Efforts against blackgrass can let in wild oats
Efforts against blackgrass can let in wild oats
By Andrew Blake
BE extra vigilant for wild oats this spring, warns Banks Cargill agronomist Rob Farrow.
The chances are that the yield-robbing grass weeds could catch out more growers than usual because of the shift in autumn herbicide use.
Most people see their number one autumn target as blackgrass, says the East Anglian-based expert. As a result, growers have been switching to more blackgrass-effective programmes, like Crystal (pendimethalin + flufenacet) followed by Lexus (flupyrsulfuron)/ Stomp (pendimethalin).
But these combinations are not controlling wild oats as well as the more traditional Avadex (tri-allate)/isoproturon sequences. "They have less activity on wild oats, which has opened the door for heavier infestations."
Control of highly competitive winter germinators has only been adequate when Hawk (clodinafop-propargyl + trifluralin) has been used, says Mr Farrow.
"It takes only two wild oats/sq m to cut yield by 2%." The cold snap over the New Year will have helped finish off wild oats receiving a robust autumn treatment, but recent milder weather means there could be many partially controlled plants needing an early spring spray.
Provided there are no more than 2-3/sq m at the end of crop tillering, it should pay to wait to clean up any spring germinators with a later spray, he advises. But high populations will merit treatment as soon as the weather starts to warm in late February and March.
"People with abundant winter wild oats really have to be prepared to treat, even if it is only to patch spray the worst areas."
In wheat, the most cost-effective choice is Topik (clodinafop-propargyl), suggests Mr Farrow. "Up to the end of tillering, a dose of 100ml/ha should be enough.
"But if you are patch treating you will probably have to wait until you can see the oats above the crop. By then you will need the full 125ml/ha rate plus oil."
Besides killing wild oats, full rate Topik will control non-resistant blackgrass for an overall cost of £17-18.50/ha (£7-7.50/acre).
Cheetah Super or Triumph (fenoxaprop-P-ethyl) cost much the same. "They also have a bit more flexibility on doses for wild oats if you can hit them at the best timing.
"In my view, Topik is better on blackgrass, unless you have fop-resistance."
Avenge (difenzoquat), a one-time prime wild oat killer, is no longer as effective as these more modern herbicides, he says. "I wouldnt recommend it.
"Spring germinating wild oats are less competitive than their winter cousins, but still merit treatment if there are more than about 3/sq m."
Wild oats in barley are generally less troublesome because the crop is more competitive than wheat. But for those that need tackling Corniche or Tigress Ultra (diclofop-methyl + fenoxaprop-ethyl) is the answer, says Mr Farrow.
"Once the oats get quite big you need 1.5 litres/ha – the full rate for blackgrass is 2 litres."
In general, it pays to keep water volumes up to ensure good spray coverage, he advises. *
• Switch in autumn herbicides.
• Less effective oat control.
• More to tackle in spring.
• Early sprays could be needed.