2009 weed management in cotton. getting serious about herbicide-resistant weeds

20092009

Weed ManagementWeed Management

in Cottonin Cotton

Getting Serious AboutHerbicide-Resistant Weeds

Managing Herbicide Resistance

Attitudes and acceptance

• Resistance is real

• It can happen on any farm;

• It can happen with any herbicide; resistance is not unique to glyphosate

• Far better to prevent it, but learn to deal with it if you already have it

0 20 40 60 80 100 120

No. cases

ALS inhibitors

PS II inhibitors (triazines)

ACCase inhibitors

Glycines

DNA’s

Ureas

Auxins

Arsenicals

Bipyridiliums

Thiocarbamates

PPO inhibitors

Carotenoid biosyn. inhibitors

Nitriles

Herbicide Resistance in US by Mode of Action

ACY 2008

Glyphosate-Resistant Horseweed

Identified in 16 states Initially found in NC in 2003 Slow increase during 2003-2007; less than expected Exploded in eastern NC in 2008

Glyphosate-Resistant Horseweed

Resistant biotype likely will be more prevalent in 2009

Wind-borne seed; easily moves long distances

East of US 1, assume it is glyphosate-resistant and act accordingly;

implement appropriate burndown program Photo by R. Hayes

Burndown Programs for

Glyphosate-Resistant Horseweed in

Cotton, Corn, Full-season Soybean

First choice:

Roundup + Clarity (1/2 pt)* + residual herbicide

Time of horseweed emergence in west Tennessee. Adapted from Main et al., 2006.

0

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50

60

70

% o

f to

tal

Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug0

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30

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% o

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Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Jackson 2002-03 Milan 2002-03




First choice:


____________________________________________

* Waiting intervals required;

Apply mid-February to early March

Waiting Period after Clarity Preplant Application

Corn: no waiting period

Soybean: 14 days (for 8 oz rate)

Cotton: Following accumulation of 1 inch rainfall,

wait 21 days




First choice:


Second choice:

Roundup + 2,4-D (1.5-2 pt)* + residual herbicide____________________________________________

* Waiting intervals required;

Apply mid-February to early March

Waiting Period after 2,4-D Preplant Application*

Cotton

Crops listed as use sites on this or other registered 2,4-D labels may be planted within 29 days of application. All other crops (cotton included here) may be planted 30 or more days following application without concern for illegal residues in the planted crop. However, under certain conditions, there may be a risk of injury to susceptible crops. Degradation factors should be considered in weighing this risk. Less risk if conditions following application include warm, moist soils. Under normal conditions, any crop may be planted without risk of injury if at least 90 days of soil temperatures above freezing have elapsed since application.

* Includes some brands of both amine and ester formulations.

Edgecombe Co., NC 2008 8 weeks after burndown

Untreated Roundup only Roundup + Valor

Roundup + Valor + Clarity Roundup + Valor + 2,4-D

Roundup + Valor + Clarity Roundup + Valor + 2,4-D

Untreated Roundup only Roundup + Valor

Edgecombe Co., NC 2008 12 weeks after burndown (and after two in-crop applications Roundup,except check)




First and second choices:


Roundup + 2,4-D (1.5-2 pt)* + residual herbicide

Third choice:

Ignite (29 oz), temperature > 75F, at or near planting,

plus a residual

Fourth choice:

Gramoxone + PS II inhibitor (atrazine, Direx, Canopy, Linex)

(may not be adequate)____________________________________________

* Waiting intervals required

In-Crop Control of Glyphosate-Resistant Horseweed

Cotton: Ignite under hood (any variety)Ignite overtop LL variety

Ignite requires GOOD coverage

Ignite hooded on horseweed

(not LL cotton)

Oops!

Managing Glyphosate-Resistant Palmer Amaranth

Can’t ignore it and hope it goes away; it is not going away

• Prolific seed production

450,000 seed/plant grown in competition with

cotton (Sosnoskie and Culpepper, UGA)


Can’t ignore it and hope it goes away; it is not going away

• Prolific seed production

• Continued selection; can manage this

• Spread of resistance– Seed movement; equipment, gin trash– Pollen-mediated gene flow Pollen from resistant male can fertilize susceptible female at least 1,000 ft away;

resistant offspring (Sosnoskie and Culpepper, UGA)


Considerations in developing a management strategy

• Prevention is the goal; reduce seed bank



• Prevention is the goal; reduce seed bank

• No POST salvage options in cotton

What is the implication?



• Prevention is the goal


• ALS resistance (Staple, Envoke, others) is wide-spread; multiple resistance

Weathermax 88 oz

Staple LX 10 oz



• Prevention is the goal


• ALS resistance (Staple, Envoke, others) is wide-spread; multiple resistance

• Increasingly concerned over potential for resistance to PPO inhibitors

PPO inhibitors for the Southeast

Corn Cotton Peanut Soybean

Aim

Cadet

Resource

Valor

Cobra

Reflex

Valor

Blazer

Cobra

Valor

Aim

Authority/Sonic

Blazer

Cadet

Cobra

Envive

Flexstar

Prefix

Reflex

Resource

Valor

Valor XLT

Impacts of Roundup Ready TechnologyOn Cotton Weed Management

1. Reduced or eliminated use of other herbicides

2. Allowed successful transition to no-till

3. Eliminated cultivation

Impacts of Roundup Ready TechnologyOn Cotton Weed Management

1. Reduced or eliminated use of other herbicides

2. Allowed successful transition to no-till

3. Eliminated cultivation

4. Unprecedented selection pressure

for glyphosate-resistant biotypes

Herbicide Resistance Management

(avoidance)

The focus must be on

reducing selection pressure.

Glyphosate Resistance Management (reducing selection pressure)

1. Minimize the seed bank

2. Do not depend entirely on glyphosate

Incorporate other modes of action, specifically residuals, into the program; most effective to do that on the front end

3. Use full rates

4. Start clean, stay clean

5. Take advantage of non-chemical control where practical;

cultivation or cover crops

6. Vigilance! Watch for escapes, do not let them seed out

Is this weed resistant?Want to risk it?

ACY 2008

GR Palmer Amaranth Management in CottonSoutheast Recommendations

• Herbicide program:– Aggressive preplant/preemergence program.

Palmer amaranth control by PRE herbicides; 40 days*

0 20 40 60 80 100

Cotoran

Prowl

Direx

Caparol

Reflex

% control

* Average of 5 locations; 2 in GA, 3 in NC. Very heavy infestations. No other herbicides included.

Staple (susceptible)

PRE herbicides in Palmer amaranth management system. Four locations, NC.*

50 60 70 80 90 100

No PRE

Prowl

Direx

Reflex

Staple

Prowl + Reflex

Reflex + Direx

Reflex + Staple

Direx + Staple

* All with glyphosate/s-metolachlor POST-1, glyphosate POST-2, conventional layby.

Palmer amaranth control by PRE herbicides; 40 days*

0 20 40 60 80 100

Cotoran

Prowl

Valor

Direx

Caparol

Reflex

Staple (susceptible)

% control

* Average of 5 locations; 2 in GA, 3 in NC. No other herbicides included.

Strip-Till After Valor Preplant

Waiting Intervals for Valor Preplant in Cotton

2 oz/acre

14 daysStrip-till, with tillage operation between Valor application and planting

21 days and

accumulation of

1 inch rainfall

No-till, with residue

30 days and

accumulation of

1 inch rainfall

Stale beds, no cover

GR Palmer Amaranth ManagementSoutheast Recommendations

• Herbicide program:– Aggressive preplant/preemergence program.

– Dual Magnum (or other metolachlor product)

early POST; to extend residual control

– Residual herbicide(s) lay-by

– Limit PPO inhibitors to one application/year

Roundup + 2,4-D burndownGram. + Reflex PRERoundup + Dual first POSTRoundup second POSTDirex + MSMA Layby

Glyphosate-resistant Palmer amaranth, Wayne Co., NC 2008;

PRE herbicide followed by Roundup tank mix

Most POST soybean herbicide labels

specify 6-leaf or 4-inch maximum

Palmer amaranth

Harmony SG label specifies 8-inch

maximum Palmer amaranth

ACY 2008

Untreated Atrazine-based program

Herbicide Resistanceand Crop Insurance

• Concern by insurance companies

• Failure to follow good farming practices

is not an insurable loss

• Keep records to document what you did,

and whose advice you followed

Get Serious About

Herbicide-Resistant Weeds

2009 weed management in cotton. getting serious about herbicide-resistant weeds

Documents

cotton slide

days slide

d slide

glyphosate resistant

uga slide

residual herbicide slide

hayes slide

check slide