Crop Watch: Frit fly damage and disease reported in cereals

The autumn weather has turned wetter in recent days, which has halted field operations in some areas. 

Among the key pests and disease reported this week is frit fly damage in wheat crops along with mildew and brown rust in some of the susceptible wheat and barley varieties.

See also: How two farmers integrate strategic glyphosate in rotations

North

Stephen Bell, Fane Valley (Northern Ireland)

The favourable weather conditions extending through to mid-October has helped crops get off to an excellent start across much of the country.

But recent, wetter weather has left many headlands waterlogged, even though most central field areas remain in decent working condition for the time of year.

Early-sown winter barley crops are now at the three-leaf stage and beginning to tiller, while the bulk of winter wheat has reached the two-leaf stage.

Establishment has been strong, with crops showing robust rooting and good early vigour.

Barley yellow dwarf virus (BYDV) pressure increased in mid-October, although suction trap data shows bird cherry-oat aphid numbers have dropped back in recent weeks.

Even so, mild conditions could still allow aphids present in crops to multiply quickly and spread infection.

Most early drilled, non-tolerant cereals have already had an aphicide spray, often accompanied by foliar manganese to build crop resilience going into winter.

Residual herbicides

Once soils dry up enough to travel, the focus will shift to finishing off autumn residual herbicides, particularly in winter barley, to ensure effective and sustained grassweed control.

Oilseed rape (OSR) continues to perform well, with the most advanced crops at the six-eight leaf stage and green area index values ranging between 1.5 and 2.5.

At present, crops are generally free from phoma and light leaf spot infection, but with mild wet weather forecast disease pressure will increase.

Slug damage is prevalent and still requires close attention, especially in more backward crops on heavier soils.

When conditions permit, attention should turn to propyzamide applications aimed at controlling grassweeds and chickweed, with the option to include a broad-leaved herbicide if required.

With soil temperatures falling this should be planned for the next opportunity when field conditions allow.

With unsettled weather now back, it’s important to protect the solid progress made earlier in the autumn.

Avoiding soil compaction during late fieldwork will help maintain the strong establishment seen in most crops so far.

West

Ben Allard, Pearce Seeds (Dorset, Wiltshire and Somerset)

The recent weather has been what we would expect from a typical autumn for us, wet and mild.

Over the past few weeks, with the change in weather, the number of days suitable for travelling on fields has become more limited.

The heavy land is now out of bounds until spring. Luckily, everything is drilled up, treated with pre-emergence herbicide, and has received its aphicide application.

Assessing my herbicide strategy this autumn, it’s fair to say it has provided some mixed results due to the dry start.

Grassweed control seems to be OK for now; however, lots of small broad-leaved weeds have emerged through the residual barrier, and a top-up of flufenacet/diflufenican has been applied to help nip these out.

Cinmethylin (Luximo) seems to be working well on emerging blackgrass, with it looking sick and under stress.

I just hope that by moving to this earlier drilling window, due to the conditions at the time, it doesn’t come back to bite us later in the spring. Time will tell.

Aphid and gout fly pressure has eased over the past few weeks, with all required applications now completed.

With the recent mild weather, I will continue to watch for aphids in cereals, basing decisions on the aphids present, T-sum model as well as ground conditions to determine whether second applications will be required and whether we will be able to travel on certain soil types.

Hybrid cereals (rye and barley) are looking very good, perhaps a bit too good in some cases, with the need for sheep grazing likely over the winter months.

However, it’s easier to manage a forward strong crop than a poor-looking backwards crop, which we have seen plenty of over the last few years.

Oilseed rape

OSR across the board is looking very good, in fact, some of the best I’ve seen in years.

Prothioconazole has been, or is about to be, applied in response to the rising threat of phoma lesions, which are appearing heavily on crops.

The mild and wet weather provides perfect conditions for this disease, and if pressure continues, a second fungicide application may be needed, as if left unchecked, it can have a severe impact on the crop.

Weed control this autumn has worked really well, with all my Clearfield varieties now treated with Cleravo (imazamox + quinmerac), which has done a particularly good job of keeping charlock under control as well as a range of other broad-leaved weeds.

For the first time in a long while, growers seem more positive about including OSR in the rotation.

I believe this is a result of following two low-pressure flea beetle years, coming off a good yielding year and firmer prices compared to other break crops.

Hopefully, this continues for years to come, as it’s a great break crop which, in the current market, can deliver good margins.

Winter jobs will soon be in full swing as we close the gates on some crops until spring.

These include soil sampling, preparing soil and nutrient plans for sustainable farming incentive agreements and ever-increasing Environment Agency inspections, crop budgeting and planning for the spring ahead, as well as the occasional day of shooting.

East

Harriet Bateman, Prime Agriculture/AICC (w Norfolk, Cambs, south Lincs)

Crops across the board are looking really pleasing compared with recent autumns.

Warm soils through late October have given crops drilled to date a strong start, and the recent rain has been just enough to keep growth ticking along.

Cereals are generally well established and where soils stayed drier for longer, subsequent rainfall has helped even out emergence.

Seed-beds are generally good and pre-emergence herbicides have performed well with moisture arriving in time for most.

Although where bigger herbicide programmes have been used there has been some minor crop effects, but these should be transient.

Residual herbicides are holding, although late-drilled fields will still need watching for blackgrass.

It is worth keeping an eye on manganese levels in cereals, correcting deficiencies now will help crops cope better with the colder months ahead.

As a result of the prolonged mild autumn, mildew and brown rust are visible in some of the susceptible wheat and barley varieties.

Monitor infected crops through the winter; it is unlikely that treatment will be required, and in spring how early intervention is needed will depend on how harsh the winter is.

BYDV risk remains under review. The latest Rothamsted bulletin shows aphid numbers are starting to tail off, but traps from Brooms Barn and nearby sites still report significant local activity.

Later drillings may escape the critical T-Sum threshold (170), but it’s worth recording emergence dates and keeping an eye on aphids until temperatures drop further.

Comparing early November temperatures to last year, it’s been a little warmer overall.

Slugs remain largely under control, but some feeding is showing where trash cover is heavier or seed-beds are cloddy.

Trapping should continue while conditions stay mild; most fields are fine, but there are isolated hotspots of activity.

Bean damage

Bean emergence is even where seed-beds are firm, although rooks are causing damage in places, particularly on lighter land or where the seed-bed is looser.

In oilseed rape, the focus now turns to propyzamide timing. Hold off until soils are around 10C and falling with good moisture levels, and avoid any applications ahead of heavy rain or on saturated ground.

Some early, forward crops are starting to look pale as nitrogen reserves run low, it is unsightly but not concerning, as root systems are strong and new growth remains healthy.

Potato crops have gone into store clean and in good condition. There have been a few isolated cases of pythium, but it is not widespread.

Eye movement is starting a little earlier than usual this year, so it’s worth keeping a close eye on stores, regular checks focusing on temperature and ventilation will help maintain quality through the winter.

Sugar beet lifting continues steadily, but in good conditions and yields are still pleasing. Keep an eye on pest and disease updates via the British Beet Research Organisation bulletins, especially around beet moth and post-harvest cultivation guidance.

As fieldwork is wrapping up on autumn-drilled crops, take the opportunity to assess any total weed control requirements on land destined for spring sowing.

Getting ahead now means a cleaner start in spring. Tidy seed-beds will help manage any green bridge for disease, virus, and slugs.

All in all, it’s been a kind autumn, a few areas to watch, but crops are heading into winter in good order and with plenty of promise for spring.

South

Anna Dunford, Hampshire Arable Systems/AICC (Hampshire)

Blustery winds and showers most days, coupled with the occasional heavy rain has put paid to most field work for now.

The shortlist of outstanding jobs, mainly aphicides and final herbicide top ups are awaiting a weather window. 

Despite the damp weather, most crops are well away and should be past the slug danger zone.

For most farms crop establishment is dramatically better than it has been in recent years, and possibly than it has ever been.

Frit fly damage is presenting itself in a number of crops, and not just those following grass and legume fallows.

Frit fly damage is easy to spot by yellowing leaves and “dead heart” symptoms in which the central shoot dies.

In most cases it is only the odd plant affected, and anyway there is nothing that can be done – a roll and early nitrogen in the spring may help crop tillers.

There is some mildew, net blotch and brown rust in cereal crops, but nothing requiring treatment yet, frosts over winter will help minimise these diseases.

Manganese has been applied in deficient areas which will help to increase resilience against mildew.

Propyzamide applications

Kerb applications on OSR are still a way off, soil temperatures have a little way to go before they hit the target of below 10C and falling.

With the current weather forecast this doesn’t look to be anytime soon. At this stage it is a good idea to be reminded of the straw restrictions following Astrokerb (aminopyralid + propyzamide) applications.

The warm temperatures and damp weather we are experiencing is favourable to disease.

Phoma in OSR has exceeded threshold of 10 to 20% of plants infected in some crops, notably high erucic aciid rape (Hear) and early sowings.

These are being treated with prothioconazole, which will add light leaf spot protection. 

Pleasingly we are finding very low numbers of cabbage stem flea beetle (CSFB) larvae, but there are still some adults in the crop which will still be breeding while the weather remains warm.

The low number of CSFB adults may be down to the large number of growers cultivating rape stubbles post-harvest but also must be helped by the decreased area grown for harvest 2025.

Furthermore, unlike last year we haven’t found any signs of cabbage root fly in crops despite early sowings.

Winter bean drilling is generally complete, with some crops up at two-leaf. Pre-emergence herbicides appear to be working well.