How mapping and testing can help tackle wild oat problems
Where growers are experiencing higher levels of wild oats, this is most likely due to cutbacks in use of herbicides such as Atlantis (mesosulfuron + iodosulfuron), due to concerns over lack of efficacy for blackgrass control, says independent weed scientist Stephen Moss.
“This has taken the focus away from controlling wild oats [where these products are still effective],” adds Dr Moss.
Despite concerns 20 years or so ago that resistant wild oats would become much more prevalent, this has not materialised to the extent anticipated, he says.
“Resistant wild oats are widespread in the UK but did not build up as quickly as blackgrass.
However, that could change, so farmers should be on their guard and take action to keep populations in check.
Wild oats are one of the most competitive weeds and resistant types occur in 18 countries worldwide.” Where the resistance status of wild oat populations is unknown, plan ahead and consider having a resistance test done this summer, says Dr Moss.
“Black-grass is crosspollinating so resistance can be transmitted in pollen, but with wild oats this is not an issue as they are self-pollinating.
Seeds can move but populations do not build up as quickly and wild oats are often confined to patches.”
Mapping patches and rogueing or spraying off before shedding can help to get on top of the problem, he adds.
“If you know you have wild oats in certain fields do not ignore them – seed lasts quite a long time in the soil.
If you’ve had problems in the past, give priority to fields where more wild oats come up and treat with an appropriate herbicide in spring.
“In summer it is about mapping where the wild oats are.
More farmers should map where weeds are in June and July so they can focus management on those areas.
It is imperative with any grassweed that prompt action is taken to contain the problem, otherwise the patch becomes the field.” For a ‘low tech’ option, Dr Moss suggests using the what3words app, which allows mapping of three-metre x 3m patches and using a knapsack sprayer to treat affected areas.
“While some farmers do spray patches off, it can be haphazard and often they do not record the location.
Many farmers do not use GPS technology as well as they could do, particularly when weeds are confined to patches.
More accurate mapping allows weed patches to be targeted for control in successive years, which is the only way to drive down populations.
“If there is more pressure to reduce pesticide use and cut costs, targeting patches can prevent an epidemic in the whole field.” Where wild oat populations are low, hand rogueing can be very effective, says Dr Moss.
“Even in fields with patches that are too thick to hand rogue, it is still worth hand rogueing the rest of the field.
By doing so, you can stop most of the field becoming infested.”
When controlling wild oats with herbicides in spring, Dr Moss recommends not going too early.
“Make sure weeds have emerged and are actively growing.
This could be March, April or May depending on the product and weather.” He suggets products such as Broadway Star [pyroxsulam + florasulam] and Axial Pro [pinoxaden] in winter cereals.
“Avadex granules are a good choice in spring cereals and some other spring-sown crops.
In oilseed rape and beans, graminicides such as Falcon or Pilot can give good control – provided populations are not resistant.”