Replacing neonicotinoid seed treatments is going to be a significant challenge over the coming years, and unfortunately there is no silver bullet to succeed them. Focusing on wheat and barley, here are some options to consider for Barley Yellow Dwarf Virus (BYDV) and slug management strategies to prepare for a post-neonic era.
Delaying the sowing of cereals can minimise BYDV infection, as in most years this will reduce crop exposure to the aphid colonisation period.
The success of this system will depend on seasonal conditions - particularly temperature (see monitoring below). Drilling later may also be an attractive option for those already looking to this strategy as part of their black-grass management, and could potentially also help reduce disease pressure, such as Septoria in wheat.
However, in areas that have historically struggled with slugs, delayed drilling will be a less appropriate strategy. Drilling later can result in greater moisture within the soil and difficulty constructing a fine and consolidated seed bed, creating a favourable environment for slugs.
It is not unheard of for aphids to still be flying in mid-December if conditions are mild, so it is vital to utilise the data from the AHDB’s alerts service or other similar services to understand the number of aphids flying in your region. In addition, try to keep a record of the temperature throughout winter and remember that although aphids can’t survive below -7°C, it will be warmer within the leaf sheathes.
Data from our OSR: The Big Picture report found that after the ban on neonicotinoids autumn insecticide use increased, and it is likely that the treatment of cereals crops will follow suit after a neonicotinoid ban.
However with aphid resistance to pyrethroids identified in the field it is vital to not over rely on this approach, and only treat where necessary. If a pyrethroid spray such as decis is required, then in a post-neonic era prompt pyrethroid timing is even more important, as well as following the AHDB’s advice to use the full recommended dosage, in order to manage resistance levels in the field.
An AHDB Information sheet on slugs suggests that direct drilling can increase the likelihood of a slug problem, and while ploughing is a good option, even min till shows a decrease in slugs compared to direct drilling (Source: AHDB Integrated slug control)
No matter what your establishment technique, it is clear that open, damp and cloddy seedbeds provide free slug movement and shelter. So ideally, your cultivations should create a firm consolidated seedbed, with good seed-to-soil contact.
Slug pellets are an obvious alternative to neonicotinoid seed treatments, albeit the seed treatments were primarily used to deter grain hollowing, and the pellets tend to be for protecting emerging seedlings. In the past those with higher slug pressures may have used both in a control programme.
As with insecticides for BYDV, it isn’t an ideal scenario to increase the number of slug pellets you are using as a direct replacement for neonicotinoid seed treatments.
However for those that do need to use pellets to counter slugs, remember that the guidelines for metaldehyde pellets have changed recently to help increase protection of birds and small mammals that tend to feed and breed in hedgerows. The guidelines now restrict any use of metaldehyde pellets within a minimum of 10 metres of any field boundary or watercourse.
All of this information is underpinned by conducting small scale trials as soon as possible to understand what works for you on your farm. This could be strip plots to understand the impact of seed rates, varying cultivation techniques, or a trial into the impact of delayed drilling on your crop.
Remember when you are designing trials not to be too ambitious. It is important to be clear on the question you are trying to answer, and how you are going to answer that question, given the tools and machinery available to you.
In the future, it is hoped there will be other alternative options available in the market to support you in your management of BYDV and slugs. For example, research into BYDV-tolerant or even resistant varieties is ongoing, with KWS ready to launch a BYDV tolerant winter barley feed variety. Varietal traits are obviously an attractive option, but further research to illustrate the strength of this trait in the UK is ongoing.
After much wrangling, neonicotinoids seem set to become the first pesticide to be banned without ever failing a regulatory test.