Growers across East Anglia are being urged to prioritise wild oat control this autumn following one of the worst years for infestations in recent memory,
Wild oats plagued many cereal crops last season – due to particularly difficult conditions for spring post-emergence and uncompetitive cereal crop canopies. Herbicide resistance also played a part, say experts.
“The cold, dry spring meant there was little active weed growth in the main 2021 post-em spraying window,” says NIAB specialist John Cussans. “Then, when the weather warmed-up and we got some much-needed moisture, later-sown winter cereals were decidedly thin and uncompetitive.
“This was an open goal for both already established and later-germinating wild oats. The fact that these can complete their life cycle in just a few weeks means a big seed return which must be managed this autumn rather than delayed until next spring.”
Problems have been exacerbated by the increasing incidence of the winter wild oat subspecies alongside the traditional and common spring wild oat, says Mr Cussans. Herbicide resistance developed quicker in winter wild oats than spring varieties, he suggests.
Winter wild oats are also more likely to emerge in the autumn rather than spring. Their large and aggressive root systems mean they typically have double the impact on cereal yields as later-emerging plants – making the earliest possible removal crucial.
Although immediate post-harvest cultivation can help to flush out blackgrass, Gowan weed management specialist Barrie Hunt says it can result in wild oat populations that are for or five times higher than the best no-till regimes.
“Although it’s a very competitive weed – five plants per square metre typically cause a 5% wheat yield loss – wild oats don’t suffer competition well either,” says Mr Hunt.
“This makes the most competitive crop canopies important in managing it,” he adds.
“Unfortunately, that is not what we usually get with blackgrass management strategies that delay wheat drilling into late October – especially when seedbeds are less than ideal, winters are wet and cold, dry conditions restrict spring growth.”
The focus on blackgrass means wild oats have become the forgotten enemy over recent years, says Ruth Stanley, country manager for agrochemical manufacturer Life Scientific. “It’s actually our most competitive grass weed, on a potential yield loss per plant basis.”
Just one wild oat plant per square metre can result in a 1t/ha yield loss in winter cereals and 0.6t/ha in spring crops, says Mrs Stanley. Wild oats also act as hosts for pests and diseases – including barley yellow dwarf virus.
A reduction in the use of ALS chemistry to control blackgrass has helped to fuel a resurgence in wild oat populations, says Mrs Stanley. Growers had forgotten that these herbicides are actually very effective at wild oat control, she adds.
ALS chemistry still had a valuable place in control programmes. But it was important to prevent decreased sensitivity in the field by ensuring the correct products were applied – and to get the best performance from ALS herbicides.
Five tips to combat wild oats
- Leave stubbles uncultivated. A three-week gap or longer after harvest will maximise weed seed predation – and help combat meadow or rye brome too.
- Go no-till or full plough. A true no-till regime will ensure greatest predation, while full inversion will bury weed seeds below 20cm. Shallow tillage is the worst of both worlds.
- Encourage dense cereal canopies. These compete especially well against emerged wild oats and suppress late germination. Avoid late wheat drilling if you can.
- Clean machines and seed. Good biosecurity will help prevent the spread of wild oat seed – both within and between fields – by combines, balers and farm-saved seed.
- Use a herbicide. Avadex can be invaluable against wild oats germination. So too can ALS chemistry or Kipota, a reverse-engineered version of Topik.