Grains Research and Development

Date: 22.02.2012

Sorting out problem weeds - Flaxleaf fleabane

Figure 1. Fleabane field emergence at the Research Station of Wagga Wagga Agricultural Institute (2011).

Sorting out problem weeds – Flaxleaf fleabane

Hanwen Wu and E. Koetz
EH Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University)

Introduction

Flaxleaf fleabane (C. bonariensis) is native to South America. Its introduction into Australia can be traced back to 1840s. It has recently emerged as a difficult-to-control weed in the south eastern states of Australia. It was first identified as a major crop weed in northern New South Wales and southern Queensland, but it has now widely spread into southern states. It severely infests cropping areas, roadsides and other non-agricultural lands. A number of factors have contributed to its rapid spread, including reduced cultivation as a result of wide adoption of no-till farming systems, reduced use of effective pre-emergence herbicides, ineffective post-emergent herbicides as well as the unique biological characteristics of this weed.

Currently, industry research has been concentrated on improved herbicide control efficacy in cereal crops and fallows in the northern grain region. Little information is available on effective herbicide control on fleabane especially in degraded lucerne pastures in the southern region. Recently, many pasture paddocks have been seen heavily infested with fleabane. Although fleabane plants can be grazed by sheep, its re-growth characteristic makes the grazing option ineffective. This article addresses the biology of fleabane and its impact on effective management.

Emergence


On-farm field emergence was monitored at the Research Station of Wagga Wagga Agricultural Institute in 2011. The data showed that fleabane predominantly emerged in winter and early spring (97%), with limited emergence in summer and in the dry autumn period. This unique emergence pattern in southern NSW is in contrast to a similar study conducted in southern Queensland, where fleabane emerged in as early as May and the majority of emergence fleabane occurred in autumn, early and late winter (99%). Warm summer conditions discourage fleabane emergence, as fleabane prefers cool temperature for germination. The optimum germination temperature for fleabane is around 20-25 °C. It can not germinate below 5°C or above 35°C.

The predominant emergence of fleabane in southern NSW suggests that control efforts should focus on these major cohorts in winter and spring. Don’t leave it until summer when weeds mature and are often under moisture stress. Controlling weeds in the summer is often less effective due to the less ideal spraying conditions.

Figure 1. Fleabane field emergence at the Research Station of Wagga Wagga Agricultural Institute (2011).

Fleabane control in winter fallows

A winter fallow trial on fleabane was conducted in southern NSW in 2011. A high infestation of fleabane seedlings (>3,500 plants/m2) was evenly distributed across the paddock under a heavy stubble. Stubble was burnt on 16 September 2011 and the trial was sprayed with eight selected treatments on 21 September 2011.

The most effective treatments were glyphosate mixing with Tordon® 75D with and without the follow-up application of Spray.Seed®, both achieving > 90% control at 57 and 78 days after treatment (DAT) (Table 1). The three-way mix of glyphosate + 2, 4-D + atrazine also gave 95% control on fleabane when assessed at 78 and 110 days DAT. This three-way mix was the only treatment showing excellent long-term residual control of fleabane even after 110 days of herbicide application.

However, the majority of the treatment did not achieve satisfactory control (< 90%), including the commonly used glyphosate mixing with 2,4-D and the Spray.Seed treatments. Even the double knock treatment of glyphosate mixing with 2, 4-D followed by 7 days later with Spray.Seed only achieved 74-80% control.


Table 1. Herbicide control on fleabane in winter fallows (Wagga Wagga, 2011)

Treatment
Rate
Weed density
Visual rating (%)
 
 
57 DAT
78 DAT
110 DAT
Untreated
 
115
158
0
Glyphosate CT + Surpass® 475
1.5L + 1.0L
62 (46)
68 (57)
50
(Glyphosate CT + Surpass 475) à Spray.Seed
1.5L + 1.0L à 2.0L
30 (74)
31 (80)
50
(Glyphosate CT + Surpass 475) à   Alliance®
1.5L+ 1.0L à 2.0L
61 (47)
35 (78)
50
Glyphosate CT + Surpass 475 + Atrazine
1.5L+ 1.0L + 4L
22 (81)
7 (95)
95
Glyphosate CT + Tordon 75D
1.5L + 0.7L
5 (95)
10 (94)
85
(Glyphosate CT + Tordon 75D) à Sprayseed
1.5L + 0.7L à 2.0L
1 (99)
4 (97)
90
Spray.Seed
2.0L
40 (66)
69 (56)
0
LSD0.05
19.07
33.59
12.22

 

 

 

 

 

 

 

 

 

 

 

Data in the parenthesis are the % control (100 – control/treated*100). Treatments were applied to fleabane seedlings < 8cm across on 21 September 2011.

Fleabane control in lucerne pasture

A degraded pasture field site near Junee, southern NSW, was selected due to the high levels of mature fleabane in the summer of 2010/2011. Thirty five herbicide treatments were applied on 1 July 2011. Fleabane visual rating was assessed over time.

Most treatments did not achieve commercially acceptable control (Table 2). Gramoxone® (1.6L/ha) mixing with atrazine (1.5kg/ha), diuron (1.5kg/ha) or simazine (1.5kg/ha) were the only three treatments showing excellent residual control. These mixtures gave better control on fleabane when compared to the stand alone treatment of atrazine, diuron or simazine. However, only Gramoxone (1.6L/ha) mixing with atrazine (1.5kg/ha) continued to show excellent residual activity, achieving 93% control of fleabane at 164 days after treatment (about 5.5 months).

Table 2. Herbicide control efficacy on fleabane (visual rating, % control).

Treatment
Group
23-Aug
13-Oct
13-Dec
53 DAT
104 DAT
164 DAT
Cut 1
Cut 2
Untreated
 
0
0
0
73
83
25g Broadstrike + 0.5% Uptake® Spraying Oil
B
37.3
23.3
70
72
85
50g Broadstrike + 0.5% Uptake
B
47.3
36.7
63
88
90
25g Broadstrike + 1kg simazine 900DF + 0.5% Uptake
B + C
85
70
73
92
90
25g Broadstrike + 1.5L Buttress + 0.2% Chemwet® 1000
B + I
70
33.3
75
85
87
25g Broadstrike + 500g Diuron 900 DF + 0.2% Chemwet 1000
B + C
50
20
47
80
75
25g Broadstrike + 1.5L Bromoxynil + 0.5% Uptake
B + C
45
33.3
70
92
80
200ml Gramoxone 250 + 1kg Simazine 900DF + 500ml Jaguar®
L + C
75
76.7
52
90
88
2L Bromoxynil
C
45
20
37
83
90
500ml Velocity + 1% Hasten®
H
15
13.3
33
75
83
300ml Starane Advanced + 0.5% Uptake
I
10
10
17
73
72
50g Raptor® + 0.5% Uptake+ 2% Liase
B
60
0
47
75
63
100g Spinnaker® 700WDG + 0.5% uptake
B
5
13.3
37
73
67
1L Jaguar
C
30
16.7
60
80
70
2.5L Buttress + 2% Liase®
I
68
36.7
40
77
68
1.6L Gramoxone 250 + 1kg Simazine 900 DF
L + C
95
98.3
75
93
78
400ml Ecopar® + 2L Buttress
G + I
50
13.3
33
87
60
400ml Ecopar + 500ml Igran® 500F
G + C
15
0
0
68
63
400ml Ecopar + 1kg Terbyne® 750WG
G + C
15
0
3
82
77
1.5L Alliance
L + Q
50
0
47
80
83
2.8L Amitrole
Q
3.3
0
7
68
33
100g Gallery® 75DF + 0.5% Uptake
O
0
0
13
82
83
1kg Terbyne  750WG
C
25
0
40
82
70
1kg Prometryn® 900DF 
C
15
0
13
83
62
100g Balance
H
72.7
43.3
43
87
68
2.5L Boxer® Gold
K + J
7.3
0
40
83
82
118g Sakura®
K
3.3
0
10
87
83
1.5kg Simazine 900DF
C
90
73.3
55
87
83
1.5kg Atrazine 900DF + 0.5% uptake
C
89
73.3
45
90
83
1.5kg Diuron 900DF
C
58.3
13.3
22
80
68
750ml Outlook®
K
40
0
53
85
87
 3L Stomp® Xtra
D
3.3
0
17
80
75
1.6L Gramoxone 250 + 1.5kg Diuron 900DF
L + C
95
86.7
62
83
80
1.6L Gramoxone 250 + 1.5kg Atrazine
L + C
95
100
93
96
96
20g Lontrel 750 SG + 500mL MCPA amine
I + I
15
23.3
73
88
90
 LSD0.05
16.99
8.67
37.70 
 17.44
23.09 

On 13 October 2011, each plot was divided into three subplots, with both ends of the plot cut and raked to mimic grazing or forage cut. On 4 November, one cut-end was treated with simazine (1.5kg/ha) + Gramoxone (1L/ha), designated as Cut1  single knock. The other cut-end was treated with Broadstrike® (50g/ha) + Buttress® (2L/ha) on 27 October and was followed by 7 days later simazine (1.5kg/ha) + Gramoxone (1L/ha) on 4 November, designated as Cut2  double knock. The middle uncut area was used as a control to continue monitoring the herbicide efficacy applied on 1 July 2011. Results showed that both October treatments of Cut followed by either single knock or double knock significantly improved fleabane control. It is critical to apply herbicides after grazing or forage cut, otherwise fleabane can regrow quickly and respond with many more aggressive stems. It was also noted that fleabane flourished in the bare areas. Herbicides seem to be more effective on fleabane in the presence of lucerne competition.

On the other hand, many herbicide treatments caused significant damages to the pasture species (Table 3). There were four treatments causing damages to lucerne by more than 40%, including Amitrole®, Alliance, Balance® and the mix of Lontrel® 750 SG and MCPA amine. Subclover and chicory were more sensitive to the herbicide treatments than lucerne. Subclover was highly sensitive to those treatments containing atrazine, diuron, simazine, Amitrole, Alliance, Velocity® or Starane® Advanced.

The three effective treatments on fleabane control, i.e. Gramoxone (1.6L/ha) mixing with atrazine (1.5kg/ha), diuron (1.5kg/ha) or simazine (1.5kg/ha), caused limited damage to lucerne, but they had huge impact on subclover and chicory.

Table 3. Herbicide injury on pasture species 28 DAT (visual rating, % control).
 
 
 
 
 
Treatment (rate/ha)
Group
 Lucerne
Subclover
Chicory
Untreated
 
0
0
0
25g Broadstrike + 0.5% Uptake Spraying Oil
B
0
0
0
50g Broadstrike + 0.5% Uptake
B
0
0
0
25g Broadstrike + 1kg simazine 900DF + 0.5% Uptake
B + C
0
0
0
25g Broadstrike + 1.5L Buttress + 0.2% Chemwet 1000
B + I
0
0
43.3
25g Broadstrike + 500g Diuron 900 DF + 0.2% Chemwet 1000
B + C
0
53.3
33.3
25g Broadstrike + 1.5L Bromoxynil + 0.5% Uptake
B + C
0
0
30
200ml Gramoxone 250 + 1kg Simazine 900DF + 500ml Jaguar
L + C
10
46.7
46.7
2L Bromoxynil
C
0
0
30
500ml Velocity + 1% Hasten
H
36.7
70
46.7
300ml Starane + 0.5% Uptake
I
13.3
83.3
43.3
50g Raptor + 0.5% Uptake+ 2% Liase
B
0
0
30
100g Spinnaker 700WDG + 0.5% uptake
B
6.7
13.3
26.7
1L Jaguar
C
16.7
16.7
36.7
2.5L Buttress + 2% Liase
I
3.3
0
33.3
1.6L Gramoxone 250 + 1kg Simazine 900 DF
L + C
20
73.3
70
400ml Ecopar + 2L Buttress
G + I
10
26.7
30
400ml Ecopar + 500ml Igran 500F
G + C
10
23.3
20
400ml Ecopar + 1kg Terbyne 750WG
G + C
10
20
13.3
1.5L Alliance
L + Q
56.7
76.7
70
2.8L Amitrole
Q
76.7
83.3
73.3
100g Gallery 75DF + 0.5% Uptake
O
0
3.3
3.3
1kg Terbyne  750WG
C
0
0
0
1kg Prometryn 900DF 
C
0
0
0
100g Balance
H
43.3
36.7
70
2.5L Boxer Gold
K + J
0
26.7
13.3
118g Sakura
K
0
0
0
1.5kg Simazine 900DF
C
0
50
16.7
1.5kg Atrazine 900DF + 0.5% uptake
C
6.7
96.7
20
1.5kg Diuron 900DF
C
0
96.7
26.7
750ml Outlook
K
0
16.7
13.3
 3L Stomp Xtra
D
0
0
0
1.6L Gramoxone 250 + 1.5kg Diuron 900DF
L + C
23.3
88.3
46.7
1.6L Gramoxone 250 + 1.5kg Atrazine
L + C
20
93.3
63.3
20g Lontrel 750 SG+ 500mL MCPA amine
I + I
70
16.7
66.7
 LSD0.05
7.44
10.94
13.31

Conclusion

Herbicide control efficacy depends highly on the timing of application (weed growth stage and times of the year and the day), the use of herbicide mixtures, sequential application as well as the strategic use of residual herbicides. Limited herbicide options are available for fleabane control in lucerne based pastures. It is important to control fleabane after grazing, otherwise the fleabane will flourish as a result of little competition. A system approach, targeting crops, pastures, fallows, fenceline and roadside, is needed to effectively manage the fleabane. Any missing link will mean control failure, as the air-borne seeds of this weed will cause re-infestation and infestation to new areas.

Acknowledgement


This research was funded by the Grains Research & Development corporations. The authors acknowledge technical assistance for the pasture trial from Mr Colin Plater of Dow AgroSciences and Mr Neil Durning of AGnVET Services

Contact details

Dr Hanwen Wu
Wagga Wagga Agricultural Institute, NSW Department of Primary Industries, PMB, Wagga Wagga NSW 2650, Australia.
hanwen.wu@dpi.nsw.gov.au  
02 69381602

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