UMISC Conference Duluth, MN October 20-22, 2014
Michelle Nault, Wisconsin DNR Science Services John Skogerboe, U.S. Army Corps of Engineers (retired) Herbicide Monitoring
What: Collect data on herbicide concentration and exposure times under varying operational conditions Purpose: To provide recommendations for improving control of invasive aquatic plants and minimizing damage to native plants Outputs: Scientific evaluation of herbicide treatments Nault et al. 2014. Whole-lake 2,4-D for EWM Control. Lake & Res 30:1-10 Nault et al. 2012. NALMS LakeLine 32(1):19-24 Large Scale Treatment Factsheet (PUB-SS-1077 2011) CET Experiments Indoor Growth Chambers Outdoor Mesocosm Tanks
• Wide range of herbicide concentrations and exposure times (CET) • Replicated studies • Species sensitivity 2,4-D Concentration/Exposure Time Small-Scale ‘High’ dose Green & Westerdahl, 1990 Short exposure JAPM 28:27-32 2.0
1.5
ae ppm 1.0 Large-Scale ‘Low’ dose 0.5 Long exposure
Recommended 2,4-D label rate: 2.0 – 4.0 ppm (Hours) 1.0 ppm = 1.0 mg/L = 1000 ppb Herbicide Exposure Time • Dissipation: horizontal and vertical movement of herbicide within the water column – Treatment area relative to lake – Wind – Water flow – Water depth • Degradation: physical breakdown of herbicide into inert components – Microbial – Photolytic Lakewide Horizontal Dissipation
SouthSouth TwinTwin Lake,Lake, 20102010 Mean Treated 2,4-D Herbicide Residuals 2500 2,4-D Herbicide Concentrations Mean Untreated Lakewide Target Irrigation Limit
) 2000
Lae
/
µg
( 1500
1000
Concentration 500
0 0 7 14 21 28 35 42 Days after treatment Lakewide Vertical Dissipation
Mixed Lake
Stratified Lake Lakewide Vertical Dissipation
ForestForest Lake, Lake 2,4 2,4-D-D Herbicide Herbicide Concentrations Residuals
350 5 ft 300 10 ft 15 ft 250 20 ft 25 ft 200 Target Conc.
150
100
Concentration (µg/L ae) (µg/L Concentration
50
0 0 7 14 21 28 35 Days after treatment Survey Methods
Herbicide Water Sample Collection
Immunoassay Test (ELISA)
Aquatic Plant Surveys – Hauxwell et. al 2010 Large-Scale Milfoil Control
100 Grass Wilson South Twin '10 Tomahawk Deep Pine 90 Big Sand Sandbar '11 Sandbar '13 Kathan 80
70 EWM Forest '11 60 Forest '12 HWM 50 South Twin '09 English '10 Round
40 Frog Golden George Silver Milfoil Control (%) Control Milfoil 30
20 English '12
10 Marion Millpond 0 Langford 0 0.1 0.2 0.3 0.4 0.5 0.6 Mean 2,4-D Concentration 0-7 DAT (ppm) Watermilfoil DNA Analysis
LaRue et al. 2014
Zuelling & Thum, 2012 Large-Scale Milfoil Control
100 Grass Wilson South Twin '10 Tomahawk Deep Pine 90 Big Sand Sandbar '11 ??? Sandbar '13 High level of milfoil Kathan control 80 Focus Seasonal area Damage to natives 70 milfoil control EWM Damage to Forest '11 60 Forest '12 HWM No control some natives 50 South Twin '09 English '10 Round
40 Frog Golden George Silver Milfoil Control (%) Control Milfoil 30
20 English '12
10 Marion Millpond 0 Langford 0 0.1 0.2 0.3 0.4 0.5 0.6 Mean 2,4-D Concentration 0-7 DAT (ppm) Pre/Post Native Species * = negative 2,4-D Whole Lake Treatments + = positive Scientific Name, Common Name Group Sandbar Tomahawk Frog Kathan S. Twin '09 S. Twin '10 Berry Wilson Myriophyllum spicatum , Eurasian water milfoil Dicot *** *** n.s. *** *** *** *** *** Bidens beckii , Water marigold Dicot - <5% - - *** *** - - Brasenia scherberi , Watershield Dicot - <5% - n.s. - - n.s. <5% Ceratophyllum demersum , Coontail Dicot <5% <5% - n.s. n.s. n.s. <5% *** Chara spp., Muskgrasses Macroalgae n.s. n.s. n.s. n.s. *** n.s. n.s. * Eleocharis acicularis , Needle spikerush Monocot n.s. <5% - <5% n.s. n.s. <5% <5% Elodea canadensis , Common waterweed Monocot n.s. *** - n.s. n.s. *** <5% n.s. Heteranthera dubia , Water star grass Monocot - <5% - - *** * - - Myriophyllum tenellum , Dwarf watermilfoil Dicot n.s. <5% - - <5% - <5% - Myriophyllum sibiricum, Northern watermilfoil Dicot - <5% - <5% *** *** ** <5% Najas flexilis , Bushy pondweed Monocot ** *** *** *** n.s. *** * * Nitella spp., Stoneworts Macroalgae n.s. *** - *** <5% <5% <5% n.s. Nymphaea odorata , White water lily Dicot - <5% <5% n.s. - - <5% n.s. Potamogeton amplifolius , Large-leaf pondweed Monocot n.s. *** n.s. n.s. <5% <5% n.s. n.s. Potamogeton epihydrus , Ribbon-leaf pondweed Monocot - - - *** - - - <5% Potamogeton foliosus , Leafy pondweed Monocot - - * - - - - - Potamogeton friesii, Fries' pondweed Monocot - - - - ** <5% - - Potamogeton gramineus , Variable leaf pondweed Monocot * n.s. <5% <5% n.s. * n.s. - Potamogeton pusillus , Small pondweed Monocot *** *** n.s. *** * *** <5% ** Potamogeton richardsonii, Clasping-leaf pondweed Monocot <5% - - <5% + n.s. - - Potamogeton robbinsii , Robbins pondweed Monocot n.s. * - - n.s. n.s. n.s. *** Potamogeton strictifolius , Stiff pondweed Monocot - - *** *** <5% <5% <5% - Potamogeton zosteriformis , Flat-stem pondweed Monocot - - n.s. + n.s. *** <5% *** Stuckenia pectinata , Sago pondweed Monocot - - n.s. - - - <5% - Utricularia minor , Small bladderwort Dicot - - - * - - - - Vallisneria americana , Wild celery Monocot *** *** <5% + *** + + *
Native spp. Significant Decrease (FOO > 5%) 4 7 3 6 7 8 2 7 Native spp. Significant Increase (FOO > 5%) 0 0 0 2 1 1 1 0 Net Native spp. Loss/Gain -4 -7 -3 -4 -6 -7 -1 -7 Macrophyte Community
Tomahawk
Sandbar
Tomahawk
Sandbar
Nault et al., 2014. Lake & Res. 30:1-10 Tomahawk/Sandbar
Nault et al., 2014. Lake & Res. 30:1-10 2,4-D Herbicide Monitoring
Nault et al., 2014. Lake & Res. 30:1-10 What variables affect herbicide degradation rates?
Half-life = 36 days Half-life = 6 days Lake type? Water chem (pH, cond, TSI)? Water temp? Treatment history? 2,4-D Concentration/Exposure Time Small-Scale ‘High’ dose Green & Westerdahl, 1990 Short exposure JAPM 28:27-32 2.0
1.5
ae ppm 1.0
0.5
Recommended 2,4-D label rate: 2.0 – 4.0 ppm (Hours) 1.0 ppm = 1.0 mg/L = 1000 ppb
Preliminary Findings
• Recommended 2,4-D label concentrations (2.0-4.0 ppm) may not be applicable for whole lake or large scale chemical treatments • Treating multiple ‘small’ areas of a lake can result in a whole lake treatment if the scale of the treatment area is large compared to the overall lake volume • EWM control looks promising, however short-term damage to certain native species may occur and long-term effects on biotic and abiotic parameters is uncertain • Further exploration of hybrid milfoil populations is needed • Small scale treatments undergo rapid dissipation and efficacy is less predictable • Herbicide monitoring is important, both to understand treatment efficacy, as well as ecological risks DISCUSSION
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