Friday, October 19, 2018

Care for crops begins in earnest

March 19, 2013 by  
Filed under Crops

Crops will be requiring more attention as the weather warms up, writes Richard Overthrow.

First nitrogen doses on oilseed rape and cereals should be complete by now – particularly on the backward and late sown crops – and later this month final doses can be applied to rape and malt barley.

There are few if any excessive rape canopies this year so there is less need to restrict nitrogen doses to manage these. Second or main doses to other winter cereals should wait until next month, but if drought threatens make it early in the month, even to the later sown or backward crops.

Many oilseed rape crops will not have received an autumn fungicide, so there will be more candidates for treatment at stem extension. This has not been a routine timing in recent years but even the more backward crops might suffer if the only fungicide they receive is at flowering (bearing in mind few crops will warrant a growth regulator fungicide treatment this year).

Pollen beetle may also appear around the yellow bud stage. The increasing threat of pyrethroid resistance in this pest may make control more expensive than it has been, so check thresholds before deciding whether to spray.

Once the crop starts to flower, damage to flower buds should cease, but again considering the backward crops, these may have a prolonged green/yellow bud period so could be at higher risk from the pest.

The main spray input for this month on winter wheat and barley is chlormequat-based growth regulators. This is not a routine input on winter barley, only the most lodging-prone crops need more than a later-season ethephon-type spray.

Chlormequat is a routine treatment for nearly all winter wheat crops, however, even for the backward crops. Used alone it contributes significantly to a lodging control programme and may be all that’s needed for stiff varieties on light soils, or any late sown crop. These first treatments should be applied around GS30-31.

Oats will also benefit from routine chlormequat treatment (where contracts allow this input) though this is usually applied around GS32 and hence likely next month rather than this.

Towards the end of this month winter barley crops may reach GS31 and therefore receive their first (T1) fungicide. Most crops with reasonable yield potential will justify treatment with SDHI chemistry, for others a  triazole with either strobilurin or cyprodinil should suffice.

Wet weather diseases (rhynchosporium, net blotch) usually dominate at this time so products chosen should have good activity against these.

Early developing wheat crops may reach the T0 fungicide timing this month. This spray is becoming routine particularly following experiences last season. Even if disease pressure is low, a T0 spray also gives insurance against the effects of a delayed T1, should weather conditions or other factors compromise this next timing.

Some spring barley crops will be through the ground now and again, with drought risk in mind, make sure the nitrogen top dressing is completed soon, if not already applied. For those still to be sown then all the nitrogen should be applied as soon as possible after drilling.

At the end of the month spring oilseed crops (rape and linseed) can be sown, but as discussed before, in order to compete with weeds and tolerate pests, both need to emerge promptly so don’t plant before there is evidence that soils are warming up.

When either crop is sown, apply most or all planned nitrogen dose soon after drilling, again to reduce the effects of drying soils on successful uptake and utilisation.

Emerging spring bean and pea crops should be checked regularly for pea and bean weevil activity and treatments applied if widespread leaf notching is seen.

Richard Overthrow is membership services manager with NIAB TAG,the UK’s largest independent agronomy organisation with several research centres across East Anglia. For more information about NIAB TAG services and advice, call 01223 342200.


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