conyza bonariensis glyphosate-resistant: the need for a new approach

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Conyza bonariensis glyphosate-resistant:

the need for a new approach.

Huesca, September 6th, 2011

Miguel-Angel Sevillano, Juan Trigo, Gabriel Pardo, Jose-Maria Urbano

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Introduction

Conyza bonariensis glyphosate-resistant: the need for a new approach.

Conyza bonariensis

• Major weed problem in no-till permanent crops in Spain

• Adapted to develop herbicide resistance:

- Worldwide (B, C1, D, G)

- In Spain (C1 (1987), G (2004))

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Introduction


Conyza bonariensis

• Over-reliance on glyphosate increases the problem.

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Introduction


Conyza bonariensis

• Farmers want to have bare soil

• At least in the line of trees

• With glyphosate mixtures

• Which mixtures?

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Introduction


MOA that have been proposed to control C. bonariensis

• Flazasulfuron (B)

• Terbutilazine (C1)

• Amitrol (F3)

• Glyphosate (G)

• Glufosinate (H)

• Fluroxipyr (O)

• MCPA (O)

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Introduction


Since 2004, glyphosate + flazasulfuron is recommended

T2: Glyphosate (1080 g/ha)T4: Glyphosate (1080 g/ha)+ Flazasulfuron (50 g/ha)

Localidad 19 (resistente).

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Introduction


In 2009, control failures are reported in Ecija (Sevilla), after glyphosate + flazasulfuron, in olive farms.

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Objectives


Confirm glyphosate resistance in Ecija pops

Check for flazasulfuron resistance in Ecija pops

Evaluate the eficacy of:

- Amitrol (F3)

- MCPA (O)

- Fluroxipyr (O)

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Material and Methods


5 C. bonariensis pops.

- A: susceptible check (2004)

- B, C, D: Ecija’s pops (2009)

- E: glyphosate resistant check (2004)

5 pops x 10 treatments x 6 reps x 2 (twice)

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10 treatments:

Treatment Active ingredient Rate (kg ai/ha)

1 Check -

2 Glyphosate 1,08

3 Flazasulfuron 0,0375

4 Glyphosate + Flazasulfuron 1,08 + 0,0375

5 Amitrol 3

6 Glyphosate + Amitrol 1,08 + 3

7 Fluroxipir 0,3

8 Glyphosate + Fluroxipir 1,08 + 0,3

9 MCPA 1,08

10 Glyphosate + MCPA 1,08 + 1,08

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Data

•Chlorophyll

•Fitotoxicity

•Mortality

•Biomass

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Dates

Trial 1 Trial 2 Date DDS* DDT** Date DDS* DDT**

Sowing 05/10/2010 0 - 14/10/2010 0 -

Emergence 11/10/2010 6 - 20/10/2010 6 -

Trasplanting 25/10/2010 20 - 05/11/2010 22 -

1st evaluation 15/11/2010 41 - 22/11/2010 39 -

Spraying 15/11/2010 41 0 22/11/2010 39 0

2nd evaluation 22/11/2010 48 7 29/11/2010 46 7

3rd evaluation 29/11/2010 55 14 06/12/2010 53 14

4th evaluation 06/12/2010 62 21 13/12/2010 60 21

5th evaluation 13/12/2010 69 28 20/12/2010 67 28

Biomass 16/12/2010 72 31 20/12/2010 67 28

*DDS: Days after sowing.

**DDT: Days after trasplanting.

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A B C D E

GLI

02

46

81

01

2

a

b

a

b b

Results


Glyphosate

B & D pops: glyphosate resistant

Fitotoxicidad 28DDT

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A B C D E

GLI

0.0

0.2

0.4

0.6

0.8

1.0

a

b

a

b

b

Glyphosate

Resistant pops survive

Mortalidad 28DDT

Results


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A B C D E

FLAZA

02

46

81

01

2

a

bab

b

a

Flazasulfuron

Lack of eficacy, when applied in postemergence. There is diferential response, but not resistance.

A B C D E

FLAZA

0.0

0.2

0.4

0.6

0.8

1.0

a a a a a

Fitotoxicidad 28DDT Mortalidad 28DDT

Results

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Glyphosate + flazasulfuron

Lack of eficacy against resistant pops

A B C D E

GLI+FLAZA

0.0

0.2

0.4

0.6

0.8

1.0

a

c

ab

bc

bc

Mortalidad 28DDT

Results

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MCPA & Fluroxypir

Similar results: relatively good eficacy No diferential response Mortality is low

A B C D E

FLURO

02

46

81

01

2

aa a

a a

Fitotoxicidad 28DDT Testigo Mortalidad 28DDT

A B C D E

MCPA

0.0

0.2

0.4

0.6

0.8

1.0

a

a a

a

a

Results

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Glyphosate + auxinics

Increased eficacy Mortality is not 100%

A B C D E

GLI+DICA

02

46

81

01

2

a

aba

ab

b

A B C D E

GLI+DICA

0.0

0.2

0.4

0.6

0.8

1.0

a

a

a

aa


Results

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A B C D E

AMI

02

46

81

01

2

aa

b b b

Amitrol

Phytotoxic Low mortality in problematic pops

A B C D E

AMI

0.0

0.2

0.4

0.6

0.8

1.0

a

ab

b b b


Results

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A B C D E

GLI+AMI

02

46

81

01

2

a

abc

ab

bc c

Glyphosate + amitrol

Glyphosate + amitrol = amitrol Low mortality Not very interesting

A B C D E

GLI+AMI

0.0

0.2

0.4

0.6

0.8

1.0 a

b

ab

b b


Results

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None of the treatments achieved 100% control What should we do know?

Conclusions

Estrategy A:- Increase herbicide rates- Add other products to the mixture

Estrategy B:- Are we optimizing the moment ?- Are we optimizing cultural practices (cover crops) ?- Have we explored all posibilities of non-chemical control

(mechanical, physical, biological) ?- Can we predict the emergence ?

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Thanks for your attention

conyza bonariensis glyphosate-resistant: the need for a new approach

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