Blank slide template - — No-Till

Round

Ready

Right !

What are Herbicide Resistant Weeds?


Weeds that aren’t controlled by a herbicide application…


Weeds that aren’t controlled by a herbicide application… Ally just won’t get my … Roundup doesn’t control …


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

9

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

10

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.

[Click to close.]

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.

[Click to close.]

11

http://www.weedscience.org/

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


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


Rep 1

Rep 2

Rep 3

Rep 4


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


Rep 1

Rep 2

Rep 3

Rep 4 Caddo

Tillman

Harmon

Jackson

How do we protect against resistance ?


• Incorporate herbicides with different modes of action (MOA).


• 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





• Don’t forget fence rows/turn rows/ditches

• Be aware of what you might be bringing in… hay, seed, harvest equipment etc.


• 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

Documents

Blank slide template - — No-Till