Perfect Storm for Wild Oats

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Wild oat numbers are on the increase –the number of wild oats standing in fields this harvest confirms this – so why is this and what can be done to get on top of this competitive grass weed.
With a focus on black-grass over recent years, wild oats have become the forgotten enemy,” says Ruth Stanley, country manager for off-patent manufacturer, Life Scientific. “But it’s actually our most competitive grass weed, on a potential yield loss/plant basis.”

“Just one wild oat plant/m2 can reduce yields by as much as 1t/ha in winter cereal crops, and 0.6t/ha in spring cereals. Wild oats also act as hosts for pests and diseases, such as barley yellow dwarf virus.”
There are two species of wild oats that are weeds in the UK – the common wild oat and the winter wild oat.
The common wild oat (Avena fatua) is an important weed in all parts of the UK and grows in most soil types, causing problems in winter and spring crops. A second species, the winter wild oat (Avena sterilis ssp. ludoviciana) is becoming more widespread and increasing in number. Both species are capable of germinating in winter or spring.

“This increase in wild oats comes as a result of several factors,” she explains. “Min tillage or direct drilling doesn’t bury wild oat seed, burial increases dormancy so seeds left on the soil surface are more likely to germinate and thrive.“

“There has also been a reduction in the use of ALS chemistry traditionally used to control black-grass, but growers worried about reliance on this chemistry for black-grass control have forgotten that these herbicides are actually very effective at wild oat control.”

Last year Life Scientific and NIAB worked together to conduct a UK wide wild-oat herbicide resistance survey – the first one in over twenty years. 105 wild oat seed samples were sent in by growers and were screened for resistance to Axial Pro (Pinoxaden) and Niantic (Iodosulfuron/mesosulfuron) at field rates.
“The results pointed to cases of resistance in both species to both Axial Pro and Niantic, with the study confirming that the occurrence of resistance is higher in the winter wild oat (Avena sterilis ssp. ludoviciana).

“For winter wild oat populations specifically, the resistance to ALS or ACCase chemistry is the same, but in spring wild- oat populations resistance to ACCase is double that of ALS chemistry.”
These are important messages for the industry, she says. “Although we’re getting more and more reports of wild oats as a problem weed, we know from these survey results and the resistance testing, that ALS chemistry such as in the herbicides Niantic in the autumn and Cintac in the spring, are still effective on wild-oats and have a valuable place in the herbicide programme to provide efficient control. “

“That said less than 20% were resistant to ALS chemistry, and these were from growers who thought they had resistance issues anyway, so the emphasis is still to ensure correct product application to prevent decreased sensitivity in the field in order to get the best performance from these herbicides.”

However, where ALS chemistry is not being used, or ALS resistance may be a concern, it is possible to use a herbicide such as Kipota (240 g/l clodinafop-propargyl and 60 g/l cloquintocet-mexyl, EC) which is a reverse engineered version of Topik. Kipota can be used anytime from when the crop has established up to growth stage 41.

In recent trial work with NIAB, the activity from Life Scientific’s Kipota on susceptible oat populations is shown to be comparable to Topik, which is the very premise of the concept of reverse engineering an off-patent product from its original reference product.

PANEL
Key factors to consider for wild oat management
• Identifying and understanding more about the two differing wild oat species on their own farm.
• Making better use of existing products to maximise their potential in-field – getting the application timings right relative to growth stages and conditions.
• Herbicides and rotating active ingredients- there is relatively low-level of cross-resistance between herbicides in both species, so this approach will become increasingly important.
• Adopting some element of cultural control in order to supplement and sustain the control achieved by herbicides.

1. Timing
Weeds should be actively growing
Consider temperature and moisture
1-2 leaves
2. Dose
Use maximum rates (0.4kg/ha Niantic or 0.5kg/ha Cintac)
Add authorised adjuvant
3. Application
Match nozzle to the conditions
Keep boom height at 50cm above target
Forward speed of 12-14kph

 

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About Author

Editor of Agronomist and Arable Farmer as well as responsibility for the Agronomist and Arable Farmer and Farm Business websites. After 17 years milking cows on the family farm John started writing about agriculture in 1998 and has since written for a variety of publications and has developed a wide circle of contacts within the industry. When not working John is an avid follower of Stoke City.