Friday, December 6, 2019

Patience is a virtue – and goodness knows we need it

November 6, 2019 by  
Filed under Crops

A wet autumn continues to make crop establishment challenging, says Richard Overthrow.

A considerable area of winter cereals remains to be sown – despite one or two brief windows of opportunity towards the end of last month.

The weather has been so awkward during much of this autumn that many growers with drilling still to do will be questioning the wisdom of carrying on – or deciding to leave it all until spring.

Experiences in 2012/13 showed us that we can sow winter wheat in January and February and still get a harvestable crop so all is not lost yet. Not everyone will be in this situation but it’s still likely that a significant acreage of wheat was or will be sown in late October or later.

This will provide savings in inputs such as aphid sprays and weed control, but in grass weed situations it is still important that these late sown crops are well-established and as competitive as possible so they will need monitoring for bird and slug activity which might threaten this.

Winter cereals

It is too late for winter barley now, altered plans for these often involving autumn- or spring-sown spring barley, but if winter wheat is sown this month grass weed pressure will be much reduced.

For this reason, and again the crop competitiveness issue, any residual herbicide treatments should not be stacked too heavily. Too many products in a pre-emergence treatment can adversely affect crop establishment, and as said these shouldn’t be needed anyway.

BYDV control should be tailing off now: the ‘borderline’ crops which emerged only recently but in time to attract migrating aphids might still reach the 170 day-degree threshold before winter starts but these crops should be inspected regularly and only treated if aphids are present. Any cereal crop emerging now, or later, is very unlikely to be infested so no treatment would be necessary.

Oilseed rape agronomy is very difficult to discuss: perhaps not so for those who didn’t plant any or have already written crops off, but for many the decision on whether the crop should stay or not still hasn’t been made.

Quite a few crops locally made it through the adult flea beetle attacks but still carry plenty  of shot holes and with conditions last month not being conducive to growth, these crops have barely moved since. Larvae in petioles are already being reported and the final state of many crops won’t be known until the New Year.

With herbicides such as propyzamide usable until the end of January, and carbetamide the end of February, many herbicide treatments are being delayed as long as possible, and many crops haven’t received an autumn fungicide.

Control measures

The presence or absence of larvae in rape plants  should be obvious now such that any late decisions can be made, but remember there are no effective control measures for larvae so do not attempt to treat with insecticides.

That said, there are some better looking crops that saw little adult activity and hence justify investment and if not already applied these should receive an autumn fungicide soon, targeting light leaf spot and phoma.

This month soil temperatures usually become suitable for propyzamide applications, and if planned these would follow an early metazachlor-based treatment or post-emergence Belkar.

Winter bean crops will have been sown last month, either planned as such or as replacements for oilseed rape. Ideally weed control would have been done or at least started pre-emergence as post-emergence options are few. Carbetamide is one post-emergence option, being a residual that can be applied post-emergence, but ideally before target weeds, especially grass weeds, become too large. Any bean crops not yet sown can go in any time this month or later but yield potential starts to fall off from now on.

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.

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