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A dry period during November helped ease fears of another wet autumn, says Richard Overthrow. Surprise dry spell eases fears of wet autumn

A dry period during November helped ease fears of another wet autumn, says Richard Overthrow.

Despite thoughts last month that most will have given up on drilling until spring, a brief dry spell allowed some more to be done and many completed their winter cereal programme, even putting in all their bean acreage.

The later sown cereal crops shouldn’t need as much herbicide input as earlier sowings which is just as well given that spraying opportunities are rare at this time of year and in many cases drilling was just possible but subsequent spraying not.

Many of the residual products can be applied early post-emergence but some have a latest application date of the end of this month – check this if still hoping to treat.

It’s worth stressing again that the level of herbicide input need not be high for these later sowings and a complex stack could compromise crop health anyway, reducing its competitive ability.

Trade-offs

In NIAB TAG trials we regularly see a negative trade-off between herbicide input and crop strength in this way, leading to more grass weeds from higher herbicide input with later sowings.

There have been issues with some of the winter bean crops sown where pre-emergence treatment is almost the only option but again for many, good conditions for spraying as well as for drilling was asking a bit too much.

Products like propyzamide and clomazone should not be applied post-emergence; carbetamide is the main option for post-emergence treatment at this time of year.

In cereal crops we should be wary of any mild spells in December that might kick-start aphid activity, and virus spread. That said, conditions throughout the main flight window were not good and numbers of resident aphids will be low.

It’s generally only the September-sown wheat and barley crops that attracted significant numbers and these are likely to have been treated.

Warm soils

Soil conditions are more or less suitable – temperature-wise if not travel-wise – for propyzamide application to oilseed rape and even if not, few growers are prepared to wait much beyond the end of November to apply it.

There was one recent season when the appropriate soil temperature didn’t occur until March, so some compromise is often necessary. Applying to warm soils in September and early October will shorten the active’s useful life but even if soils are warm now we should get sufficient persistence from it.

Early phoma infections were treated but in many rape crops these have only appeared recently and these are unlikely to form yield-robbing stem cankers, hence any late autumn fungicides should target light leaf spot, if this is required.

Flea beetle

Crops should also be checked carefully for presence and numbers of cabbage stem flea beetle larvae, not with a view to treating as nothing is effective, but to have an idea of likely damage and hence yield potential and level of justifiable expenditure from this point on.

It goes without saying that fields destined for spring cropping may also be a little wet now so should be left alone.

Winter cultivations, even winter spraying-off, rarely helps and with the equipment available today leaving these operations until just prior to sowing can be just as effective in terms of cleaning up weeds and preparing seedbeds.

  • Richard Overthrow is a regional agronomist with NIAB TAG, the UK’s largest independent agronomy organisation with several research centres in the Midlands. For more details, call 01223 342495.

Timely tips

  • Watch for issues with winter bean crops
  • Mild weather can trigger in cereals
  • Check latest application dates for sprays
  • Adjust herbicide levels for later sowings
  • Check rape for cabbage stem flea beetle