The Imtrader Ed.3 – Wild Oats A Re-emerging Problem

 

Wild Oats (Avena fatua L.) are one of the most common and widespread weeds throughout the winter cropping zones in Australia. Originating in Southern Europe, Wild Oat plants are reproductively prolific, self-pollinating and produce up to 225 seeds per plant. Allowing only a few surviving plants to set seed can lead to rapid replenishment of the seed bank. Due to a staggered germination pattern, Wild Oat plants are a weed requiring constant control.

Further complicating control of Wild Oat plants is the resistant nature of many populations to at least one herbicide group. Group A resistance was recorded with ‘fop’ molecules such as clodinafop (Topik®) and diclofop (Hoegrass®) failing first, followed by ‘dim’ molecules including clethodim (Select®) and tralkoxydim (Achieve®). There are some recent reports of ‘den’ resistant populations, specifically to pinoxaden (Axial®).

Group B resistant populations are becoming more and more prevalent including, iodosulfuron (Hussar®) and mesosulfuron (Atlantis®). Resistant Wild Oat populations are increasing across Australia, with the last option for post emergence control being the Group Z chemistries, specifically flamprop (Mataven L®).

Although Wild Oat plants are a significantly resistant weed, it does not compare to its comrade Annual Rye Grass. This is mostly due to genetics as can be seen in the table below.

Pre-emergent herbicides have generally proven to be the best stand-alone option for wild oat control when directly compared to stand-alone post-emergent options. However, Integrated Weed Management (IWM) trials have demonstrated the effectiveness in preventing resistance development by implementing a dual treatment strategy. Wild Oats exhibit around 40% germination during the autumn break (these are susceptible to pre-seeding knockdowns and pre-emergent strategies) with the remainder germinating sporadically through until spring. These later germinating populations of Wild Oats escape the pre-emergent strategy. Therefore it is vital for these later germinating biotypes to be controlled with post-emergent options to ensure optimal control, prevent seed-bank replenishment and minimise the potential for further resistance development.

Combinations of Trifluralin and Triallate are widely reported as the most effective option for pre-emergent Wild Oat control across most winter crop varieties. Imtrade’s Jetti Duo is an excellent option, registered for use in wheat and barley.

Tips for Wild Oat control;

  • Use effective Pre-Emergent Herbicides
  • Test Wild Oat seeds for resistance to ensure effective Post-Emergent herbicide use
  • Ensure correct timing of application with Post-Emergent herbicides
  • Crop rotation
  • In significant burdens brown maturing or cutting crop for hay before seed set are beneficial

 

For more information specific to your situation contact your local agronomic advisor.

References

Data from GRDC and Herbiguide,

Table: AHRI