Wheat bulb fly egg hatch is under way at four out of five monitoring sites, ADAS has confirmed.
Soil sampling carried out by the Dow AgroSciences and ADAS Pestwatch service shows that wheat bulb fly egg hatch is under way in Cambridgeshire, Hertfordshire, north Lincolnshire and Suffolk.
However, by Monday (23 January), there was still no egg hatch in north Yorkshire.
ADAS entomologist Steve Ellis says growers in high-risk areas where hatch is under way can start to apply chlorpyrifos.
“The Pestwatch service will give you an indication of when is best to go on with your spray, so I would recommend that growers refer to the Dow Pestwatch website for regular updates,” he says.
“The sprays should be timed to coincide roughly at the start of egg hatch, which the monitor service provides.”
The standard threshold is 250 eggs/sq m – the equivalent of 2.5m eggs/ha.
Dr Ellis says wheat bulb fly egg counts are on average around 50% lower this year compared with last year.
“One in five sites are potentially still at risk from the pest, which in severe infestations can cause significant crop loss,” he adds.
An industry stewardship initiative – the chlorpyrifos: Say NO to Drift campaign – has been unveiled this season with the aim of protecting the future availability and use of insecticides containing chlorpyrifos.
DowAgrosciences toxicologist Steve Norman urges growers to demonstrate their commitment to safe use of chlorpyrifos by visiting the website www.saynotodrift.co.uk and signing up to the campaign.
He reminds growers that when spraying any chlorpyrifos product they should use a LERAP rated three-star nozzle and adopt a 20m buffer zone near to watercourses or 1m near to dry ditches.
The advice comes after the Chemicals Regulation Directorate (CRD) changed their risk assessment and introduced stricter criteria for the use of chlorpyrifos.
Mr Norman said: “The low drift nozzles must meet the three-star rated LERAP specifications and they must be used in the right conditions, including spray pressure and forward speed.
“If growers fail to demonstrate the use of these low-drift nozzles through chlorpyrifos then there’s a risk we could use this valuable chemical along with others.”