It is estimated around 75 per cent of sugar beet seed will be treated with the Cruiser SB (thiamexotham) seed treatment granted emergency authorisation this season.
Strict conditions of the have been imposed by Defra, including a ban on any flowering crop being planted in the same field within 32 months of a treated sugar beet crop.
With both field beans and oilseed rape in the rotation, Suffolk grower Will Hitchcock opted for the Cruiser SB seed dressing on just a small proportion of seed destined for land capable of holding a second and third cereal.
He says: 鈥淢aintaining our current diverse rotation is more important to us than the potential benefits that Cruiser may bring to the beet crop. As such I feel the emergency approval is not totally beneficial and in some respects is not sustainable in terms of maintaining a balanced rotation. The emergency approval details are too restrictive.鈥�
Mr Hitchcock has concerns that the lack of cold winter weather has not checked aphid populations or frosted overwintered land going in to beet, meaning seed bed quality and therefore establishment may be compromised.
鈥淩apid establishment of the seedlings is key to beating aphid migration. Our experience from two seasons ago is to be patient. Land that we could not get a suitable seedbed on in April was left until rain in the first week of May before it was drilled. This very late drilled crop emerged very evenly in the right conditions and suffered from near zero levels of virus because it missed the aphid migration.鈥�
Untreated
Cambridgeshire arable farmer, Hannah Darby is leaving all of her seed untreated this season.
鈥淓ighty per cent of the reason is our rotation. Peas are important to us and the derogation means that you cannot grow a flowering crop in the following years after the sugar beet crop. We have had to diversify our cropping away from sugar beet due to the problems in the past and that is why peas and other flowering crops have become more important in the rotation.Sugar beet is not the important crop to us it once was and we are only growing 17 hectares in the last year of our contract.
鈥淎lso, because we did not have to wait for the results of the derogation [announced on March 1] our seed is now in the shed and able to be drilled when we like. Another factor was that we are trying to avoid the use of insecticides.鈥�
Forecast
According to BBRO, the date of first arrival of aphids in crops in 2022 is forecasted from April 19 onwards, in comparison to 2021, where the aphid flight date was May 18.
In 2020 when the crop was decimated by virus yellows, the forecasted incidence of virus yellows was 85 per cent with an expected aphid flight date of March 24.
All sugar beet growers must adhere to the robust stewardship programme that has been agreed by the Health & Safety Executive which also includes restrictions on seed rates and targeted use of herbicides.
The rate of the active ingredient authorised is also lower at 45g/unit of seed which is equal to 75 per cent of the concentration used up until it was banned. This will give growers up to 10 weeks of protection against virus carrying aphids, protecting the crop in the early stages when it is at its most vulnerable.
Additional
Depending on aphid numbers in late April, May and early June, Cruiser SB treated crop may require additional foliar insecticides, if the thresholds are exceeded. BBRO recommends to start monitoring crops for aphids from eight weeks after drilling.
In Cruiser SB treated crops, foliar insecticides must be applied in the sequence T1 flonicamid (as either Teppeki or Afinto), followed by T2 Insyst (acetamiprid). In non-Cruiser SB treated crops the same options are available but there is no restriction in the sequence of use. An EA for a third option for a foliar application is being progressed, says BBRO.
