In Field Focus Issue 17

ISSUE 17 • Summer/Autumn 2024

RESPONDING TO EARLY DRILLING RISKS With early wheat drilling potentially on the cards for many growers this autumn, after last autumn’s difficulties, what can be done to mitigate the risks?

There is little doubt many growers will be keen to get wheat crops in the ground early this autumn, says ProCam technical manager for the South and West of England, Paul Gruber (pictured).

And while this is understandable after the bitter experiences of last autumn and winter, it does undoubtedly bring risks, so being prepared is crucial, he stresses.

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IN THIS ISSUE: OSR options

Beating blight

Restoring grassland

Responding to early drilling risks

Earlier drilling increases pressures from many grass weeds, says Paul Gruber who advises killing off at least one flush of blackgrass in stale seedbeds before drilling. He says brome problems are also on the rise

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Grass weed growth “Drilling earlier increases the pressure from pretty much all grass weeds,” says Paul Gruber.

“Remember, we’re coming off the back of a season with high grass weeds burdens in cereals and break crops because residual herbicides were late going on or simply weren’t applied because of the washout winter. So seed carryover is set to be high.

“Don’t rely only on herbicides.

I always advise killing off at least one flush of blackgrass in stale seedbeds before drilling. If we have low dormancy in blackgrass seed this summer, it will be disastrous in fields drilled too early because huge numbers of seeds will germinate thick and fast in-crop without a pre drill glyphosate kill.

“High grass weed pressures clearly increase the need to bolster herbicide strategies – for example beginning with a residual preemergence followed by a combined residual plus contact treatment applied at peri-emergence.

“Many areas are also seeing increased brome problems. Non inversion tillage favours brome, so if you’ve had brome seed shed you need to plough it down, especially where a second straw crop is following. Ploughing will also help to destroy green bridges that carry other weed, pest and disease problems,” Paul adds.

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Disease decisions As well as grass weeds, pressures from disease, pests and lodging also increase with earlier drilling, says ProCam technical manager for South and East England, Justin Smith.

but there is the added complication of take-all, particularly if drilling into stubble.

“Using Latitude on true second wheat is obvious, but don’t forget spring wheat and spring barley are also take-all hosts, and there’ll be plenty of winter wheat following spring barley this autumn.

“Also, remember that foliar disease resistance ratings of varieties are typically determined from October drilling. But we see massively more Septoria in September-drilled wheat than in October-drilled crops.”

While earlier drilling, in theory, reduces yellow rust risk, Justin says a mild winter will encourage any yellow rust to build up. “Although normally a later season disease, we saw plenty of early brown rust in Crusoe this season because of this effect,” he points out.

“Eyespot risk is also increased in second wheat drilled early, and in first wheat after maize. Some varieties have the Rendezvous gene which increases resistance, so take advice.

“Early drilling also increases barley yellow dwarf virus (BYDV) risks massively. This increases the need for timely aphicides, but also make sure you destroy green bridges and consider varieties with BYDV tolerance or resistance – especially further south.

“Gout fly risk also increases with early drilling, so be extra careful if you have a history of gout fly or lots of grass weeds, as these carry gout fly and there’s no chemical control.”

Variety viewpoint It’s understandable if growers want to get crops in the ground earlier after last autumn, says Justin Smith, but be aware of all risks

“If you’re not prepared to invest extra effort, earlier drilling isn’t for you,” he warns. “It’s for people prepared to invest effort who are pushing for yield.”

With second wheats, especially, Justin urges leaving drilling as late as possible. Weed, pest and foliar disease burdens are likely to be higher in second wheat, he says,

Northern England tends to drill winter wheat earlier than the South anyway, says Yorkshire-based agronomist, Scott Colclough, but whenever winter wheat is drilled early, correct variety choice is crucial.

“As well as high yield, you want varieties that are slower developing, stiff strawed and with good disease resistance. Examples for the early slot include Parkin, Graham, Bairstow, Palladium and newcomer Arnie. Typhoon is another one to consider,” he adds.

“Seed rates will also need reducing compared with drilling later, but check what’s appropriate

Among other characteristics, you want varieties with good Septoria resistance if drilling early, says agronomist, Scott Colclough

for each variety, location and the conditions. You don’t want crops sown too thickly. But if you’ve got grass weed problems, sowing too thinly reduces crop competition.

“Another thing to consider is seed availability. Wheat seed growers had the same issues as everyone else last autumn, with difficulties establishing crops. So there simply isn’t going to be the normal level of seed availability and choice, and this will be compounded if we have a delayed harvest.

“Therefore, make sure you have your chosen varieties secured, or home-saving might be wise. If home saving from this harvest, have a reliable seed cleaner lined up. They’ll be in demand. Alternatively, many growers have wheat seed left over from last winter. If using over-yeared seed, have it tested – not just for germination but also vigour.”

Also important to consider, says Scott, is that drilling while ground temperatures remain warm will shorten residual herbicide persistence, as they are degraded faster in the soil. “If soils are dry, it will also reduce residual herbicide uptake. Avoid drilling in dry seedbeds,” he says.

Lodging lessons Underestimate the risks of early drilling and it could have short and long-term consequences, says Lancashire/Cheshire-based ProCam agronomist, Kathryn Richards, not least increased lodging, which will not show up until next summer.

“Choosing stiffer-strawed varieties is key,” says Kathryn. “But so too is correct seed rate. Earlier drilled crops are in the ground for

longer so tend to grow taller, and too high a seed rate which creates densely-packed tillers increases this.

There’s a lot of KWS Extase grown around here, which can get quite leggy if drilled early.

wheat drilled in September and the 30-40% that ended up being drilled in October in the area last year, growers are 100% going to want to avoid October drilling.

While September-sown wheat managed to get its roots down before the persistent rains arrived, going on to produce good-looking crops, wheat drilled even in the first week of October suffered from poor rooting and backward growth, she says, while it sat in pools of water for six months.

“Although it was possible to nurture these stressed crops through the spring, they had to be handled with kid gloves,” says Eilish.

“For example, they were harder to manage with PGRs. That said, we’d urge against drilling too early, and certainly not in August because crops will end up covered in disease

Stiffer-strawed varieties and correct seed rates are key starting points for managing the increased lodging risks that come with earlier drilling, says Kathryn Richards

“We also have fertile soils from mixed farms in the area, so crops tend to tiller more anyway. Plus, thick crops get more disease and we get a lot of wind blow which causes damage as tillers rub together.

Thicker crops don’t seem to yield as well as those drilled slightly thinner.

“With winter cereal drilling anywhere from 30-80% down last autumn because of the rain, I understand growers will want to get crops in the ground early, but I don’t like to see wheat planted before 15 September.”

Scottish situation Highlands and Morayshire ProCam agronomist, Eilish Johnston, says after seeing the difference between

Growers are definitely going to want to avoid the risk of delayed drilling, says Eilish Johnston, but it is important not to drill too early

and be at greatly increased risk of BYDV and lodging.

“Even drilling in the third or fourth week of September increases Septoria risk. Every year we seem to be getting wetter periods that favour Septoria. Choosing a more resistant variety gives an extra layer of protection. Our biggest winter wheat is Skyscraper for distilling. But Blackstone looks a good new potential variety. Keep an eye on how it looks at harvest and, of course, it will need to be accepted by the local distiller.”

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Fighting back against flea beetle in oilseed rape With no magic bullet against cabbage stem flea beetle, could adjusting drilling date and planting a companion crop put you in a better position?

Companion crops can aid oilseed rape establishment by protecting against flea beetle, improving soil condition and reducing weed pressure

We need to think differently about how cabbage stem flea beetle (CSFB) is managed, says ProCam regional technical manager, Nigel Scott.

CSFB problems can arise whenever winter oilseed rape (WOSR) is planted, he says, but in parts of the country problems seem worse when drilled during its traditional mid to late-August window. This seems to provide a perfect storm for adult beetle invasion and crop failure, he believes.

“If this is the case, depending on individual farm situations, one strategy is to consider planting WOSR much earlier, at the very start

New for this year, we are marketing the companion crop GreenPack Bronze containing buckwheat and fenugreek, says Nigel Scott

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of August, or to miss out August completely and plant well into September.

“In both scenarios, varieties need choosing accordingly. Hybrids make sense because you want good establishment from early vigour.

But if drilling earlier, you don’t want the crop to get too far ahead over winter, because it will be prone to later frosts.

“Traditionally, varieties have been bred for late-August drilling. So a changed approach means looking at variety choice in a different way – selecting varieties that sit at either end of the spectrum. These might not be on the Recommended List, but have a specific purpose,” he adds.

LG Areti

Earlier drilling By drilling earlier, Nigel says the aim is to get WOSR to 4-5 leaves before adult beetle migration occurs so it can tolerate adult feeding. Larvae are difficult to avoid in this situation, but if a vigorous plant with a thick stem can be created, he says the crop has a fighting chance.

“I’ve seen crops drilled in the first week of August or into July develop a big collar at the base of the plant.

This makes them better able to withstand infestation.

“A variety we’ve seen that’s particularly suited to early drilling is LG Areti. It grows away well initially but has a prostrate growth habit close to the soil over winter. So it’s potentially less at risk from frosts while also providing good ground cover.

“Most critical in terms of CSFB is its spring vigour. It’s very quick to move in spring, meaning it can grow away from larval feeding nice and rapidly.”

Later drilling

RGT Blackmoon

Alternatively, by planting later, for example well into September depending on location and conditions, Nigel says the aim is to plant after adult CSFB migration has finished.

“In September, there should also hopefully be better soil moisture to help establishment and soils should be reasonably warm. However, at this stage, you want a rapidly-establishing plant to compensate for later drilling.

You need to grow the most vigorous variety you can.”

Nigel’s recommendation here is RGT Blackmoon. “Its vigour in trials has been outstanding, and field performance is equally impressive.

I’ve seen Blackmoon drilled in mid-September race away. Drilled alongside an alternative hybrid, it was chalk and cheese, and the vigour was ultimately the difference between survival and failure. Drilling in September is a useful tool for avoiding beetle, but variety choice is essential.”

Companion cropping In tandem with drilling date and variety, Nigel has had good results with companion cropping to reduce CSFB damage when drilled into stubble.

“A companion crop is a nobrainer for SFI payments anyway.

But companion species choice and variety choice are critical if we’re to use them to support our CSFB

strategy as well as access the £55/ha payment.

“New for this year, we’re marketing GreenPack Bronze. This companion crop mix contains tartaric buckwheat, which is a ‘must have’ to help shield WOSR from beetles. But it also contains fenugreek, which has a garlic odour to act as a CSFB deterrent.”

Tartaric buckwheat has been selected as a particularly vigorous variety, with a seed size that means GreenPack Bronze can be mixed with the OSR and established together.

Alternatively it can be established ahead, with the OSR drilled into the protective canopy. Flexibility is key, and the vigour of the companion crop means it is able to provide an IPM tool in either instance as the buckwheat grows ahead of the rape to provide a shield.

“Clearly, companion crops and OSR need moisture irrespective of drilling date,” Nigel emphasises,

“so a stacked approach is needed.

Moisture, companions, variety choice and drilling date all need to work together to maximise the chance of success.”

Steps to consider to mitigate CSFB risk • Plant early or late – to avoid peak adult beetle migration • Choose a variety that aligns to your planned drilling date – drilling early requires spring vigour, drilling late demands autumn vigour • Plant a dual-purpose companion crop – providing a shield and deterrent against CSFB • Plant when adequate soil moisture for rapid OSR and companion crop establishment

Maintaining effective blight control requires clarity of thought Potato growers will need to develop alternative protection strategies to control blight in 2025 and beyond. But recent regulatory changes and disease resistance mean this might not be straightforward.

Mancozeb has been the mainstay multi-site fungicide active ingredient for the control of potato blight, but its approval expired on 31st May 2024. As a result, the final date for the sale and supply of all products containing mancozeb will be 31st November 2024, with the final storage, disposal and use-up period ending on 31st November 2025.

Potato growers will therefore need to modify their blight protection programmes accordingly.

And, although alternative active ingredients are available, the rules and regulations surrounding their use and application intervals aren’t entirely straightforward and are further complicated by confirmed cases of resistance to some key actives on the continent.

“For example, instead of being able to apply three consecutive applications of CAA (carboxylic acid amide) fungicides, the latest

FRAC (Fungicide Resistance Action Committee) guidance is that these should now be limited to a maximum of two consecutive applications,” explains ProCam agronomist, Harry James.

“That’s a sensible recommendation based on the loss of efficacy of this group of fungicides on the continent, with crop protection manufacturers such as Syngenta going a step further by advocating the use of mandipropamid in alternation with fungicides with a different mode of action.”

Resistance to oxathapiprolin (Zorvec) has also been confirmed in some parts of northern continental Europe including the Netherlands, Belgium and Germany, with the postZorvec application interval being reduced from 10 days to 7 as a result.

It must also be used in alternation with a non-CAA chemistry.

“This will make it more labour intensive and time consuming to keep crops clean,” Mr James describes, “especially as this key active no longer provides a curative effect. Instead, it can only be relied on to deliver preventative activity which means sprays will need to be applied on time every time in order for crops to remain protected.

“To avoid any confusion that the new rules might introduce, and to ensure they don’t fall foul to the same resistance woes that their European counterparts are already dealing with, UK potato growers should seek professional advice from their agronomist to help them devise a suitable blight programme for this season and beyond,” Mr James advises.

Growers should also be aware that although fungicide resistance hasn’t yet been confirmed in UK crops, the risk remains high and is further escalated by the shortfall in British seed potatoes which means there’s a risk of resistant strains being introduced by imported seed stock.

“The high incidence of foliar and tuber blight in continental seed

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crops means there’s a very real risk of resistance affecting British crops,” Mr James continues. “For that reason, anti-resistance strategies – alternating modes of action and limiting the exposure of any single active – must be followed from the outset.

“Keeping a close eye on resistance updates throughout the season will be essential, as will taking professional advice to devise a suitable spray programme, not least because the ever-changing legislative position and evolving resistance situation will make keeping abreast of the latest rules that much more complex.

“But, with careful planning, growers and their agronomists should still be able to achieve good levels of blight control and to stay ahead of the threat of resistance.

It must be stressed however that the key to reliable control will be to adapt programmes according to weather conditions and to use forecasting tools to determine when the threat of blight is at its highest.

Cultural controls, such as selecting varieties with better natural blight resistance, and taking extra care to remove volunteer potatoes from dumps and other crops in the rotation should also be factored into the equation.

“Nothing, however, will beat getting into the field and putting boots on the ground to assess the crop, the severity of disease pressure and if a blight infection has occurred,” Mr James concludes.

Potato crop displaying typical foliar blight symptoms

Harry James warns of blight resistance affecting British potato crops this season

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Reseeding after a wet start Restoring grassland after a wet start requires extra care.

The prolonged wet weather has left some grassland reseeding unfinished. Rhys Owen discusses how to restore remaining swards in line with the Sustainable Farming Incentive in England and the Growing For The Environment scheme in Wales.

Reseeding advice Many farms have entered one or more SFI or GTFE scheme, with grass, legumes, herbal leys, red clover, lucerne or undersown cereals proving popular. Before being sown, damaged soils must be repaired, with consideration given to weed control where chemical options aren’t allowed.

Ideally, reseed after a brassica or cereal as these provide an opportunity to control weeds, improve soil structure and disrupt pests like leatherjackets. Where a break crop isn’t feasible, use alternative controls like grazing to combat perennial weeds, or glyphosate for a completely clean start.

Test soils before reseeding: treat acidic soils with lime to pH 6.5.

Target a phosphate index of 2, and 2- for potash.

If reseeding in summer, be aware that dry conditions can hinder establishment as weeds can dominate.

Drill grasses and clover at 1015mm into a firm seedbed rolled at an angle to close drill slots for better seed-soil contact.

Clovers and herbal leys must be well established before winter:

August seeding is preferable as establishment suffers when drilled later. Light grazing before winter promotes tillering, reduces weeds, and allows light through the grass canopy. Grazing can start when grasses and clovers pass the pull test, but chicory and plantain should have at least six leaves.

Some multi-species swards can’t be treated with an herbicide, but grass and clover can: spray 4-6 weeks after emergence with a clover-safe herbicide. Triad (tribenuron) controls perennial weeds in red and white clover, or Squire Ultra (amidosulfuron) can be used on white clover.

Clover plants must have one trifoliate leaf before herbicides are applied, but don’t allow weeds to become too strong. Spray docks when no larger than two true leaves and follow the recommended postapplication grazing interval.

Direct drilling is preferential to broadcast seeding, especially when using a close-space drill. Be aware tined seeders can stimulate weed germination and need enough moisture to be present.

Tetraploid grasses having a larger, more vigorous seed, but don’t discount the ground covering benefits of diploid perennials.

Don’t apply nitrogen until overseeded plants have established as this encourages competition from existing plants. Likewise, don’t close overseeded fields for a silage cut. Instead, graze briefly with high stock numbers, but don’t overgraze as sheep will select young seedlings. Give herbs more time to develop a root system, and leave to rest over winter.

Over-seeding guidelines Beyond spring, the best time to overseed is when grass growth slows after grazing or silaging.

Use an aerator or sub-soiler to repair compaction, or, if lots of levelling is needed, do a full reseed.

Clover-safe herbicides for docks and thistles are limited in established grassland, so use a non-clover safe option and reintroduce clover later.

Cropping restrictions must be followed. For example, clover can’t be sown within six weeks of using Doxstar Pro. With Forefront-T, four months must pass before clover is drilled.

Rhys Owen offers his grassland restoration advice

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