Wild oat control in cereals

The wet conditions at the back end of last year prevented a lot of growers from applying pre-emergence herbicides to their winter cereals, so making up for missed applications will be a priority on land with a high weed burden.

For ground affected by wild oats, an appropriate herbicide programme will be crucial, especially as just one wild oat plant per m² is capable of reducing cereal yields by as much as 1%.

Unfortunately, like many other weeds, the two main species of wild oats, Avena fatua and Avena ludoviciana (sterile oat) have developed varying degrees of resistance to a range of herbicide active ingredients. Thankfully, this resistance is developing relatively slowly, but it is important to reduce the threat of further resistance by using a rotation of herbicide modes of action (ACCase inhibitors such as clodinafop and cycloxydim, fenoxaprop and pinoxaden and ALS inhibitors such as mesosulfuron).

The current level of resistance varies according to the species of wild oat present, with the more commonly occurring Avena fatua less prone to resistance than the rarer Avena ludoviciana. It is therefore important to know which species of wild oats is present, and to understand how and when the different species express peak emergence.

Timing is key

On land with a heavy wild oat burden, the first herbicide application of the season should be made as soon as conditions are conducive to effective herbicide performance: if using a clodinafop-based herbicide such as TOPIK (240 g/L clodinafop-propargyl & 60 g/L cloquintocet-mexyl) the latest practical timing for application is at GS41. Beyond this the crop canopy may have developed to such an extent that it prevents effective coverage of the target weeds.

The power of TOPIK: treated (left) vs. untreated (right).

Best practice

To achieve the best results, TOPIK must be used with care to ensure complete spray coverage is achieved: busy spraying schedules can make it tempting use a reduced water volume so that more ground can be covered within a specific window of opportunity. This is a feasible strategy when weeds are still small and not shielded by the crop canopy, but it is a poor technique to use later in the season when the crop is bigger.

As a rule of thumb, it is possible to reduce water volume prior to GS31 (using 100l/ha instead of 200l/ha), but beyond this growth stage it is advised that a water volume of at least 200l/ha should be used. There is however some evidence to suggest that smaller droplets and a concentrated solution using 100l/ha will perform well at the GS31-41 timing, but only if the wild oat plants are larger than the crop and therefore emerging above the crop canopy.

Irrespective of when it is applied, TOPIK will perform best when used during good growing conditions for the target weed as this improves product uptake. In contrast, cold and dry conditions will impede the efficacy of all ACCase herbicides, even when applied at the optimum timing for wild-oat activity. 

Spraying tips

Nozzle choice, boom height and forward operating speed all effect spray coverage, as do nozzle choice and angle. The simple advice when spraying for wild oats is to:

1. Spray slowly (maximum 12pkh)
2. Spray at a sensible boom height (50cm above the canopy)
3. Use an appropriate water volume (200l/ha after GS31) 
4. Select a nozzle type and angle to target weeds beneath the crop canopy.

Reducing sprayer forward speed from 16kph down to 12kph is just one of the considerations needed to maximise wild oat control. Water volume, boom height and nozzle choice are also key factors, especially when tackling weeds protected by a thick crop canopy.

(Photo credit: Syngenta forward speed trial on TOPIK)

TOPIK: growth stage application recommendations

TOPIK (240 g/L clodinafop-propargyl and 60 g/L cloquintocet-mexyl)

Controls wild oats, rough meadow-grass and gives moderate control of Italian rye-grass in wheat, durum wheat and triticale.

Optimum timing:

Wild-oats from 1 leaf unfolded up to flag leaf ligule visible.

Application rates:

0.25//ha

0.125//ha plus a suitable adjuvant (e.g. methylated seed oil)

Optimum weed control is best achieved when all the wild-oats have emerged and are actively growing in good conditions. More information here.