East: High tiller numbers could reduce winter cereal yield

It’s raining again in Lincolnshire and with spring-like temperatures; I’m getting flashbacks to 2013 when we had spring, summer, autumn, spring. The consequences of a mild winter with only half a dozen nights since November where the temperatures have dropped below freezing are clear in the field.

Starting with winter cereals, some earlier drilled crops could do with a hit of wheat bulb fly to shut down a few of the nine or 10 tillers the plants are carrying. Drillings of 200plants/sq m with just 5 surviving tillers per plant gives around 1000ears/sq m at harvest – with 650 being optimum and higher tiller numbers potentially adversely affecting yields. We can make a thin crop thicker but we can’t make a thick crop thinner with the same ease!

I’m very disappointed that Dow Agro Sciences decided to scrap the wheat bulb fly Pestwatch scheme, alongside the removal of chlorpyrifos from the cereal arena. It was, and is, a vital service to growers and agronomists alike and would have proved invaluable over the coming years as we all go back to the 1970s, where rolling and early nitrogen return as being the only way forward, alongside seed treatments.

The next significant frosty spell will no doubt trigger egg hatch, so any on-farm stocks of chlorpyrifos either need to be used up before 1 April on fields with a known wheat bulb fly history, or be returned for re-labelling. The removal of chlorpyrifos will cause grassland farmers huge problems when it comes to leatherjacket control – what happened to the assurances given by regulators that we’d never lose an active ingredient unless there was something just as effective to take its place?

There are those who have been advising the application of triazoles on cereals for the last three weeks – “to complement T0 by getting an early start on the high levels of yellow rust and septoria” that are widespread. Personally I wouldn’t waste my money on an additional “T minus 0” fungicide now – or indeed a T4, T5 or T6 later! A well-chosen and well-timed T0 fungicide will suffice.

To entertain thoughts of recreational spraying with wheat selling around £100/t, but costing around £125/t to grow seems extravagant to say the least – particularly when you’re unlikely to gain financially from such an application.

There will always be some trial somewhere that proves it’s worthwhile, but in the current financial climate, every application needs to bring a return – a well-timed and well thought out T0, T1 and T2 will – as always – be the best way to optimise both disease control and your margin.

The pre-emergence stacks have worked well, but Atlantis (iodosulfuron + mesosulfuron) applications are now underway where and when conditions allow – soils have now been above 5C for seven consecutive days and the blackgrass is clearly moving. Any success on blackgrass from contact materials is more likely in the early stages of spring growth, but get it on a dry leaf and make sure it stays dry for a couple of hours after application to get the most out of it – grandmother and sucking eggs springs to mind.

Oilseed rape hasn’t stopped growing all winter – unfortunately neither has the damned charlock in some fields. With this in mind, applications of bifenox plus oil are now being made, though it’s still too cold for Galera (clopyralid + picloram). I would always be wary of mixing anything other than the oil with bifenox, because crop effects can be unpredictable season by season and, it is after all only an Extension of Authorisation for Minor Use (EAMU). In other words, you’re on your own, so why tempt fate? In a season with growth as lush as it is, treat what is a potentially caustic product with the respect it deserves and don’t add things to the mix – where there’s blame there’s a claim!

Over the last week, light leaf spot levels have begun to increase dramatically. As we only have protectant activity against light leaf spot – at best three to four weeks at that – once it begins to reach the threshold of 1:7 plants affected, regardless of calendar date you need to spray.

I would attach a caveat though – including an insecticide for the cabbage stem flea beetle larvae, is I believe, a waste of money at this stage of the proceedings. It may only cost a couple of quid, but why spend on something that is unlikely to do any good at all? If you’re loused out with flea beetle larvae – and I’ve heard of as many as 50 grubs per plant in some regions – forget insecticide, its not going to do any good now, so put a flock of sheep on the field and let them eat the leaves. By doing so, they will take the CSFB grubs off the field with them!

Many cereal fields are now beginning to show nitrogen, magnesium and manganese deficiency as a result of wet feet and the fluctuating soil temperatures, along with diminishing mineralisation and nutrient releases from the labile pool. When you get in the fields however, the yellowing is invariably the older leaves that are still standing upright instead of being flat to the floor. In most cases, the new growth is still lush and green from the centre.

If you’re thinking of applying nitrogen to cereal crops, remember that we could still get a lot of winter weather over the next few weeks, so you run the risk of losing it through leaching if it comes cold and wet and plant growth diminishes. So hold your nerve, keep an eye on the conditions, monitor the growth stages carefully and forget about farming by calendar date – because it never worked before and I guarantee that this year will be no exception.


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