Wild oats Knowledge Hub

Some of the most familiar weeds, both wild oat and winter wild oat are tall, stout annual grasses similar to cultivated oats. Very similar in appearance, both have a large loose drooping seed head or panicle. Wild oat is 30–150 cm tall and germinates in both autumn and spring, although most seeds germinate in the spring. Winter wild oat is a stouter plant 60–180 cm, which germinates in the late autumn and winter.

It is very difficult to tell the species apart, but there are subtle distinctions. Wild-oat differs from winter wild-oat in the following areas; leaf margins are hairier near the base, spikelets are smaller, lemmas are broader and end in two small teeth. The two species are easier to tell apart when ripe, wild-oat seeds separate from the spikelet with no scar.

Both species may occur within a single field, sometimes in a mixture but sometimes in discrete, separate patches. Apart from the typical germination period, there are no major physiological differences which significantly affect responses to cultural and chemical control methods (unlike brome for instance). Hence, ‘wild oats’ is a catch all term which generally refers to both species.

More information on identifying wild oat species

Because they produce fewer seeds per plant, wild oat infestations tend not to build-up as fast as those of other annual grassweeds. However, their highly competitive nature means that even small populations can be extremely damaging, and reduce yield.

At the same time, the pre-emergence herbicides increasingly being relied upon for annual grass weed control in cereals tend to give limited control of wild oats because many plants may only emerge in late autumn and spring.

Optimum cultural controls and the ideal timing for wild oat herbicide control may well conflict with the best timing for controlling black-grass, Italian ryegrass and bromes. Mixed populations may, therefore, require herbicide strategies involving both early autumn and spring post-emergence treatments.

Delaying post-cereal harvest cultivations for as long as possible will allow freshly-shed wild oat seeds on the soil surface to lose their viability through germination, predation and fungal attack, the longer the delay, the greater the benefit. Incorporating freshly shed seed can induce dormancy for up to six years.

Rotational ploughing is generally less effective at controlling wild oats than other annual grassweeds both because they can emerge from greater depths and as it is more likely to bring longer-lived seeds back to the surface.

Delayed drilling is also less effective, because of the weed’s protracted germination pattern, although it may have some benefit in making wild oat seedlings more sensitive to frost.

Spring cropping is an effective control for wild oats particularly later sown spring crops which are drilled after the first spring flush of wild oats is sprayed off. In earlier drilled crops, wild oats are likely to be more of a problem so consider residual herbicide protection (e.g 0.3 l/ha Liberator) for cereals.

Crop competition

In their early growth stages wild oats are very susceptible to competition, so competitive crops like winter oilseed rape and winter beans can be very valuable in assisting other control measures. They also allow actives like clethodim and propyzamide to be used for control.

Late-spring sown crops like peas and linseed can also help by allowing the greatest possible time for pre-planting destruction with Roundup while, potatoes and sugar beet offer both this and useful in-crop chemical or mechanical control opportunities

In winter cereals, Liberator (flufenacet + diflufenican) and tri-allate are the best options where autumn germinating wild oats are a problem. Because of protracted germination, it is likely that a spring applied post-emergence herbicide will be needed to deal with problems in spring. The best option depends on the other grass-weeds and broad-leaved weeds in the population, options include Atlantis Star (mesosulfuron + iodosulfuron + thiencarbazone), Pacifica Plus (mesosulfuron + iodosulfuron + amidosulfuron), pyroxsulam, clodinafop and pinoxaden.

In winter oilseed rape and beans, propyzamide and clethodim are the main herbicide control options.

Relying exclusively on HRAC Group 1 (ACCase) and Group 2 (ALS inhibitors) does create a risk of resistance developing. Ensure other active groups are used for wild oat control across the rotation and make full use of cultural controls.

Thanks to their large size, identifying wild oat patches is straightforward in late spring. Hand-rogue or spray off with glyphosate in early June before seeds start shedding.

When hand-rogueing, whole plants must be removed rather than merely seed heads to avoid regrowth and subsequent seed shedding. Even very green, unripe seeds are viable and should not be discarded in the field.

Although labour intensive, both hand rogueing and patch spraying are likely to be justified by the extent to which they limit weed seed return and the yield impact of even relatively low wild oat populations.