Rotate to reduce resistance

GroundCover Live and online, stay up to date with daily grains industry news online, click here to read more

Rotating crops and herbicides slows ALS herbicide resistance development in wild radish

PHOTO: Andrew Storrie, Agronomo

Growers in the southern cropping region can learn from the experience of their western counterparts to slow the development of herbicide-resistant wild radish, which has developed widespread multiple resistance to herbicides in Western Australia
 

Rotating crops and herbicides with diverse modes of action can slow the build-up of wild radish with resistance to acetolactate synthase (ALS) herbicides (Group B herbicides), according to GRDC-funded Department of Agriculture and Food, Western Australia (DAFWA) research.

In a four-year field trial at Beverley in the central WA wheatbelt, researchers compared the impact of a conventional and alternative crop rotation treated with either a high or low frequency of ALS applications on the resistance dynamics of a ryegrass population with an initially low level of resistance to ALS inhibitors (Table 1).

The number of wild radish plants with ALS resistance increased exponentially following repeated application of ALS herbicides in a continuous wheat-lupin rotation over four years (Figure 1).

Introducing TT canola into the wheat-lupin rotation and applying auxinic herbicides in the wheat crop and triazines in canola resulted in complete radish control and no build-up of ALS-resistance over the four-year trial.

Competition from the resistant wild radish in the conventional rotation reduced wheat and lupin yields by about two-thirds of those in the TT-canola rotation.

   Year 1
 Year 2
 Year 3
Year 4
 Conventional crop rotation:
 Wheat  Lupin  Wheat  Lupin
Table 1: Crop rotation and herbicide use over the four-year field trial at Beverley, WA
 High ALS herbicide use
 Triasulfuron/metosulam  Simazine / metosulam
 Triasulfuron / metosulam
 Simazine / metosulam
 Low ALS herbicide use
 Triasulfuron / 2, 4-D
Simazine / metribuzin + diflufenican
 Triasulfuron / 2, 4-D
 Simazine / metribuzin + diflufenican
 Alternative crop rotation
 Wheat TT canola
Wheat
 Lupin
 High ALS herbicide use
 Triasulfuron / metosulam
 Simazine / atrazine
 Triasulfuron / metosulamn
 Simazine / metribuzin + diflufenican
 Low ALS herbicide use
 Triasulfuron / 2, 4-D
 Simazine / atrazine
 Triasulfuron / 2, 4-D
 Simazine / metribuzin + diflufenican

FIGURE 1 Impact of crop rotation and a high or low frequency of ALS herbicide applications on the build-up of ALS resistance in a wild radish population in the WA wheatbelt over four years.

Image of a graph showing the impact of crop rotation and herbicide on wild radish application in WA

SOURCE: Department of Agriculture and Food, WA

More information:

Abul Hashem, DAFWA,
08 9690 2000,
abul.hashem@agric.wa.gov.au

Next: Use full rate to prolong life
Previous: Selective spraying to cut costs

GRDC Project Code DAW535

Region West, South