Avena sterilis L. ssp. ludoviciana (Durieu) Gillet & Magne, (A. ludoviciana)
Annual Grass Weeds
Winter wild oat is an introduced annual grass weed of arable, waste and rough land usually on heavy soils. The winter wild-oat has a more local distribution than common wild-oat (A. fatua) and as the name suggests is a problem in winter crops. One of the first records of the species was in 1926 was from Abingdon near Oxford. In a 1951 weed survey, winter wild-oat occurred predominantly in an area within a radius of 80 miles of Oxfordshire. It became a major weed of heavy land in central, southern and eastern England but is now more scattered. In a survey of UK arable weeds in 1971-1973 it was recorded in only 2% of the crops surveyed. In a survey of weeds in conventional cereals in central southern England in 1982, winter wild-oat was found in 7% of winter wheat, 3% of winter barley and 1% of spring barley. Winter wild-oat is a troublesome weed of winter cereals in southern Europe.
Winter wild-oat is more of a weed problem in southern Europe. In Italy, it is represented by 2 subspecies, ssp. ludoviciana and ssp. macrocarpa. Also there are individuals may have resulted from hybridisation of winter wild-oat with the common wild-oat (A. fatua).
Seeds of winter wild-oat may be fully developed but dormant 15 days after flowering. Unripe seeds are viable but non-dormant. The seeds possess a hygroscopic awn that twists and straightens with changes in humidity pushing the seeds down into cracks and crevices in the soil.
Winter wild-oat germinates predominantly in winter or early spring. The most favourable temperatures for germination are between 7 and 13°C, the common wild-oat germinates better at higher temperatures. The main period of emergence is from October to March with a peak around November-December. Seedlings will emerge from seed buried 23 cm deep in soil. The seeds have greater food reserves than seeds of the common wild-oat and a higher percentage are able to emerge from greater depth.
Persistence and Spread
A proportion of winter wild-oat seed is relatively non-dormant and germinates within a few weeks of shedding. Once mixed into the soil, the remaining seeds can persist for around four years. No seeds remained after 7 years in a cultivated soil but seeds were still viable after 33 months. Winter wild-oat has a faster recruitment rate but a faster depletion rate than wild-oat. Different tillage systems, for example ploughing versus shallow cultivation, result in different distributions of seed and hence different patterns of seedling recruitment. Shallow cultivation leaves the seeds in the surface layers of soil while ploughing distributes seeds throughout the soil profile. Birds may eat more of the seeds following shallow cultivation.
Seeds can be introduced in hay or animal fodder but do not seem to survive in well-rotted manure. Less than 1% of winter wild-oat seeds that passed through the digestive system of a calf germinated in the dung.
Unripe seeds of wild-oat are viable but non-dormant. Destruction of hand-pulled winter wild-oats, even with green panicles, is therefore important.
Winter wild-oat seed will only germinate in cool conditions. It does not germinate in summer, therefore a summer fallow will not deplete the seedbank. Fallowing for a full year however reduced seed numbers in soil by 65%.
Seedlings of winter wild-oat are smaller than those of cereals but soon catch up and exceed the crop. Therefore the crop needs to be more competitive at an early stage. In winter wheat cultivars, greater straw height and dry matter accumulation were better characters for predicting competitive ability than the number of tillers that developed. Cultivations prior to spring cropping will effectively control winter wild-oat seedlings. Where winter wild-oat is a problem, a series of 3-4 spring sown crops allows the weed to be destroyed by thorough cultivations.
Leachate from the roots of wheat seedlings inhibit the germination of winter wild-oat seed, however, post-harvest residues of wheat stimulate germination of the seed. The same chemical may be responsible but at different concentrations.
Frit flies (Iscinella frit) will attack winter wild-oat as well as the cultivated oat.
Updated October 2007.