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Agricultural Policy

Farming without neonicotinoid seed treatments

Cereal crops are likely to be more at risk from early slug damage and aphid-borne barley yellow dwarf virus (BYDV) in future, following the EU Member States endorsing a proposal to restrict neonicotinoid seed treatment use to greenhouses only.

Key takeaways

  • Neonicotinoid ban likely to increase slug and aphid risk
  • More reliance on cultural controls, which will need to be integrated with remaining chemical options
  • Support rapid establishment with variety choice and early nutrition
  • Monitor crops closely to assess pest risk and need for control

The EU decision means UK growers only have one more autumn to use products such as Redigo Deter (prothioconazole + clothianidin) to protect cereal crops.

“Attention is now turning to how growers are going to farm without these seed treatments,” says Claire Matthewman, Bayer’s Campaign Manager for Seed Treatments.

While BYDV tends to be more prevalent in milder regions further south in the UK, almost any area can be at risk in milder autumn or winter weather.

Equally, slugs are almost an ever-present threat across the UK given the right conditions, but especially so in wetter regions.

 

Cultural controls

The loss of neonicotinoids means cultural controls will become an even more important part of integrated pest management in the future.

For slug control, there are several options. These include:

  • Ploughing to bury surface trash, which will considerably reduce slug populations
  • Using minimum tillage, which reduces slug populations more than direct drilling
  • Drilling at 4 cm deep to help to deny slugs access to seeds before emergence
  • Rolling after drilling to reduce slug activity by making it harder for them to move around
  • Using a stubble rake to disturb crop debris that slugs live among and feed on
  • Introducing beetle banks to provide a habitat for carabid beetles, which feed on slugs

 

It is not yet clear how the withdrawal of neonicotinoid seed treatments will affect cereal yields, but most farmers expect they will have to change some farming practices as a result.

“We used neonicotinoid seed treatments primarily for slugs, but also for aphid control,” says David Fuller, Arable Manager of McGregor Farms in the Scottish Borders. “I think the ban is bad news – 60% of the wheat we grow is treated with Redigo Deter.”

All wheat that follows oilseed rape and vining peas is treated with Redigo Deter. Slugs are the main challenge after oilseed rape, whereas aphids are the focus in wheat after vining peas. “There is no silver bullet,” he says.

Mr Fuller is planning a number of cultural controls to reduce slug pressure once neonicotinoid seed treatments have been withdrawn, including:

  • Using a straw rake after harvest to destroy slug eggs and habitats
  • Continuing to bait, as well as using other remaining treatments for slugs within EU regulations, such as pellets
  • Doing an extra cultivation – using a Simba press – after oilseed rape has been harvested in high-pressure circumstances

 

Crops will continue to be monitored for aphids, which Mr Fuller always has done, and sprayed in October or November, if necessary. “The tools are disappearing rapidly, which puts further pressure on those remaining.”

Late drilling – another potential method of minimising opportunities for pests to infest crops – is not possible in the Scottish Borders, as weather tends not to be suitable from mid-October onwards. However, colder autumn weather does mean aphids are less mobile, which reduces crop damage.

“Thankfully we aren’t handcuffed by black-grass, so we can drill early,” says Mr Fuller. “What was good about Redigo Deter was that it was systemic, so it would protect the crop as it developed, but insecticides only protect what’s there and have limited persistency.

“Establishment is such a challenging time for the crop and Redigo Deter was an integral support mechanism during that time. Damage to the crop during establishment will hamper its progress throughout the season, undoubtedly resulting in crop loss. How bad that loss will be remains to be seen.”

 

Disorientating slugs

Gordon Rennie is a grower and agronomist based in the south of Scotland who believes growers will need to use additional cultural controls and be more selective about the varieties grown in future. Fast emergence and establishment are key to mitigating early pest damage, he says. And seed vigour also plays its part.

“Make sure you’ve got high-vigour seed – and consider sowing a hybrid winter barley variety for even more vigour.

“You want crops through the ground as quickly as possible, so you must combine drill fertiliser with the seed. Placing nitrogen and phosphate beside the seed is the only way to go. If you don’t want slugs, you must have a minimum soil disturbance system.

“If you think you’ve got a slug problem, plough your field one day before you sow. When you invert the soil, it takes at least seven days for the slugs to work out why they’re upside down.”

For aphids, Mr Rennie says insecticides are the only solution in some circumstances, but advises they should always be complemented by other pest management measures.

“If you have to use an insecticide in the autumn, always use a product from one of the R&D companies, like Bayer. Insecticides must be used judiciously, as part of an integrated pest management system. It’s crucial to properly assess the crop before you buy the insecticide.”

He also believes some methods used for decades to control pests and maximise yields are still very effective.

“We have to go back to more rotations or ploughing. Aphids live on scrub and debris around the edge of the field, so don’t provide a habitat for them – plough that in. If you cannot plough, it is essential to use glyphosate way ahead of sowing to deny slugs and aphids a favourable habitat. And rolling to consolidate seedbeds is yet another method of cultural control.”

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Top tips for aphid control

Here are 5 key things to consider when it comes to aphid control:

  • The loss of neonicotinoids will put greater reliance on pyrethroids, but avoid over-reliance due to resistance concerns
  • Utilise aphid monitoring tools and T-sum calculations to assess aphid risk accurately and help optimise spray timing where necessary
  • Use full recommended rates where insecticides are applied
  • Minimise the “green bridge” that volunteers or weeds provide for aphids between crops
  • Consider drilling later where possible, and/or increasing seed rates

 

Adam Tidswell, Bayer’s Commercial Technical Manager for Yorkshire, says:

“It’s a case of going back to how we farmed before neonicotinoid seed treatments, back in 1991. That means going back to monitoring for aphids and cultural controls to keep slugs at bay.

“In terms of chemistry, growers should be mindful of buffer zones and how they will impact protecting the headlands. Stewardship will be paramount to protect the foliar pyrethroids and slug pellets currently available.”