Aquatic Herbicide Application Considerations

BILL HALLER AND RHETT GEHRING MATERIAL BORROWED (STOLEN) FROM FRED FISHEL UF CENTER FOR AQUATIC PLANTS

Foliar Applications

Glyphosate efficacy is affected by:  Amount of diluent  pH and Hardness  Fe++, Ca++, Mg++  Turbidity  Adjuvant  Flooding  Time of year  Humidity  Tank mix partners Dilutent, Humidity, Adjuvant Diluent pH, Hardness, Ca++, etc.

 Interrelated  Complicated

 Very Relevant pH (-Log H+)

 Complicated Chemistry  Changes Daily-Pts

 Florida Lakes = 5-9  Stomach = 2.0  Beer = 3.5  Milk = 6.5  Soap = 9 ph

pH 5 pH 9 CO2 CO3

SO4 Mg

Fe+ Ca

Tannic Acids Fe++

CO2 - HCO3 - CO3

What does an applicator do? Distilled water?

 Well water or Lake water?

 Additives? Diurnal pH

6 Hydrilla Mat Open Water 5

4 7AM 9AM 11AM 1PM 3PM 5PM 7PM 9PM 11PM 1AM 3AM Hardwater (Ca) study

% Absorbed 4hr 48hrs Glyphosate 22.4 32.5

Glyphosate + Ca 4.9 6.5

Glyphosate + Ca + AMS 21.9 25.3

What is AMS?

Thelen, K.D. 1995 Weed Science 43:541-548 Old Glyphosate Label

 “For improved control of stressed plants add 1-2% (8.5-17 lbs) of ammonium sulfate to the tank mix.” What about turbidity?

 Why does glyphosate not control submersed?

 Why can you use glyphosate at base of trees?

 Would you use imazapyr at base of trees? Glyphosate Label

“Reduced results may occur if tank mixed with water containing organic matter, suspended solids, clays. ect.”

WHY? Koc=24,000 Mg/L

Diquat = 1,000,000 Mg/L Endothall = 150 Mg/L Imazapyr = 348 Mg/L

Torpedograss – Panicum repens Why does glyphosate not control submersed? • Diluted greatly, Ca++. Mg++, organic matter, clays, then microbes

Why can you use glyphosate at base of trees? • Held in very top of soil (High Koc)

Would you use imazapyr at base of trees? • Very low Koc = root uptake Time of year?

 Xylem = Unidirectional, upward movement from roots to shoots, nutrients and water.

 Phloem = Multidirectional, moves sugars (and Glyphosate) throughout the plant. Tank mixing is all the rage!

 Antagonistic 2+2=1  Additive 2+2=4  Synergistic 2+2=7

Mathematical models determine this

 Diquat and copper (hydrilla)  Endothall and copper (hydrilla)  Diquat and glyphosate (torpedo)  Flumioxazin and glyphosate (ludwigia) Back to glyphosate

“Tank mixing with paraquat (diquat), phenoxy and other auxin type herbicides may reduce glyphosate activity.” (Herbicide Handbook). Other aquatics affected by pH

 2,4-D Amine  2,4-D Ester Just works better at lower pH

 Flumioxazin (Clipper)  pH in diluent (in tank) Foliar Applications

 Herbicide Selected  Dilutent  pH  Hardness  Fe++  Turbidity  Adjuvant 1

 Time of Year  Flooding  Rainfall  Temperature/Humidity

Torpedograss/Glyphosate/Rainfall % Green Tissue

120

100 LSD = 7% 80

% 60

0 0 3 6 12 24 48 72 96 192 Rain Submersed Treatments Successful weed control depends on…

 Weed, growth stage  Herbicide, contact or systemic  Exposure time, half-life  Formulation, granular or liquid  Size of treatment area  Water flow  Application method

?Whole Lake Application?

 1 ppm in 1 million pounds of water = 1lb AI  Acre foot of water = 2.7 million pounds  1 ppm in 1 acre foot = 2.7 pounds AI

 1.5 Acre pond, 10 feet deep = 15 acre feet  1 ppm of endothall = 15 acre feet x 2.7lb A ft =40.5lbs AI (10 gallons)

?Whole Lake application?

 1 ppb in 1 million pounds of water = 0.001 pounds AI  1 ppb in 1 acre foot = 0.0027 pounds AI

 1.5 acre pond, 10 feet deep = 15 acre feet  1ppb of endothall = 15 acre feet x 0.0027 pounds/A ft = 0.0405 lbs AI (1.3 oz)

ppb = Flumioxazin, Penoxsulam, Fluridone, Bispyrabac, Topramezone Golden Rule

 Contact-Exposure Time (CET)

 A herbicide must be in high enough concentration for at least a critical time in order to kill submersed plants Milfoil – endothall (Netherland JAPM 1991) General Exposure Requirements

Diquat Minutes to Hours Copper Minutes to Hours Flumioxazin Minutes to Hours Endothall Hours to Days

Fluridone 45+ Days Topramezone 45+ Days Penoxsulam 45+ Days Bispyrabac 45+ Days Size of treatment area

1 Mile ling strip 40 ft wide: = 5 Acres

= 5,280 ft / 5 Acres

= > 1,000 ft / Acre

Treatment area (green) 40’ wide strip 1 mile long VS.

 Square:

Treatment area (green) 4 sides @ 466’ per side

 = 466 ft x 4 sides = 1,864 ft / 5 acres  = < 400 ft / acre Granular vs. Liquid

Growing points

Justification for use

 Granule will sink below the thermocline

 Allows an extended release of the herbicide?

 Prevents rapid loss in moving water?

Static

120 110 100 90 y= 113.7 (1-e-1.17x), r2= 0.95 80 70 60 50 40 30 20 10

Percent of triclopyr released from OTF granules OTF from released triclopyr of Percent 0 0 5 10 15 20 25 Time (days) Aerated

110 y= 103.6 (1-e-14.14x), r2= 0.83 100 90 80 70 60 50 40 30 20 10

Percent of triclopyr released from OTF granules released of Percent triclopyr 0 0 5 10 15 20 25 Time (days)  Estimated time (hours) required for 25, 50, 75 percent of triclopyr and endothall to release from Renovate OTF and Aquathol Super K granules maintained under static and aerated conditions.

Herbicide ET25 ET50 ET75 Triclopyr Static 5 12 22 Endothall Static 38 87 155 Triclopyr Aerated 0.5 1.2 2.3 Endothall Aerated 0.5 1.1 2.1 Static

120 -0.02x 2 Sonar Q y= 121.3 (1-e ); r = 0.87 -0.04x 2 110 Sonar PR y= 66.5 (1-e ); r = 0.95 -0.03x 2 100 Sonar ONE y= 73.3 (1-e ); r = 094 -0.02x 2 Sonar SRP y= 70.4 (1-e ); r = 0.89 90 Sonar Q Sonar PR 80 Sonar ONE Sonar SRP 70

Percentof fluridone released from granule Sonar 0 0 10 20 30 40 50 60 70 80 90 100 110 120 Time (days after treatment) Aerated

120

110

100

60 -0.06x 2 Sonar Q y=86.3 (1-e ); r =0.94 50 -0.22x 2 Sonar PR y=91.4 (1-e ); r =0.72 40 Sonar ONE y=89.0 (1-e-0.15x); r2=0.84 Sonar SRP y=103.8 (1-e-0.12x); r2=0.90 30 Sonar Q Sonar PR Sonar ONE 20 Sonar SRP 10

Percent of fluridone released from Sonar granule Sonar from released fluridone of Percent 0 0 10 20 30 40 50 60 70 80 90 100 110 120 Time (days after treatment)

Sediment

100 y=22.9 (1-e-0.06x); r2=0.81 90

10 Percent of Fluridone Released from Q Sonar Released of Percent Fluridone 0 0 10 20 30 40 50 60 70 80 90 Days After Treatment Sediment

100 y=87.8 (1-e-0.10x); r2=0.91

Percent of Endothall Released from of K Super Percent Aquathol Endothall Released 0 5 10 15 20 25 30 Time (days after treatment) Granules or Liquid?

 Careful of sediment

 Water movement changes release

 Nothing magical about granules

 Justify cost??? The End