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TVMA Annual Meeting
October 9, 2015
Bill Kline, Dow AgroSciences – Retired
William N Kline, LLC Ball Ground, GA
REASONS HERBICIDE APPLICATIONS
SOMETIMES FAIL
3
Solutions for The Growing World
Why Is It Important to Understand Why
Herbicides Sometimes Don’t Work?
| 4
Factors Affecting Herbicide Performance
Controllable
Uncontrollable
| 5
Factors Affecting Herbicide Performance
Controllable
•weed ID – know the target weeds
• plant size and stage of growth
• herbicide selection
• adjuvant/surfactant selection
• water quality
• mixing (compatibility)
• application technique
•weather/environment (somewhat)
• herbicide resistance (somewhat)
Uncontrollable
• weather/environment
• herbicide resistance
| 6
Impacts of Drought:
• Plant reactions to drought are natural and actually work against the efficacy of herbicides
• Cuticle thickness becomes a greater barrier to herbicide entry
• Plant growth slows down – herbicide does not translocate throughout the entire plant: foliage, stems and roots.
Weather
| 7
Plant Responses to Drought
• Stomata on leaf surface close to reduce water loss
> Reduces herbicide uptake
• Leaves wilt, curl, or droop
> Impacts coverage and adhesion
• Leaves may develop thicker cuticle
> Impacts herbicide penetration
| 8
Plant Responses to Drought
| 9
So…….. What to do if you are experiencing drought
conditions?
• First question that we always ask. Is it possible to delay the herbicide
application?
• Sometimes, just wait for a decent rain event.
• Increase herbicide rate
• Increase total carrier volume (water carrier volume)
• Increase or change the surfactant/adjuvant
• Accept less weed control than you expect – this may happen even
with the options above.
| 10
Drought Impacts on Bareground
Rain required to activate
http://www.dowagro.com/vm/
| 11
Impacts of Rain
• Pay attention to weather forecast
• Know capabilities and limitations of herbicides
• Check product information for rainfastness
12
Solutions for The Growing World
Improper Weed Identification, Rate,
Application Timing, and Adjuvant
| 13
Misidentification
leafy spurge Canada goldenrod
“But I thought it was…………”
| 14
Identifying Weeds From Pictures
“What is this?”
With camera phones and tablets
weed identification hasn’t become
any easier. Poor focus and lack
of detail on key plant structures
makes ID difficult on uncommon
species.
| 15
Identifying Weeds
Making your pictures count
• Leaf shape and arrangement
• Pubescence, petiole, stem
• Flower detail
Accompanying information
• Location
• Site characteristics (wet or dry)
• Height at maturity
http://www.dowagro.com/vm/
| 16
Proper Plant Identification
| 17
Proper Plant Identification
Walnut Ailanthus
| 18
Application Timing – Label Statements
• “For annual weed control best results are generally achieved when
applied to young, actively growing weeds”
> Germinate from seed , produce seed and die within one year
> Ragweed, pigweeds
| 19
Annual Weeds
Emerge Vegetative growth Flower Mature
| 20
Application Timing – Label Statements
• “For perennial weed control best results are generally achieved when
applied during the vegetative/bud/bloom stage or fall rosette stage”
> Perennial weeds: Emerge from rootstock, produce seed, go dormant (last
more than 2 years)
> Canada thistle, ironweed, dog fennel, woody plants, etc.
| 21
Perennial WeedsVegetative regrowth
after mowing or
development of a
rosette as with thistles,
etc.
| 22
Know Labeled RatesRate
| 23
Know Label Recommendations – read footnotes under tables
| 24
Application Timing
Biggest issues
• Manpower – “we want to target optimum timing but logistics and available
manpower sometimes gets in the way…”
Use Higher Rates; change application method; change herbicide mixtures:
• Hard to control species are prevalent
• Weeds in advanced stages of growth
• Less than favorable growing conditions exist
| 25
Root to Shoot Ratio
| 26
Foliar Applications Too Early
| 27
Foliar Applications Too Late
• Foliar applications lose
effectiveness as the fall season
begins – depends on the herbicide
being prescribed; consider
alternative herbicide mixtures.
| 28
Cultural Considerations
Reduced control may result when
plants:
• Recently mowed, grazed, or cut
(pre or post app)
• Not allowed to re-grow to
recommended stage for treatment
| 29
Use of Adjuvants/Surfactants
Most herbicides require a particular adjuvant, surfactant or diluent.
Generally most important for foliar applications!
• Considerations
> Type of leaf: waxy or hairy
> Leaf interception
> Post-impact drop behavior
• Spend some time learning about these products – lots of changes and improvement in recent years.
• Read product labels for specific adjuvant recommendations
| 30
Effect of adjuvants on droplet behavior on leaves
Waxy leaf
Hairy leaf
Droplet evaporation and spread on waxy and hairy leaves associated with type and concentration of
adjuvants Linyun Xu,a Heping Zhu,b∗ HErdalOzkan,c William E Bagleyd and Charles R Krauseb
| 31
| 32
| 33
| 34
35
Solutions for The Growing World
Sprayer/Equipment Calibration
| 36
Sprayer Calibration
“Can’t you just tell me how much to put in my 100 gallon sprayer?”
Purpose
• Deliver specified rate per acre
Frequency
• More frequent the better
• Visually check nozzles before every use
• Knowing the nozzle output at a given pressure doesn’t mean it will
always be that way
> Corrosion
> Bad gauges
> Pressure drop between the gauge and the nozzles
37
Solutions for The Growing World
Water Quality
| 38
Impacts of Water Quality
• Turbidity – when suspended solids (silt, clay, other organic matter)
floating in water
> Some herbicides bind to particles suspended in water = less available for
target plant(s) example - glyphosate
• Water hardness – all water sources in nature contain dissolved minerals
such as calcium, magnesium, and iron.
> Herbicide molecules attach to positively charged mineral molecules (cations)
in hard water = less available for target plants
> Label should provide warnings if water hardness is a potential problem for a
given herbicide.
• Water pH – very acid or very alkaline water can increase the rate of
herbicide degradation in the tank; generally not a problem in the SE.
Source: Purdue University Extenion,“The Impact of Water Quality on Pesticide Performance” PPP-86
39
Solutions for The Growing World
Improper Mixing & Incompatibility
| 40
Mixing Herbicides
• Read label for special instructions
• Check for compatibility
Example from Garlon 3A label: “If tank
mixing with Rodeo herbicide, mix the
Garlon 3A with at least 75% of the total
spray volume desired and ensure that
Garlon 3A is well mixed before adding
the Rodeo to avoid incompatibility.”
41
Solutions for The Growing World
What Can Happen During Application
| 42
Impacts of Spray Drift
• Off-target movement of spray
droplets
Non targetDrift
Target Area
| 43
Improper Coverage
• Brush height and density impact volume needed and proper application method
| 44
Inadequate Spray Pattern
45
Solutions for The Growing World
When Individual Plant Treatments
Go Wrong
| 46
When Basal Bark Treatments Don’t Work
• Didn’t treat completely around each
stem
• Didn’t treat stem at all (common
problem at higher stem densities)
• Stem too large (or thick corky bark)
• Basal mixture not properly mixed
and agitated
• Exposed roots not treated
| 47
When (Water Based) Cut Stump Treatments
Don’t Work
• Didn’t treat immediately after cutting
> Remember “Seconds Count”
• Didn’t treat entire cambium/outer 2 inches
• Treated cut surface when covered with saw
dust or other debris
• Cut and treated during heavy sap flow
| 48
Cut Stump Treatments
• Treat entire cambium/outer 2 inches of sapwood
| 49
Cut Stump Treatments
• Treat entire cambium/outer 2 inches of sapwood
| 50
When Oil Based Cut Stump Treatments Don’t
Work
• Treated wet bark – turns milky
• Didn’t treat entire cambium/outer 2
inches, exposed bark, & root flares
• Treated cut surface when covered with
saw dust or other debris
• Mixture not properly mixed or agitated
| 51
Hack & Squirt Treatments
• Cuts about 2 inches apart for most species
• Angle cuts downward - 45 degrees
• Cut must penetrate into sapwood
• Fill each cut (about 1 pull) but not to the point of running out of “cup”
• Apply mixture immediately to the cut
| 52
When Hack & Squirt Treatments Don’t Work
• Cut not angled properly to “hold”
mixture
• Cuts too far apart
• Not enough mixture applied
• Cuts not deep enough to allow mixture
to enter cambium/sapwood
• Diluted mixture not properly agitated
| 53
Making a Multi-year Commitment
• Some species require multiyear applications
| 54
Reasons herbicide Applications Sometimes Fail
• Hopefully this review has provided you with some “food for thought” on
things that can go wrong with herbicide applications.
• And, hopefully this review will help you to reduce you chances of
reduced efficacy or herbicide failure.
55
Solutions for The Growing World
Questions?
56
Solutions for The Growing World
| 57
Low Volume Basal Bark Treatments
• One of the most versatile
treatments
• Performed anytime of year
except when bark is wet
• For trees and brush <6” in
diameter
Autumn Olive, Granite City, IL. Garlon 4 Ultra @ 25% + Bark Oil Blue LT @ 75%
| 58
Hack and Squirt Treatments
Doing a “hack” job
| 59
Coverage
“But then I’ll have to fill up again”• Aerial: 5 gpa
• Ground broadcast: 15 gpa
• IPT and Directed: ?????
| 60
Choosing the Right Broadcast Equipment• Boomless vs. Boom
> Overlaps are of concern for certain brush and tree species
> Some herbicides shouldn’t be overlapped
• Max rate being applied
• Grass damage
| 61
The Following Video Clips come from:
Midwest Area Home / Application Technology Research Unit / Services /
Evaporation and spread of surfactant-amended droplets on leaves
USDA ARS
Heping Zhu
| 62
Recommended Guides Based on Water pH:
• A higher or lower than optimal pH causes some herbicides to begin
degrading
• pH 3.5 – 6 satisfactory for most spraying and short-term (> 1 day)
storage of mixtures
• pH 8-9 adequate for immediate spraying for most herbicides. Most
products mixed in alkaline water should be sprayed the same day.
• Label should provide warnings if pH is a potential problem for a given
herbicide.
Source: Purdue University Extenion,“The Impact of Water Quality on Pesticide Performance” PPP-86
| 63
Cut Surface Treatments
Water Based Treatment
• Applied < 1hr after cutting
•Remember “Seconds Count”
• Can perform all year except during
heavy sap flow
• Apply to cambium/outer 2 inches
Oil Based Treatments
• Applied up to several weeks after cutting
• Perform all year except when bark wet
• Applied to cambium/outer 2 inches,
outer bark, and root flares
| 64
Matching Application Method and Nozzles to Target
Species Height and Density
| 65
Leaf Structure & Terminology