Upload
hoangdat
View
216
Download
0
Embed Size (px)
Citation preview
Weed Control with Herbicides
in Alaska: Some Concerns
Steven Seefeldt
Mean Farm Size in the USA
100
200
300
400
500
1850 1870 1890 1910 1930 1950 1970 1990
Acre
s
Year
Weed Control is the Key
• 1731 – Jethro Tull wrote Horse Hoeing
Husbandry
– Plant crops in rows
– Use horse drawn hoe to weed
– Use fertilizers (horse manure) to enhance
crop growth
• He developed farm equipment, started
research, and wrote widely
• By early 1970’s was a band with a flute…
Weed Control Classification
• Physical
• Cultural
• Biological
• Chemical
Weed Control Classification
• Physical
• Hand pulling and
hoeing
• Fire
• Flame
• Tillage/Disturbance
• Mowing and
Shredding
• Chaining and
Dredging
• Flooding
• Mulching and
Solarization
Weed Control Classification
• Cultural
• Prevention
• Crop rotation
• Competition
• Smother crops
• Living mulches
and cover crops
• Harvesting
Weed Control Classification
• Biological
• Grazing
• Mycoherbicides
• Allelopathy
Weed Control Classification
• Chemical
• Herbicides
Pesticides
• Herbicides
• Fungicides
• Insecticides
• Rodenticides
• Biocides
• Etc.
Toxicology
• Caution
• Warning
• Danger
Before the scientific method and
hypothesis testing
What did hunter gathers do?
One Several Dinner
Tasty Tasty Filling
What did hunter gathers do?
One Several Dinner
Tasty Tasty Filling
Tasty Tasty Stomach
ache
What did hunter gathers do?
One Several Dinner
Tasty Tasty Filling
Tasty Tasty Stomach
ache
Stomach Dead Still Dead
ache
Log-logisitic equation
y=C+
D = Upper limit C = Lower limit b = Related to slope I = Dose giving 50% response
D-C 1+exp[b(log(x)-log(I ))] 50
50
Seefeldt et al. 1995
Dose-response curve
0.01 0.1 1 10 100 0
20
40
60
80
100
Herbicide Dose
Perc
en
t of contr
ol Upper limit (D=100)
I50
Lower limit (C=4)
Treatment comparison
0.01 0.1 1 10 100 0
20
40
60
80
100
Herbicide Dose
Perc
en
t of contr
ol Upper limit (D=100)
I50
Lower limit (C=4)
I50
Treatment comparison
0.01 0.1 1 10 100 0
20
40
60
80
100
Herbicide Dose
Perc
en
t of contr
ol Upper limit (D=100)
I50
Lower limit (C=4)
I50
Factors affecting pesticide fate
Volatilization Photodecomposition Plant uptake
and removal
Microbial degradation
Absorption
Chemical degradation
Leaching
Runoff
How do herbicides kill plants?
• Basically it is a chemical reaction
2,4-D Roundup
Paraquat Garlon Glean
What Roundup (glyphosate) does
Chorismate is
turned into one of
the three aromatic
amino acids
What Roundup (glyphosate) does
What Roundup (glyphosate) does
Sheep + Plateau
Plateau only Sheep only
Control
Biological + Chemical
Physical + Chemical
Fate of Herbicides
• The half life
• The time it takes to lose half the herbicide
Fate of Herbicides
• The half life
• The time it takes to lose half the herbicide
• For 10 day half life
• Day 0 100%
• Day 10 50%
• Day 20 25%
• Day 30 12.5%
• Day 40 6.3%
• Day 50 3.2%
• Day 60 1.6%
Fate of Herbicides
• The half life
• The time it takes to lose half the herbicide
• For 10 day half life
• Day 0 100%
• Day 10 50%
• Day 20 25%
• Day 30 12.5%
• Day 40 6.3%
• Day 50 3.2%
• Day 60 1.6%
Herbicide fate
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
Days
% o
f h
erb
icid
e
Fate of Herbicides
• Photo-decomposition (treflan)
Fate of Herbicides
• Photo-decomposition (treflan)
• Adsorption (paraquat)
Fate of Herbicides
• Photo-decomposition (treflan)
• Adsorption (paraquat)
• Plant metabolism (tolerant versus
susceptible plants)
Fate of Herbicides
• Photo-decomposition (treflan)
• Adsorption (paraquat)
• Plant metabolism (tolerant versus
susceptible plants)
• Chemical (soil and weather dependent)
Fate of Herbicides
• Photo-decomposition (treflan)
• Adsorption (paraquat)
• Plant metabolism (tolerant versus
susceptible plants)
• Chemical (soil and weather dependent)
• Microbial decomposition (most important)
Environmental Influences
• Soil pH – it depends on the herbicide
• Soil organic matter – adsorbs herbicide
• Clay – adsorbs most herbicides
• Soil chemistry – hard to separate microbes
• Cold – slows breakdown
• Dry – slows breakdown
Fate of Triclopyr
Results: Delta Junction CRP
0-5 cm
15-15 cm
15-30 cm
Soil froze about
110 DAT and
thawed about
276 DAT
A comparison of herbicide extraction
from the soil and a bio-assay
0
20
40
60
80
100
120
0.01 0.1 1 10
Triclopyr concentration (kg ai/ha)
Bio
mass a
s p
erc
en
t o
f co
ntr
ol
1 DAT 3 DAT
7 DAT
21 DAT
35 DAT
283 DAT
365 DAT
Fate of 2,4-D and Glyphosate
• Similar to triclopyr with normal breakdown
rates in the growing season, but cessation
when soils freeze
Aminopyralid and Clopyralid
Use in Alaska • Control of invasive weeds
• Spot spraying for perennial sowthistle
• Control of orange hawkweed and narrowleaf
hawksbeard in pastures and hay fields
Background
• Aminopyralid and Clopyralid
– Both are synthetic auxins
• Auxin is a plant hormone
– Involved in cell division
– Involved in cell growth
• Auxins move in the phloem to the growing points
Background
• Aminopyralid and Clopyralid
– Both are synthetic auxins
• Auxin is a plant hormone
– Involved in cell division
– Involved in cell growth
• Auxins move in the phloem to the growing points
– Both control orange hawkweed and
narrowleaf hawksbeard
Background Clopyralid
• Discovered 1961
• Sold in 1978 in Europe
• Sold in 1987 in US
• Curtail, Stinger, Confront
Background Clopyralid
• Discovered 1961
• Sold in 1978 in Europe
• Sold in 1987 in US
• Curtail, Stinger, Confront
• Now off patent
• Post emergence in pasture, rangeland,
and CRP
• Half life 12-70 days – microbial
Background Aminopyralid
• Sold as Milestone
• Still on patent
• Expensive
• Sold about 2005
Background Aminopyralid
• Sold as Milestone
• Still on patent
• Expensive
• Sold about 2005
• Used in rice, pastures rangeland, ROW,
wheat, oil palm, and rubber plantations
• Half life 25 to 35 days (averages)
• Photodegradation then microbial
Orange Hawkweed Study
• Five sites, Talkeetna and
Homer
• Plots 6 x 30 feet
• Three herbicides at three
rates (1, ½, and ¼ the full
rate plus a control)
• Three replications of each
of the above treatments
• Randomized complete
block
2007 Field Trials
Pre-treatment Measurements:
• Two ¼ x ¼ m sub-plots per plot
• % cover estimates of orange
hawkweed, grasses, and forbs
Post-treatment Measurements:
• Rate plots visually based on
herbicide damage, 0% (no damage)
to 100% (dead) after three weeks
• End of season harvest ¼ x ¼ m
sub-plots and separate by cover
type
• Rate plots visually the following year
Visual Injury - Milestone
0
10
20
30
40
50
60
70
80
90
Perc
en
t in
jury
0.125 0.25 0.5 1
Herbicide rate (1 = 0.12 kg/ha)
C
A A
B
The Work in Homer, AK
Control area
Biomass harvest Milestone 1x
Visual Injury - Transline
0
10
20
30
40
50
60
70
80
Perc
en
t in
jury
0.25 0.5 1
Herbicide rate (1 = 1.1 kg/ha)
B
AB
A
Impact on Grasses
0
50
100
150
200
250
300
350
Perc
en
t d
ry w
eig
ht
0.125 0.25 0.5 1
Herbicide rate
Milestone Redeem Transline
Impact on Other Plants
Milestone Redeem Transline
----------------- % injury -----------------
Dandelion 100-72 98-83 81-73
Clover 100-53 100-80 73-57
Yarrow 25 100-50 70-50
Geranium 0 100 -
Some Label Restrictions
Example of Injury, Raised Beds
Marigolds Potatoes Tomatoes
Injury 2 Years After Spot Spray
Unexpected Injury, Potatoes
Carry Over Research Design
H1 H2
H3 H4
H5 H6
• Six treatments
– Control
– Glean 75DF (0.33 oz/A)
– Ally 60DF (0.1 oz/A)
– Banvel (3 fl oz/A)
– Stinger (0.33 pt/A)
– Milestone (7 fl oz/A)
• Applied the summer of 2011
Carry-Over Weed Injury – Palmer
Weed Control Aminopyralid Clopyralid
Plants per meter square
Chickweed 48 2 74
Corn Spurry 89 3 166
NL Hawksbeard 668 0 11
Dragonhead 24 0 1
Lambsquarters 54 1 27
Pineapple Weed 8 0 0
Shepherd’s Purse 504 0 11
Total 1,395 6 290
Dose-Response Research Design 1X glean
0.5X glean
0.25X glean
0.125X glean
0.062x glean
No herbicide
Barley Canola Potato Lettuce Carrot Kale Nocrop
Visual Injury – Dose Response
Aminopyralid Clopyralid
Potato Response Above Ground
0
20
40
60
80
100
0 0.06 0.125 0.25 0.5 1
% o
f co
ntr
ol
Aminopyralid dose (1 = 7 fl oz/A)
Delta
Fairbanks
Palmer
0
20
40
60
80
100
0 0.06 0.125 0.25 0.5 1
% o
f co
ntr
ol
Clopyralid dose (1 = 0.33 pt/A)
Visual Injury – Crop + Weed
Aminopyralid Clopyralid
The Weed as a Bio-assay
• Can we use weeds to estimated herbicide
residuals?
• What are potential problems?
0
10
20
30
40
50
60
70
80
90
100
0 0.06 0.125 0.25 0.5 1
% o
f c
on
tro
l
Aminopyralid rate (1 = 7 fl oz/A)
Delta
Palmer
Milestone D
Milestone P
Potato
Crepis
Potato Response Below Ground
0
5
10
15
20
0 0.06 0.125 0.25 0.5 1
Po
tato
harv
est
(lb
)
Aminopyralid dose (1 = 7 fl oz/A)
Delta Palmer
0
5
10
15
20
0 0.06 0.125 0.25 0.5 1P
ota
to h
arv
est
(lb
)
Clopyralid dose (1 = 0.33 pt/A)
Is there Herbicide in the Tuber?
Is there herbicide in the tuber?
• Tubers were sent to the Montana
Department of Agriculture Laboratory at
Montana State University to extract the
herbicide
• Dr. Rick Boydston with ARS in Prosser,
WA funded the work ($150/sample)
Extraction Results
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0 0.06 0.125 0.25 0.5 1
Am
ou
nt
ex
tra
cte
d (
pp
m)
Aminopyralid rate (1 = 7 fl oz/A)
Delta
Palmer
Is that Herbicide Herbicidal?
Is that Herbicide Herbicidal?
Aminopyralid
Is that Herbicide Herbicidal?
clopyralid
Conclusion
• Aminopyralid and clopyralid management
– Their residues are in the plant and soil
– They pass through ruminants unchanged
– They will accumulate in potato tubers
– Some plants are more sensitive than others
– There are potential bioassays
– Half lives are currently unknown
Conclusion
• Other herbicides
– In the growing season several herbicides
breakdown at rates estimated in the literature
– When soils are frozen herbicide breakdown
ceases
– Therefore, overall herbicide half-lives are
extended in Alaska, particularly in the interior
Questions