Transcript
Round
Ready
Right !
What are Herbicide Resistant Weeds?
What are Herbicide Resistant Weeds?
Weeds that aren’t controlled by a herbicide application…
What are Herbicide Resistant Weeds?
Weeds that aren’t controlled by a herbicide application… Ally just won’t get my … Roundup doesn’t control …
What are Herbicide Resistant Weeds?
Weeds that aren’t controlled by a herbicide application…
Herbicide tolerance and herbicide resistance are not the same thing
WSSA Herbicide Resistance Management Lesson 3 © 2011 WSSA All Rights Reserved
Herbicide Resistance Defined
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Herbicide resistance can be defined as the acquired ability of a weed population to survive a herbicide application that previously was known to control the population.
Herbicide tolerance is the inherent ability of a species to survive and reproduce after herbicide treatment. There has been no selection acting on the tolerant weed species, and there has been no change in the weed species lack of response to the herbicide over time.
Year 1 Year 2 Later years
The number of herbicide-resistant individuals in the population changes over time.
Year 1 Year 2 Later years
The number of herbicide-tolerant individuals is not affected directly by the herbicide.
WSSA Herbicide Resistance Management Lesson 3 © 2011 WSSA All Rights Reserved
Herbicide Resistance: Basic Principles
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Herbicide resistance is the result of naturally occurring processes.
* Biotypes are plants within a species that have biological characteristics that are not common to the population as a whole.
Herbicide-resistant individuals or biotypes* are present naturally within the weed population at very low frequencies. These individuals have a herbicide resistance mechanism that allows them to survive the application of a herbicide.
Weed control failures do not automatically mean that the weeds are herbicide-resistant.
Resistance is heritable. It can be passed from one
generation to the next.
In general, weed populations are genetically diverse, and individual plants within a species can respond differently to the same herbicide rate. This does not mean, in all cases, that the least sensitive individuals are herbicide-resistant, but it is a possibility. Herbicide rates are initially established to be effective on the vast majority of the individuals in a population under normal growing conditions. This is why using labeled rates is important.
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WSSA Herbicide Resistance Management Lesson 1 © 2011 WSSA All Rights Reserved WSSA Herbicide Resistance Management Lesson 1 © 2011 WSSA All Rights Reserved
Herbicide Mechanism of
Action
Number of Resistant Species
Herbicide Group
Number
ACCase-inhibitors (ex. Select herbicide)
40 1
ALS-inhibitors (ex. Classic herbicide)
108 2
Photosystem II-inhibitors (ex. atrazine)
68 5
Glycines (ex. glyphosate) 21 9
Current Status of Resistance
Source: www.weedscience.org,
Ian Heap, March 2011
The number of herbicide-resistant weed species is always increasing. For the most up-to-date information, please see the website below.
Mechanism of action (MOA) is the biochemical site within a plant with which a herbicide directly interacts. Herbicides with different MOAs are identified by different group numbers. For example, 2,4-D belongs to group 4 and glyphosate belongs to group 9. Herbicides are assigned into groups based on a WSSA approved system of categorizing based on mechanism of action.
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Herbicide Resistance in Southwest Oklahoma
• ALS resistant ryegrass? in other areas…may be creeping in
• Glyph resist. (GR) pigweeds –waterhemp, palmer amaranth? In adjacent regions, difficult in 2012
• GR horseweed - already in most counties
Untreated 0.25x 0.1875 lb ae
0.5x 0.375 lb ae
1x 0.75 lb ae
2x 1.5 lb ae
4x 3.0 lb ae
8x 6.0 lb ae
Susceptible Population
Photos taken 14 DAT. Treatments applied at 20 GPA with NIS at 0.25% v/v.
Rep 1
Rep 2
Rep 3
Rep 4
Untreated 0.25x 0.1875 lb ae
0.5x 0.375 lb ae
1x 0.75 lb ae
2x 1.5 lb ae
4x 3.0 lb ae
8x 6.0 lb ae
Resistant Population
Photos taken 14 DAT. Treatments applied at 20 GPA with NIS at 0.25% v/v.
Rep 1
Rep 2
Rep 3
Rep 4
Untreated 0.25x 0.1875 lb ae
0.5x 0.375 lb ae
1x 0.75 lb ae
2x 1.5 lb ae
4x 3.0 lb ae
8x 6.0 lb ae
Resistant Populations
Photos taken 14 DAT. Treatments applied at 20 GPA with NIS at 0.25% v/v.
Rep 1
Rep 2
Rep 3
Rep 4 Caddo
Tillman
Harmon
Jackson
How do we protect against resistance ?
How do we protect against resistance ?
• Incorporate herbicides with different modes of action (MOA).
How do we protect against resistance ?
• Incorporate herbicides with different modes of action (MOA); Tank-mix when possible
• Avoid using the same herbicide repeatedly
How do we protect against resistance ?
• Incorporate herbicides with different modes of action (MOA); Tank-mix when possible
• Avoid using the same herbicide repeatedly
• Always use the full labeled herbicide rate
How do we protect against resistance ?
• Incorporate herbicides with different modes of action (MOA); Tank-mix when possible
• Avoid using the same herbicide repeatedly
• Always use the full labeled herbicide rate
• Don’t forget fence rows/turn rows/ditches
How do we protect against resistance ?
• Incorporate herbicides with different modes of action (MOA); Tank-mix when possible
• Avoid using the same herbicide repeatedly
• Always use the full labeled herbicide rate
• Don’t forget fence rows/turn rows/ditches
• Be aware of what you might be bringing in… hay, seed, harvest equipment etc.
How do we protect against resistance ?
• Plan ahead….have any chemicals been hard to get lately?
• Make each application count… don’t trade speed for quality & choose rates acc. to weed size
• Diversify your practices… don’t rule out tillage or rotation
Water
Quality
Application
Speed
Environ
conditions
Application
Timing
Spray
Volume
Surfactants
Don’t Let Horseweed Get the Jump on Your Cotton . . . Start Clean and Stay Clean!
Horseweed Control
Suggestions In No-till Cotton
Use an effective control strategy …tank-mix with Glyphosate
Include 1.0 lb ai/acre - 2,4-D or 0.25 lb ai/acre - Dicamba
*
Remember labeled plant back intervals
-30 days after 2,4-D
-21 days after1” rainfall following Dicamba*
*Do not apply Dicamba in regions receiving less than 25” of average annual rainfall .
Spray when weeds are small
-Rosettes are easiest to
control
Pigweed Control Programs
for Oklahoma Cotton
On the Web
For More Info
Check the Web!
www.cotton.okstate.edu
or
www.weedscience.okstate.edu
No more bologna!
Do you get my drift ?
Horseweed (marestail, mulestail, $&#! etc.)
Palmer Amaranth
Glyphosate-Pigweed difficulties in 2012
Several in the
southwest ?
? ?
?
?
What’s at the end of your rainbow
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