Crop Watch: Hungry wheat crops and OSR crop failures

It’s take-off time as crops are now moving, with oilseed rape approaching flowering and hungry wheat crops ready for their nitrogen fertiliser. 

Thoughts turn to disease control and growth regulation strategies in wheat crops. However, as one agronomist says, the T0 is not compulsory: it is a management tool to protect the emerging leaf 4.

Oilseed rape continues to be a headache, with flea beetle larvae preventing growth in affected plants. Its future continues to be debated with crops still being written off daily.

East: Sean Sparling

AICC/SAS Agronomy (Lincolnshire)

Sean Sparling

Sean Sparling

With only 34mm of rain between Christmas Eve and 2 March, we were all getting nervous in the dry here. However, since 2 March we’ve had 56mm of rain and crops are beginning to respond well to mineralised nitrogen and a welcome drink.

Nitrogen on winter cereals now takes priority, and 8.2C soils mean we have lift-off and demand is outstripping supply in untreated fields. Septoria and yellow rust are widespread on old leaves, with September drillings noticeably dirtier than the same varieties drilled late October onwards.

See also: The secret to Norfolk farm’s record-breaking sugar beet yield

As March progresses, thoughts are turning to the T0, a fungicide application which – despite the media and industry hype – is not actually compulsory!

Use T0s purely as a management tool to protect the emerging leaf 4 from the spread of septoria and rusts or where varietal failings and established disease levels dictate the need. Prioritise those crops which clearly need help now.

Chlorothalonil should form the basis of the T0 with either an azole or a strobilurin to dry out any rust – it doesn’t need to be expensive because cheap doesn’t equal nasty at T0.

Oilseed rape

In oilseed rape, light leaf spot sprays are under way due to increasing levels over the past week. Cabbage stem flea beetle larvae numbers are staggeringly high and more widespread than I’ve ever seen.

Fields are still being written off daily as the larvae overwhelm their hosts and, with 5-10 larvae per plant relatively common, how much more damage they’ll do before pupation remains to be seen.

Is this the beginning of the end of OSR? I’d guess it is, for those who have ploughed in fields having got them to April.

No pollen beetle to worry about. It’s vital that we adhere to thresholds. We have them for a reason – remember that. Our enforced reliance on pyrethroids is a ticking time bomb, and recreational applications simply hasten the problem.     

All the spring wheat and barley is in and up, but no beet, peas, linseed or potatoes in the ground thus far. Winter may not be finished with us: March came in like a lamb and may yet go out like a lion! 

South: Iain Richards

Agrii (Oxfordshire)

Iain Richards

Iain Richards

Two weeks of “spring” last month, with temperatures topping 21C, have seen our winter crops change out of all recognition and allowed us to get nicely ahead with top dressing and make good progress drilling spring barley and beans into some decent seedbeds.

Without excessive winter wetness, our soils are nearly 3C ahead of their long-term average. So it’s not surprising that both cereal and OSR growth have responded so well to their first spring N.

We can find flea beetle larvae readily in most crops, so we still have worries on this front. But the early take-off to growth looks like helping, allowing less badly affected plants to fill in around those struggling from larger larval burdens.

While we weren’t planning any early growth regulation a month ago, we now have quite a few crops carrying substantial canopies and needing some Toprex (difenoconazole + paclobutrazol) with their prothioconazole-based stem extension sprays due to go on.

With little light leaf spot evident – in part due to the better resistance we have in our varieties these days – we’ll be taking a green bud approach to spraying our more backward, flea beetle-affected crops.

We don’t have any lodging concerns, but may well include a specialist growth regulator or metconazole to encourage greater branching and more even flowering.

Growthy wheat

Like oilseed rape, wheat has come out of the winter well-rooted and very growthy. But we won’t be confusing growth with development, going in too early with our T0s and challenging ourselves with extended intervals to T1.

Growth stage 30 is still two weeks away, so we can afford to be patient, even with the earlier drillings carrying higher levels of septoria, mildew and brown rust.

We will, however, be taking a more curative approach here, combining metrafenone, epoxiconazole and fenpropimorph or prochloraz, proquinazid and tebuconazole co-formulations with the multi-site. And including a decently strong growth regulator mix too.

In contrast, a simple azole plus multi-site T0 and a single-pronged growth regulator looks like being quite sufficient for our much cleaner, later drillings.

North: Andy Goulding

Hutchinsons (Cheshire/North Wales)

Andy Goulding

Andy Goulding

While a return to average temperatures may not be so welcome for many, the replenishment of water to the depths of our soil certainly is. The only damage from storm Gareth has been one of my flimsy fence panels.

Many autumn-sown crops are advanced. Wheat growth regulators centring on trinexapac and/or prohexadione (depending on speed of activity required) have been applied weeks ago to large crops – some which were then at growth stage 30 and even beyond (30mm from the base to ear!).

The next round of my little-and-often plant growth regulator approach is impending, with most crops still looking like they have the potential for high yield.

With tillering not finished and sufficient fertiliser applied I’m hoping to hit my target high ear number in many of my cereals this time.

Most of the winter barley is now looking a healthy colour again as a flush of new growth has smothered over the dying older tissue.

However, not all crops went too off colour – it was mainly Surge. Some fenpropimorph, manganese and a cold, wet snap would have put the mildew firmly to bed.

Patience pays

Thankfully, there weren’t too many cereals drilled in the “summer” just gone into heavy soils as the 95mm of rain that followed was not ideal for them. I’m not so fearful for the lighter land drillings.

Un-grazed grass leys have really pushed on following fertiliser application and have a resemblance to how they would usually be in the latter part of April.

A small area of early potatoes has been planted, herbicide on and put to bed with a fleece throw on.

The weather is looking set to improve substantially (depending on your rain requirements), with April forecast to be quite dry at present after the first half of the month.

My prayers are on a more straightforward year for potato residual herbicides after a challenging couple on the trot. “Rain rain go away, but make sure your back for the start of May!”

West: Stephen Harrison

Avon (AICC/Southwest Agronomy)

Stephen Harrison

Stephen Harrison

A week when the wind and rain rarely seemed to stop means very little field work has been completed. 

Spring barley drilled during the fine weather of February is now emerging and producing a satisfactory plant stand despite large numbers of corvids.

Wheat is now starting to look ready for its first dose of nitrogen and sulphur, which was understandably delayed. Few, if any, crops are at stem extension. 

Applying herbicide to winter wheat

© Tim Scrivener

No plant growth regulators will be applied until at least late March and foliar disease is not currently causing concern. 

Over-wintered wild oats may well need treatment with the first plant growth regulator. A few very high populations have already been taken care of with clodinafop.

Given the high cost of some wild oat treatments for winter barley, we tend to use a barley approved fenoxaprop product as a solo spray where required.

We had hoped to complete any remaining wheat blackgrass treatments by early March (where mesosulfuron is still working), but this now looks like dragging into this week.

The first shoots of spring germinating polygnums and umbelliferous weeds are now appearing. The problematic ones such as bur chervil need to be controlled with full rates of sulfonylureas while they are still small.

Flea beetle

Oilseed rape continues to be a headache. Flea beetle larvae are preventing growth in affected plants. 

One noticeable trend is that crops which had organic manure before planting seem to have fared better. 

The best crops are where direct drilling was combined with organic manure. Early pollen beetle seems to have been blown away!

Winter beans are in good order entering the spring and the hefty pre-emergence cocktail of propyzamide, pendimethalin and clomazone is doing a good job.

Blackgrass levels in winter oats are worrying. It is getting more and more difficult to find fields where they can be sensibly grown.

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