Conyza bonariensis
glyphosate-resistant:
the need for a new approach.
Miguel-Angel Sevillano, Juan Trigo, Gabriel Pardo, Jose-Maria Urbano
1
Huesca, September 6th, 2011
Introduction

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))
2
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Introduction

Conyza bonariensis
• Over-reliance on glyphosate
increases the problem.
3
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Introduction

Conyza bonariensis
• Farmers want to have bare soil
• At least in the line of trees
• With glyphosate mixtures
• Which mixtures?
4
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Introduction

MOA that have been proposed to control C. bonariensis
• Flazasulfuron (B)
• Terbutilazine (C1)
• Amitrol (F3)
• Glyphosate (G)
• Glufosinate (H)
• Fluroxipyr (O)
• MCPA (O)
5
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Introduction

Since 2004, glyphosate + flazasulfuron is recommended
Localidad 19 (resistente).
T4: Glyphosate (1080 g/ha)
+ Flazasulfuron (50 g/ha)
6
T2: Glyphosate (1080 g/ha)
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Introduction
In 2009, control failures are reported in Ecija (Sevilla), after
glyphosate + flazasulfuron, in olive farms.

7
Conyza bonariensis glyphosate-resistant: the need for a new approach.
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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Conyza bonariensis glyphosate-resistant: the need for a new approach.
Material and Methods

5 C. bonariensis pops.
- A: susceptible check (2004)
- B, C, D: Ecija’s pops (2009)
- E: glyphosate resistant check (2004)

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5 pops x 10 treatments x 6 reps x 2 (twice)
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Material and Methods

10
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
6
Amitrol
Glyphosate + Amitrol
3
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
Conyza
bonariensis glyphosate-resistant: the
need+for
a new approach.
Material and Methods

Data
•Chlorophyll
•Fitotoxicity
•Mortality
•Biomass
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Conyza bonariensis glyphosate-resistant: the need for a new approach.
Material and Methods

Dates
Sowing
Emergence
Trasplanting
1st evaluation
Spraying
2nd evaluation
3rd evaluation
4th evaluation
5th evaluation
Biomass
Date
05/10/2010
11/10/2010
25/10/2010
15/11/2010
15/11/2010
22/11/2010
29/11/2010
06/12/2010
13/12/2010
16/12/2010
Trial 1
DDS*
0
6
20
41
41
48
55
62
69
72
DDT**
0
7
14
21
28
31
Date
14/10/2010
20/10/2010
05/11/2010
22/11/2010
22/11/2010
29/11/2010
06/12/2010
13/12/2010
20/12/2010
20/12/2010
Trial 2
DDS*
0
6
22
39
39
46
53
60
67
67
DDT**
0
7
14
21
28
28
*DDS: Days after sowing.
**DDT: Days after trasplanting.
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Conyza bonariensis glyphosate-resistant: the need for a new approach.
Results
Glyphosate
12
GLI 28DDT
Fitotoxicidad
a
10
a
b
b
0
2
4
6
8
b
A
B
C
D
E
B & D pops: glyphosate resistant
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Conyza bonariensis glyphosate-resistant: the need for a new approach.
Results
Glyphosate
Mortalidad 28DDT
a
1.0
GLI
0.4
0.6
0.8
a
b
0.2
b
0.0
b
A
B
C
D
E
Resistant pops survive
14
Conyza bonariensis glyphosate-resistant: the need for a new approach.
Results
Flazasulfuron
FLAZA
10
12
1.0
FLAZA
Mortalidad 28DDT
a
a
0.4
6
0.6
8
0.8
Fitotoxicidad 28DDT
4
ab
b
2
0.2
0
0.0
b
A


15
B
C
D
E
a
a
a
a
a
A
B
C
D
E
Lack of eficacy, when applied in postemergence.
There is diferential response, but not resistance.
Results
Glyphosate + flazasulfuron
Mortalidad 28DDT
1.0
GLI+FLAZA
0.6
0.8
a
0.4
ab
bc
0.2
bc
0.0
c
A

16
B
C
D
E
Lack of eficacy against resistant pops
Results
MCPA & Fluroxypir
Mortalidad 28DDT
FLURO
MCPA
Testigo
0.8
10
12
1.0
Fitotoxicidad 28DDT
a
a
a
a
4
0.4
6
0.6
8
a
2
0.2
a
a
a


17
a
0.0
0
A

a
B
C
D
E
A
B
C
Similar results: relatively good eficacy
No diferential response
Mortality is low
D
E
Results
Glyphosate + auxinics
GLI+DICA 28DDT
Fitotoxicidad
Mortalidad
GLI+DICA 28DDT
12
1.0
a
a
a
a
ab
8
b
0.8
10
ab
0.6
a
a
0
0.0
2
0.2
4
0.4
6
a
A


18
B
C
D
E
Increased eficacy
Mortality is not 100%
A
B
C
D
E
Results
AMI
AMI
1.0
12
Amitrol
Fitotoxicidad 28DDT
a
a
Mortalidad 28DDT
0.8
10
a
b
b
0.6
8
b
0
A


19
b
b
b
C
D
E
0.0
2
0.2
4
0.4
6
ab
B
C
D
E
A
Phytotoxic
Low mortality in problematic pops
B
Results
Glyphosate + amitrol
GLI+AMI
GLI+AMI
10
a
1.0
a
Mortalidad 28DDT
ab
0.8
12
Fitotoxicidad 28DDT
abc
ab
c
0.4
6
0.6
8
bc


20
b
D
E
0.0
2
0
A

b
0.2
4
b
B
C
D
E
Glyphosate + amitrol = amitrol
Low mortality
Not very interesting
A
B
C
Conclusions


None of the treatments achieved 100% control
What should we do know?
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
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