Crop Watch: Cold spell to reset disease and insect pressure

Conditions have turned much wetter after storm Claudia late last week, leaving many fields too wet to travel on.

Fortunately, crops have established well and are in a much better situation than this time last year.

The colder spell this week has been welcomed, as it will help ease the disease and pest pressure resulting from the mild autumn.

See also: How next-gen satellites take guesswork out of N management

South

Oli Pilbeam, CCC and CLM  (Kent and Sussex)

There’s an old saying that “a crop well sown is a crop half grown” – and we’re hoping this is the case this year. 

It was a great drilling season and has been a kind autumn so it’s lovely to see well-established green fields in November, as well as machinery washed off, parked up and relatively empty yards as arable teams get some well-deserved rest.

What will the resident mice now eat with no leftover seed in the sheds for the first time in many years?

We’ve managed to get top-up blackgrass herbicides on wheat in good time, mainly flufenacet-based actives, and I’ve tried the new Fundatis (beflubutamid + bixlozone) on the problem ryegrass fields – so far to great effect.

It’s still mild for November, which is worrying in terms of barley yellow dwarf virus (BYDV).

As I write, we’ve sprayed for aphids once, but we may have to do it again unless there’s a significant temperature drop.

Wheat and oilseed rape are leaping through growth stages. We soon will be addressing the phoma now appearing, along with a propyzamide application when soil temperature drops aiding with blackgrass control.

Next spring

We’re a long way from harvest so aren’t counting any chickens, but it’s the first time in four years we’ve had crops come up in such good order.

This will make for delicate judgements next spring because, although they have strong yield potential, there’ll also be higher disease and weed pressure, with mildew and brown rust already visible. 

Given this crop potential – and the fact that bank accounts are depleted – there is an argument to push crops.

But as ever, we need to keep an eye on crop prices as we quickly could be spending 4t/ha-worth of wheat on inputs alone, leaving little margin to cover all the other costs. 

Right now, we could do with some frosts to reset the disease and insect pressure.

Basically, we want a “normal” winter – although I’m questioning what that is and what it used to look like. Sledging weather, I suppose.

As the agronomy quietens over winter, my consultancy “arm” increases – helping clients with budgets, cashflow planning, tenders and adapting contract farming agreements. 

A lot of contract farming agreements currently in place aren’t fit for purpose as we move away from subsidy support, leaving the divisible surplus “pot” smaller, so there will be a lot of renegotiations.

I see more land coming available in the short term and, given how tight margins are, a shift to farm business tenancies for more risk-adverse landlords.

East

Ryan Baker, Frontier (Suffolk/Norfolk) 

The weather has started to change in the last week. With significant rain last Friday and lower temperatures this week, both growth and pest activity have started to slow.

However, prior to this, winter cereals were growing at an almost concerning rate. Both aphids and frit fly were easy to find.

This has unfortunately resulted in several early drilled barley and wheat crops reaching the T Sum 170 threshold for the second time; not something that has occurred very often in my career so far.

Top up herbicides have been very effective this year where application occurred close to one of the, admittedly rare, rain events.

High population blackgrass fields can fortunately be counted on one hand.

Flufenacet has worked well when topping up after cinmethylin. Beflubutamid + bixlozone have proved their place on higher populations of both grassweeds and broad-leaved weeds.

The characteristic red colouring of weeds after application is very visual.

Mildew

The warm weather has also encouraged mildew in oilseed rape and wheat, as well as in barley.

Prothioconazole and difenoconazole have been utilised in oilseed rape to protect against any phoma infection.

In winter cereals, treating mildew in the autumn is rarely economical; prothioconazole and proquinazid can be used protectively in severe cases.

Cyflufenamid is a true eradicant, but can only be used in the spring. As with many issues occurring now, a frost would be the best solution.

Beans have established well this year. Whether ploughed in or drilled, emergence has been even and are not too advanced for the time of year.

Sugar beet yields have been very respectable. Up to this point, sugars have remained high and dirt tares relatively low.

The rain in the last week is likely to change this slightly. Conditions have allowed wheat to still be established after sugar beet rather than leaving for spring barley.

Caution has been taken on whether to apply residual chemistry pre-emergence, or whether to wait for the crop to emerge. 

Now the weather has started to alter, thoughts are turning to propyzamide in oilseed rape. Conditions are still too warm and dry, but Corteva’s app gives a good map based early warning for when appropriate conditions occur.

As the canopy starts to decline, decisions can be taken on whether straight propyzamide is appropriate or whether the addition of aminopyralid or Arylex (halauxifen) and picloram would be more suitable.

West

Dominic Edmond, Matford Arable (Devon/Cornwall)

In the last month, we have experienced more typical autumnal weather. As it stands, November is now the wettest month of the year, and we’ve had 150mm of rain since my last report.

Consequently, field operations have been few and far between, however the pleasing thing is nearly all crops have been drilled and are well established.

A few crops that were drilled in September, are looking very well established, and a colder period of weather would be welcome for most of those.

With ground conditions tricky, I’m glad I persevered in getting pre-emergence herbicides on, particularly on barley.

Although conditions were dry, with a relatively dry outlook, the pre-ems have worked well with plenty of moisture about in the last month reactivating them.

Where picolinifen herbicides have been used there has been some transient bleaching, but nearly all are growing away from that now, and where Alternator Met (flufenacet + diflufenican +  metribuzin) has been used there appears to be decent control of groundsel, so far.

Second BYDV spray

The only frustration with the recent rainfall has been the inability to apply aphicides for BYDV.

Numbers of bird cherry-oat aphid at Starcross peaked at just under 1,300 during the second week of October and numbers have declined significantly since then.

A lot of crops managed to receive one aphicide, but it’s been a struggle to get the second one on, which over the past few years has proven its worth.

This week brings cooler drier conditions so, hopefully, that reduces the pressure somewhat while it may present an opportunity to travel.

The other reason there will be a need to travel will be to clean up some of the many acres of grass seed that was established this autumn.

Many are very weedy and need treatment, but ground conditions are soft, and it will have to be a game of patience before attempting to get them sprayed.

As we head into the winter months, it’s the first autumn for at least three years, where crops have been drilled into good conditions, with weather that has been kind post drilling.

So, with crops well established, it at least gives us a fighting chance of having crops looking as they should do next spring.

North

Greg Dawson, Scottish Agronomy (East Scotland)

The arrival of colder weather, including some sporadic snow flurries, has applied a much-needed brake to both crop development and the progression of weeds, pests and diseases.

Mild temperatures and early drilling have resulted in plenty of forward cereal crops which, in some cases, are displaying symptoms of manganese or nitrogen deficiency.

Many crops have received an application of manganese, but with most of the Scottish arable area falling within nitrate vulnerable zones (NVZs) and an expectation that winter weather would soon slow demand, there was little else that could have been done to support crops which exhausted the soil nitrogen supply.

The benefit of mixed farming systems in increasing soil nitrogen supply has been apparent this autumn.

It was also visible in the very dry conditions earlier in the year. As soon as conditions and NVZ restrictions allow, early spring N applications will be important to support tiller numbers particularly on early developing crop types such as winter barley and rye.

Yellow rust

Significantly colder temperatures than those experienced to date are needed to eradicate the yellow rust inoculum that is present in many wheat crops.

Cooler weather will slow the rate of development, but the expectation is that T0 treatments will be hugely important in 2026.

Conversely to the focus on the challenges facing early drilled crops, there is also a significant area of wheat drilled in late October and into November following later harvested crops of vegetables or potatoes and in some cases, as second cereals.

This is partly down to growers seizing the opportunity of good ground conditions, but is mostly in response to the depressed state of the malting spring barley market which accounts for a significant proportion of Scottish cereal production.

The news from this sector continues to indicate a downturn in demand for grain and growers who can are choosing alternatives. 

It is far from new advice, but understanding the cost of production and the relative yield performance of alternative crops through local trials or shared grower experience are essential components of making these decisions in difficult times.