Coontail Eurasian Milfoil Variable Milfoil Limnophila Cabomba Parrotfeather Bladderwort BUILDING STRONG® Herbicide Tolerance or Resistance 1) Hydrilla – Dioecious or Monoecious biotype 1) Eurasian, Northern, or Hybrid Milfoil 2) Fluridone Tolerant ? 2) Fluridone Tolerant (confirmed in MI) 3) Level of Fluridone Tolerance ? 3) 2,4-D Tolerance suspected 4) Mistake in I.D. = big bucks 28 BUILDING STRONG® 2,4-D – “Classic Selectivity” . Selective for Dicots ►Ex. Key Monocots such as • Water hyacinth, bulrush, water stargrass . Won’t control several key dicots ►Crested floating heart, cabomba, . Whole-lake treatments- long exposures • Elodea, naiad, vallisneria, thin pondweed . Inherent sensitivity vs. Exposure pattern 29 BUILDING STRONG® Triclopyr CET Studies: EWM BUILDING STRONG® Fluridone - Broad spectrum and Selective - Rate Based 25 20 Chara, Nitella 15 10 5 EWM, Northern watermilfoil, elodea, Coontail Susceptible Plant Species Plant Susceptible 0 0 25 50 75 100 125 150 Fluridone Concentration 31 BUILDING STRONG® Treatment Timing . The same logic used for early treatment of EWM with fluridone ►Leads to greater sensitivity of Elodea, Coontail and Northern Milfoil . Elodea and Coontail are much more tolerant later in the treatment season ►Slower growth rates ? 32 BUILDING STRONG® Target Plant Biology and Selective Mgmt. Curlyleaf pondweed – ► Rapid early growth (under ice), senescence in late June/July ► Turions - quiescent and viable for 3+ years . Highly susceptible to endothall ► Most Potamogetons are “highly susceptible to Endothall” ► Treat when CLP is active and Native Plants are “Dormant” . Temporal Selectivity is possible BUILDING STRONG® Example - Carman’s Bay on Lake Minnetonka - Treated in 2010 and 2011 -96 ac. treated in 2010 – Triclopyr 1.0 mg/L - 83 ac. treated in 2011 – Triclopyr 1.25 mg/L 2010 results – Milfoil frequency in Sep = 67% 2011 results – Milfoil frequency in Sep = 2% WHY THE DIFFERENCE ? 1. 2. 3. 34 BUILDING STRONG® Carmans (outside plot) 300 Site 7 Site 8 Site 9 250 200 150 Triclopyr, ppb Triclopyr, 100 50 0 8 9 10 11 12 13 14 15 Sample Date (June 2011) BUILDING STRONG® Percent frequency results: St. Albans Bay, MN 6/11 6/09 8/09 8/11 St. Albans Bay, MN Exotic SAV (%) Eurasian watermilfoil 72 64 70 0 Curly-leaf pondweed 16 6 1 0 Treatment Assessment Native SAV (%) Bidens beckii 14 6 8 3.5 1. Exotics at 0% freq. Ceratophyllum demersum 41 42 34 50 Elodea Canadensis 14 19 8 18 2. Reduction of 3 Najas flexilis 3 4 4 12 native SAV Potamogeton amplifolius 16 16 6 21 Potamogeton praelongus 1 0.6 7 5 Potamogeton richardsonii 25 18 11 24 Potamogeton robbinsii 43 44 36 39 No change Potamogeton zosteriformis 14 22 10 1.7 - SAV per point Ranunculus longirostris 0 6.7 4 0.4 Stukenia pectinata 0 0.6 0 10 - number of SAV Vallisneria Americana 13 0 26 35 species Zosterella dubia 0 12 23 1.7 Utricularia spp. 0 0.6 1 2 Myriophyllum sibiricum 2 0 1 1 - Biovolume and Cover Chara spp. 11 6 3 11 Littoral samples (depth < 15 ft) 190 190 Samples with SAV 156 173 Native SAV species per point 2.3 2.6 BUILDING STRONG Number of native SAV Species 15 15 ® St. Albans top 7 6/11 St. Albans Bay Top 5 8/11 10 10 mean dry weight mean dry weight 8 17 8 11 9 6 6 11 dry weight dry 4 4 4 dry weight (g) weight dry 4 3 8 3 5 2 1 2 2 0 0 MYSP PORO CEDE POZO ZODU POAM PORI CEDE PORO POAM PORI Chara species Species St. Albans low 6 St. Albans Bay Low 5 1.4 mean dry weight 1.4 1.2 mean dry weight 1.2 1.0 1.0 0.8 0.8 6 1 0.6 7 dry weight dry 0.6 dry weight (g) weight dry 0.4 0.4 4 1 0.2 1 1 2 0.2 3 1 1 0.0 0.0 RALO ELCA BIBE POPR CHARA POCR POZO Nitella ELCA ZODU Naiad species Species BUILDING STRONG® Hydroacoustic Assessment on Transects in 4 treated Bays on Minnetonka No reduction in Plant Volume between June and August Transect June Biovolume2 August Biovolume 20 – 170 29 44 8 – 17 27 46 52 – 198 15 32 233 – 259 27 35 150 – 262 27 28 168 -237 24 45 167 – 236 21 51 22 - 123 22 33 38 BUILDING STRONG® Ongoing Research – Focus on EWM and Natives- Timing, Long-term exposures, Robust plants, etc 1.2 m Seed Research BUILDING STRONG® Differing Views on Selectivity . 1) Distribution/abundance of key native species is most important ► Loss of species vs. injury/recovery . 2) Native plants are not impacted during the course of Milfoil control . 3) Reduction of some natives-balanced by long-term milfoil control & native recovery . 4) Others ? BUILDING STRONG® Parting Shot Plants Can Sustain Significant Injury but recover quite rapidly Efficacy and Selectivity Assessments Can Be Influenced by When we Make Assessments BUILDING STRONG® Why is APM Complex ? .