Monday, September 16, 2019

Care and good strategy vital to establish crops

September 10, 2019 by  
Filed under Crops

Newly drilled crops need nurturing well this month to get them off to the best start, says Richard Overthrow.

Oilseed rape drilling started as early as late July as growers took on board – perhaps to the extreme – last season’s experiences. Earlier sowing definitely helped with flea beetle last year but as stressed before, in previous years later sowing has helped.

Therefore, for anyone with rape still to sow, these crops have an equal chance of escaping the worst flea beetle attention so don’t be too concerned. That said, mid-September is the end of the rape drilling window so hopefully most crops are in.

Emerging crops  will need constant monitoring for flea beetle, aphids, slugs and early phoma infections. The earliest sowings may have already been treated for one or more of these, but hopefully a minimum of re-drilling has been done. This was almost the norm last year but hopefully we have learned from such experiences.

If aphids move into small crops, before the four-leaf stage, then any virus they introduce can reduce yield so treatment would be necessary, although obviously TuYV resistant varieties won’t need this. Remember the aphid vector concerned is resistant to pyrethroids, so treatment will not be cheap.

Crop protection

Early phoma may also be an issue, again more likely on the early sown crops. If it appears in September, and reaches threshold,  it will need treating. If it doesn’t develop until next month then treatment will be achieved by a standard autumn fungicide, i.e. one autumn spray rather than two.

Where weed control in rape was delayed to allow assessment of crop establishment then, if the plan is for  the early residual products (metazachlor etc), these should be applied soon, they work better at pre-emergence of the target weeds.

Alternatively, Belkar can be applied a little later (from the two-leaf stage) or if broad leaved weed pressure is not too high, treatment can wait for the later propyzamide or carbetamide timings.

Keep an eye on volunteer cereals in rape crops; once these reach the two-leaf stage they become particularly competitive and should be removed by then. The main damage is competition for moisture and this may already be short.

Wheat and barley

Winter cereal drilling may start this month though in general sowing dates have been retreating due to grass weed strategies, disease pressure reduction and now of course, barley yellow dwarf virus management.

For the latter, wheat, barley or oat crops sown before the end of this month will need at least two pyrethroid sprays, even if the AHDB thermal time system is followed, to control aphids and if this is done over a wide area resistance will be encouraged.

Of course, if large acreages are to be sown then it may be too risky to set a start date of, say, October 1st, but only wheat crops going into fields with no grass weed problems, and of varieties with good disease and lodging resistance, should be sown in September.

Winter barley should be drilled towards the end of this month or early October, since sowing beyond that would reduce the crop’s potential significantly. Oats are more suited to October than September sowing.

Metaldehyde

Slugs will need to be monitored carefully in all autumn crops but only treated if damage is seen or slugs are found in bait traps. Growers may still be using metaldehyde this autumn following its reprieve but stewardship guidelines should still be followed and ferric phosphate is still the preferred product.

The importance of good seedbeds to pre-emergence herbicides cannot be underestimated for grass weed campaigns. Most products are susceptible to dry and cloddy – or wet and cloddy – seedbeds. If it takes a little longer to create a good seedbed then hold off and get it right.

There is a close positive correlation between pre-emergence herbicide performance and autumn rainfall so much of it is out of our hands but if possible let soil moisture and seedbed quality dictate crop sowing date where residual herbicide performance is important.

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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