Controlling annual ryegrass in fencelines/fallows and reducing glyphosate resistance development 2014 trial report

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Two control timings were investigated to control weeds in fencelines, once early in the year with a good residual and a knockdown, followed by another one later in the season (after the seeding and post-harvest operations are over). This enables managing fenceline weeds early in the season then killling them off later, rather than having to spray big fat weeds in one pass.

Background

Annual ryegrass is a major weed across Western Australia and the number of glyphosate resistant populations is increasing.

Across Australia 25% of documented ryegrass populations with glyphosate resistance have been found in fencelines.

Weeds that grow on fence lines can move into cropping fields taking their resistance status with them and so their management is imperative.

In 2012, the Grains Research and Development Corporation (GRDC) funded Northern and Esperance Advisor Groups explored 13 alternatives to glyphosate in two fenceline trials to prevent the onset of resistance in annual ryegrass.

One of these trials was at the Esperance Downs Research Station field day.

In 2012, tank mixes of residual herbicides plus either paraquat or Alliance gave the best control.

These trials had a single spray application in August.

In 2013, two earlier (but single) application times (May and June) of a range of herbicides were explored for fencelines.

Although some of those treatments gave 98% control, none of them offered complete control.

In 2014, both groups decided that two control timings were needed, once early in the year with a good residual and a knockdown, followed by another one later in the season (after the seeding and post-harvest operations are over).

This way you set up the fencelines early in the season then kill them off later rather than having to spray big fat weeds in in one pass.

Aim

The aim of this work is to explore herbicide and application timing alternatives to control annual ryegrass and other weeds in fencelines and prevent the onset of resistance.

Trial details

Table 1 Trial details, Buntine trial

Property

Ross, Lyn and Shaun Fitzsimons (Liebe Group main field day site)

Soil type

Sand

Treatments

Refer to Table 3 for details

(T1=27 May 2014, T2=3 July 2014, T3=6 August 2014, T4=20 August 2014)

Replicates

Three

 

Table 2 Trial details, West Binnu trial

Property

Scott Bridgeman

Soil type

Red loam

Treatments

Refer to Table 3 for details

(T1=26 May 2014, T2=18 June 2014, T3=27 July 2014, T4=6 and 8 August 2014)

Replicates

Three

 

Table 3 Treatment details, Buntine and West Binnu trials

Treatment number

First application

Timing

Second application

Timing

1

Simazine granules 4kg/ha + Alliance® 4L/ha

T1

Atrazine granules 2.2kg/ha + paraquat 250 3.6L/ha

T4

2

Simazine granules 4kg/ha + Alliance® 4L/ha

T1

Cultivate

T4

3

Simazine granules 4kg/ha + Alliance® 4L/ha

T1

Nil

T4

4

Simazine granules 4kg/ha + 2,4-D 700mL/ha + paraquat 250 3.6L/ha

T1

Atrazine granules 2.2kg/ha + paraquat 250 3.6L/ha

T4

5

Simazine granules 4kg/ha + 2,4-D 700mL/ha + paraquat 250 3.6L/ha

T1

Cultivate

T4

6

Simazine granules 4kg/ha + 2,4-D 700mL/ha + paraquat 250 3.6L/ha

T1

Nil

T4

7

Bromacil (Uragan®) 3.5kg/ha + paraquat 250 3.6L/ha

T1

Nil

T4

8

Bromacil (Uragan®) 5kg/ha + paraquat 250 3.6L/ha

T1

Nil

Nil

9

Oxyflurofen (Cavalier®) 4L/ha + paraquat 250 3.6L/ha

T1

Atrazine granules 2.2kg/ha + paraquat 250 3.6L/ha

T4

10

Slash

T3

Atrazine granules 2.2kg/ha + paraquat 250 3.6L/ha

T4

11

Simazine granules 4kg/ha + 2,4-D 700mL/ha + paraquat 250 3.6L/ha (July timing)

T2

Nil

Nil

12

Cultivate

T2

Atrazine granules 2.2kg/ha + paraquat 250 3.6L/ha

T4

13

Control

Nil

Nil

Nil

Results

Early results from six herbicide trials across the WA wheatbelt show:

  • A two spray or double knock strategy is often required for complete control in fencelines with the first application early in the season (most trials were sprayed in May).
  • The simazine plus Alliance® and simazine, 2,4-D and paraquat treatments in the first application gave reasonable control over all sites. The residual activity of the simazine ran out mid-season and there were a few ryegrass plants emerging in August.
  • The addition of Alliance® gives good broadleaf control (three year results).
  • The amount of stubble at spraying affected the efficacy of the first application. At those sites with very little stubble at spraying (Doodlakine and Buntine), all early applications (residual herbicides plus paraquat) gave good control. The trial at Northampton (heavier soil and more stubble) had very good control with bromacil and oxyflurofen (with paraquat) but the treatments with simazine and Alliance and simazine, 2,4-D and paraquat had some older annual ryegrass plants in the plots (all broadleaf weeds controlled). These plots needed the second application.
  • Bromacil showed 100% control at all sites after the first spray application. Bromacil can kill non-target vegetation at higher rates so it not for use in all circumstances. Lower rates will be investigated in the future.
  • Oxyflurofen is not registered for fencelines at these rates.
  • A later spray in June failed to give complete control mainly due to the size of the weeds.

Contact information

Author

Sally Peltzer