Crop Watch VIDEO: Dry weather spraying dilemma

Some farmers in the east have stopped drilling after the recent spell of unusually hot weather, waiting for rain to return. And herbicide programmes have also been tweaked due to the heat.


“The hot dry weather has caused many questions to be raised about crop management,” said Cambridgeshire UAP agronomist Will Foss.

Seed-bed quality had declined since mid-September as soils dried, but pre-emergence herbicide applications had continued, except where seed coverage was inadequate.

Some farmers were now waiting for rain before continuing to drill. “If seed is going to be sown into dry seed-beds then rates should be based on likely emergence date and not on drilling date.”


Where possible, any post-emergence herbicide use, especially programmes based around CTU co-formulations, would be delayed until crops had hardened off and the unseasonal weather had passed.

Nick Brown of ProCam said while seed-bed quality was exceptional, the performance of any flufenacet-based programme was likely to be compromised in warm and dry conditions.

Defy (prosulfocarb) had performed better in the dry, he explained. “I have tended to go for four litres/ha of Defy with 0.4 litres/ha of Liberator (diflufenican + flufenacet), rather than 0.6 litres Liberator plus two litres of Defy. The worst fields have received full rates of both.”

Yorkshire AICC agronomist Patrick Stephenson said it’s the first time he had questioned whether it was too hot to spray in October.

“Common sense dictates that chemical degradation and volatilisation is likely to increase, but with only a limited spray window spraying has continued.

“Early-drilled crops are now emerging and many will be receiving peri or early post-emergence treatments. Flufenacet provides the backbone of the early spraying regime and we hope control will be as good as last year.”

Slugs were noticeable by their absence and with rapid emergence he hoped the highest risk period was past. “This should help minimise the amount of metaldehyde used this season, helping protect this useful active.”

Neil Potts of Matford Arable said farmers in mid-Devon had welcomed a week’s fine weather.

“Mid-September saw the ground so wet that some growers were beginning to fear they might not get crops drilled, let alone finish combining.”

But just a few miles away around Exeter growers were struggling to plough ground because it was too dry, he added.

Most barley and wheat crops were receiving a pre-emergence herbicide immediately after drilling. However, some growers busy drilling had missed the pre-emergence application.

“Care needs to be taken if a peri-emergence application is planned. Emerging crops are going to be extremely lush and tender and very prone to herbicide scorch. Choice of active and timing of application will be key to minimising damage.”

Despite most soils being drier than normal during tuber initiation there were reports of black dot development on high-risk packing crops, probably caused by early canopy senescence, reported John Sarup of Spud Agronomy.

Crops should be assessed at harvest for black dot infection. First signs were sclerotia (tiny black dots) usually seen in patches near to stolon attachment to the tuber.

“If the infection has not progressed further than this at harvest, rapid pull down to below 4C within a month should minimise further development.

“If the tuber skin has already started to discolour then temperature control will not be able to prevent further disease development and early crop movement will be needed to meet quality standards.”

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