This adds an application of InSyst to the two of Biscaya (thiacloprid) and one of Teppeki (flonicamid) in growers’ armoury taking the total to four this year. Given the 2020 Rothamsted BBRO virus yellows forecast they may well need every one of them.
Following the exceptionally warm winter the expected percentage of virus yellows in crops by the end of August is forecast to be 72 to 95 per cent depending on factory area and drilling date. This is in stark contrast to 2019 when, although 55 per cent of crops showed symptoms, the overall virus level in crops was just 1.8 per cent.
BBRO head of science Professor Mark Stevens says that limiting the spread of virus yellows this year will be a challenge. “Aphids are now flying and approaching the treatment threshold in crops in Cambridgeshire. First sprays will be going on very soon and it’s likely growers will need to continue protecting crops until late June or early July. Some may need more than three sprays.”
This presents a further challenge in resistance management as the two insecticides with emergency authorisations – Biscaya and InSyst – are neonicotinoids and have the same mode of action. Prof Stevens’ advice is: “Alternating insecticides with different modes of action is a recognised anti-resistance strategy so begin with a neonic – either Biscaya or InSyst – then switch to Teppeki for the second spray and back to a neonic for the third.”
If a fourth spray is needed it will have to be another neonicotinoid which he acknowledges is not ideal but, the only option in this emergency situation created by the demise of the seed treatments which saw crops safely through to mature plant resistance.
“Vigilance, using the BBRO’s IPM tools and applying aphicides only at industry recognised thresholds will be crucial this year,” Prof Stevens adds. The yellow water pan network which informs regional risk warning is already live on BBROplus and the emergency authorisation for InSyst can be downloaded from the CRD website.
InSyst Emergency Authorisation – conditions of use