Forward oat crops take a hit

By Andy Doyle

Some autumn sown oats crops appear to have suffered badly from weather effect in recent weeks, probably frost. The damage is most severe on very early sown or soft crops. Main stems appear to have just rotted away but this is not the typical frost damage symptom that was observed in some previous years.

The damage is not uniform across fields, or areas, and it appears to be worst in early drilled fields and on soil types that supported good growth in the backend.

Fields on fresher ground, or fields that had received manure/sludge in the autumn, appear to be the worst affected. It would seem that there is damage to all crops but this may not be either readily visible or significant.

The symptoms range from totally dead stems to stems with all the leaf sheaths dead but the stem still appears to be intact. Occasional stems showed a dead panicle in the stem with rot commencing.

The second consequence of the problem is that there is a flush of new tillers emerging in response to the damage to the main stem. These could well play havoc with the ability to deliver quality grain in the harvested sample. With winter oat plantings up considerably, it is inevitable that quality will be a big issue in the market next harvest. The presence of large numbers of late tillers - that will carry heads and grains - are likely to have poorly filled grains which will drag down grain the quality at harvest.

The likely effect of the damage could be categorised as minor, substantial and severe. The minor damage can be seen in most fields and involves some loss of main stem with very few late tillers. The 'substantial' crops may not suffer that much on yield because there is probably less than 20% damaged stems in crops, which are more than thick enough to begin with. However, the overall effect is likely to be much greater because of the amount of secondary tillers now emerging through the crops.

Tillers

The 'severely' damaged crops would have over 60% damaged plants with an abundance of new tillers beginning to appear in the crops because of the destruction of apical dominance in the main stem. Damage is seldom uniform within a crop but, in the very badly affected spots, all the green leaf is now from tillers. These crops are likely to be clobbered on both yield and quality and so are not worth leaving in the ground. Previous experience of this level of damage would suggest a yield of less than 2.5 t/ac coupled with a KPH from 45 downwards.

Of the visibly damaged crops I saw earlier this week, about 15% had suffered severe damage but over 60% had substantial damage. It is obvious from reports that damage is variable around the country.

Early planted, crops of spring oats in the autumn run the risk of being very advanced post winter, with the developing ear pushed up inside the leaf sheaths by the extending stem. Once the developing ear is above ground, it is much more subject to late frost damage.

On previous occasions, the main symptom was a brown or dying head a few weeks after the frost. But this is not exactly what is happening this year. The first visible symptom was that many of the fully emerged leaves were lying prostrate and not carrying their usual erect appearance. This could be seen on both healthy and unhealthy plants and was more likely a direct result of the severe winds.

The serious damage was found on the stems. A proportion of the original main stems were either dead or very unhealthy. Many carried a lot of dead or rotting leaf sheaths and leaves. This may well have been a direct effect of frost, or it may be secondary infection by Microdochium nivale or other fusarium species, following some initial frost damage. These are the snow-mould fungi and it is less than certain whether the fungus is the chicken or the egg in this situation.