Kurt Hembree – March 11, 2015
PAPA Seminar
March 11, 2015
Kurt Hembree
Weed Management Farm Advisor, Fresno County
Weed Resistance
Management in the
Southern SJV
“Diversity and proactive
weed management is the
only way farmers are going
to survive this thing –
herbicide resistance.” From the Global Herbicide Resistance Challenge Conference, 2013
Kurt Hembree – March 11, 2015
Resistance vs. Tolerance:
Resistance: “The inherent ability of a weed to survive and
reproduce following exposure to a dose of herbicide
normally lethal to the wild type”. (WSSA)
The herbicide once worked at label rates, but now it doesn’t.
Tolerance:
“The inherent ability of a weed to withstand the specific
effects of a particular herbicide”. (WSSA)
The herbicide never really worked brfore.
Kurt Hembree – March 11, 2015
How selection for resistance occurs:
Kurt Hembree – March 11, 2015
► Altered target site
► Enhanced metabolism
► Compartmentalization or sequestration
► Overexpression of target protein
► Altered translocation
► Gene amplification
Mechanisms of resistance:
Target site is no
longer susceptible
to the herbicide.
Kurt Hembree – March 11, 2015
Glyphosate-resistant fleabane Glyphosate-resistant ryegrass
Glyphosate-resistant junglerice
Kurt Hembree – March 11, 2015
Weed biotype - CA Situation Herbicide family Year
Common groundsel Asparagus PS II 1981
Perennial ryegrass RR, Roadside ALS 1989
Smallflower umbrella sedge Rice ALS 1993
California arrowhead Rice ALS 1993
Russian thistle Roadside ALS 1994
Wild oat Barley, Wheat Pyrazoliums 1996
Redstem Rice ALS 1997
Ricefield bulrush Rice ALS 1997
Late watergrass Rice ACCase and Lipid syn. 1998
Rigid ryegrass Almond Glycine (glyphosate) 1998
Long-leaved loosestrife Rice ALS 2000
Barnyardgrass Rice ACCase and Lipid syn. 2000
Early watergrass Rice ACCase and Lipid syn. 2000
Littleseed canarygrass Onion ACCase 2001
Smooth crabgrass Rice Synthetic Auxins 2002
Horseweed T&V, Roadside Glycine (glyphosate) 2005
Hairy fleabane T&V, Roadside Glycine (glyphosate) 2007
Hairy fleabane T&V, Roadside Glycine (glyphosate) and Bipyridiliums (paraquat) 2009
Junglerice Corn, Alfalfa, T&V, Roadside Glycine (glyphosate) 2011
Kurt Hembree – March 11, 2015
Other weeds to watch out for:
► Palmer amaranth, Lambsquarters, (glyphosate)
► Junglerice, Barnyardgrass, Sprangletop (DNAs)
Palmer amaranth
Lambsquarters Sprangletop
Barnyardgrass
Kurt Hembree – March 11, 2015
http://www.weedscience.com
Kurt Hembree – March 11, 2015
How do you recognize herbicide
resistance in the field?
Kurt Hembree – March 11, 2015
If you have trouble controlling a specific
weed with a specific labeled herbicide a.i.
and/or are having to use higher and
higher rates of that a.i. to control a
particular weed, and you’ve ruled out any
errors associated with timing and
application, you may have resistance.
A Reality Check:
Some weeds can spread a long distance, so
resistant weeds may pop-up in your field by nothing
you’ve done, but it still has to be dealt with!
Kurt Hembree – March 11, 2015
Maybe it’s time to try
something different?
Kurt Hembree – March 11, 2015
Strategies for proactive
weed management:
“Keeping weeds susceptible”
“4-step program”
Kurt Hembree – March 11, 2015
Weed Seeds/plant
Horseweed/Marestail 1,000,000
Large crabgrass 150,000
Common lambsquarters 72,450
Common purslane 52,300
Barnyardgrass 40,000
Shepherd’s-purse 38,500
Prickly lettuce 27,900
Hairy fleabane 10,000
Yellow foxtail 6,420
Wild oats 250
1. Don’t add to the seed bank:
Kurt Hembree – March 11, 2015
Follow-up control of weed escapes,
including borders, edges, and ditches:
Kurt Hembree – March 11, 2015
2. Have a good spray operation:
► Sprayer performance
► Spray tip performance
► Rate(s) used
► Weather conditions
► Spray coverage issues
► Treatment timing
► Applicator skill and attitude
Kurt Hembree – March 11, 2015
3. Refer to the label for help:
Kurt Hembree – March 11, 2015
Kurt Hembree – March 11, 2015
4. Diversify the control tactics: Control tactic Potential impact
Herbicide – rotation (MOAs) Excellent
Herbicide – mixtures (MOAs) Excellent
Herbicide – timing Excellent
Herbicide – rate Fair
Herbicide – precision application Poor
Tillage – primary Good to Excellent
Tillage – general mechanical Fair to Good
Cultural – crop selection/rotation Fair to Good
Cultural – planting date Poor to Fair
Cultural – seeding rate Fair
Cultural – planting configuration Good
Cultural – cover crops, mulching Poor
Kurt Hembree – March 11, 2015
PRE + POST
POST
Kurt Hembree – March 11, 2015
Kurt Hembree – March 11, 2015
PRE + POST POST
0
10
20
30
40
50
9 14 10 22 3 4 5 2 1 7 12 8 21 15 17 29
Acre
s t
reate
d (
%)
WSSA MOA group number
Herbicide use in trees and vines in CA in 2010 (tree nuts, grapes, and stone fruits)
Source: CA DPR
glufosinate
paraquat
oxyfluorfen, flumioxazin,
carfentrazone, pyraflufen
glyphosate
80%
Kurt Hembree – March 11, 2015
0
10
20
30
40
50
9 7 14 3 1 2 15 5 10 17 met
Acre
age t
reate
d (
%)
WSSA MOA group number
Herbicide use in cotton in CA in 2011
Source: CA DPR
diuron
glyphosate
pendimethalin,
trifluralin
oxyfluorfen, flumioxazin
90%
Kurt Hembree – March 11, 2015
In almonds for example:
Preemergent
MOA
(group #)
Postemergent
MOA
(group #)
Matrix 2 Selectmax, Fusilade, Poast 1
Surflan, Prowl, Treflan 3 2,4-D 4
Princep 5 Roundup (others with glyphosate) 9
Eptam 8 Rely 280, Cheetah, Lifeline, etc. 10
Solicam 12 Shark, Goal, Venue, Chateau, Treevix 14
Chateau, Goal 14 MSMA 17
Trellis 21 Gramoxone Inteon 22
Alion 29
Pindar GT 2 + 14
Rotate and/or tank-mix
herbicides with different MOAs:
Kurt Hembree – March 11, 2015
Kurt Hembree – March 11, 2015
Untreated
Roundup (9)
Treevix (14) + Roundup (9)
Untreated Roundup (9) – 30 DAT
Roundup (9) + Chateau (14) – 30 DAT Rely 290 (10) + Chateau (14) – 30 DAT
Kurt Hembree – March 11, 2015
0
2
4
6
8
10
RU GR RL TV SK VU RU +VU
RU +TV
RU +CH
RU +SK
RL +SK
RL +RU
RL +VU
Contr
ol
Postemergence control of horseweed and hairy fleabane
Horseweed Fleabane
Kurt Hembree – March 11, 2015
Grape trial 2014 (90 DAT) Untreated Mission (2) + RU (9)
+ AMS + MSO
Mission (2) + Chateau (14) + RU (9)
+ AMS + MSO
Mission (2) + Alion (29) + RU (9)
+ AMS + MSO
Kurt Hembree – March 11, 2015
Glyphosate-resistant junglerice control:
T. Lanini, UC Davis
Kurt Hembree – March 11, 2015
http://ucipm.ucdavis.edu
Kurt Hembree – March 11, 2015
http://cefresno.ucdavis.edu
Kurt Hembree – March 11, 2015
US CA
Cotton – 90% Cotton – 85%
Corn – 80% Corn – 60%
Soybean – 80% Soybean – NA
Alfalfa – 5% Alfalfa – <10%
Kurt Hembree – March 11, 2015
Roundup Ready system concerns:
Weed shifts occur fairly quickly if we rely
on the same herbicide MOA year-after-year:
M. Canevari
Kurt Hembree – March 11, 2015
Pre-Roundup Ready Cotton…
• Weed control was based on:
– “yellow” herbicides PPI
– PRE herbicides at-planting
– POST-DIR at 3- to 4-inch cotton
– 3-4 Cultivations
– Non-selective herbicides under hoods
– Layby residual treatment
– Spot spraying
– Weeding by hoe crews
– Staple POST OTT in 1996
S. Wright
Kurt Hembree – March 11, 2015
Roundup Ready Cotton…
• Weed control is based on:
– “yellow” herbicides PPI or PRE ?
– Glyphosate OTT cotton (1-3X)
– Glyphosate POST-DIR (alone or with residuals)
S. Wright
Kurt Hembree – March 11, 2015
Vary the control tactics where practical:
Kurt Hembree – March 11, 2015
Make sure your treatment timing is
the same as the label’s timing:
Kurt Hembree – March 11, 2015
Horseweed control across postemergence herbicides tested
Parlier 2006
0
2
4
6
8
10
2-14 leaf Rosette 6-12" bolted
Horseweed growth stage
Co
ntr
ol
Kurt Hembree – March 11, 2015
Liberty Timing/Rate -- Palmer amaranth
0
10
20
30
40
50
60
70
80
90
100
2 4 6 8 10 12 unt.
Weed Height (inches)
We
ed
Co
ntr
ol (p
erc
en
t)
0.42 lb ai/A -- 7 DAT
0.42 lb ai/A -- 14 DAT
0.52 lb ai/A -- 7 DAT
0.52 lb ai/A -- 14 DAT
S. Wright and R. Vargas
Kurt Hembree – March 11, 2015
4TL, 1” or less >5 TL and >1”
Kurt Hembree – March 11, 2015
S. Wright and R. Vargas
Take-home points when considering
weed resistance management:
► Be proactive by keeping weeds susceptible, which includes
making changes to the program as needed.
► Have a strategy (“4-step program”)
1. Do what you can to prevent weeds from going to seed.
2. Make sure the spray operation is up to par.
3. Refer to the label for helpful guidelines.
4. Diversify efforts (MOAs, treatment timing, cultivation, etc.).
Kurt Hembree – March 11, 2015
“Improvise, Adapt, Overcome” Clint Eastwood – Heartbreak Ridge
Kurt Hembree – March 11, 2015