A campaign promoting new application guidelines for key insecticide chlorpyrifos has received strong industry backing, raising hopes it will lead to a regulatory breakthrough to keep products containing the chemical from being banned.
Such products are a valuable weapon in the arable growers' armoury against wheat bulb fly and orange wheat blossom midge. But they are at risk of being deregistered following a routine EU/UK review.
A new risk assessment for the chemical has resulted in a revised safe concentration of 0.1 parts per billion in watercourses of chlorpyrifos to protect aquatic organisms - the equivalent of one drop of ink in 10 large swimming pools.
Speaking at the Chlorpyrifos: Say No To Drift campaign launch at Peterborough last week, Dow's ecotoxicologist, Steve Norman, said such tiny concentrations meant existing label no-spray buffer zones of 5m for a boom sprayer were no longer adequate.
Extending the buffer zones to the maximum 20m allowed in the UK would still put watercourses at too high a risk from drift using standard 03 flat fan nozzles at 2 bar pressure. The margin would need to be pushed out to a totally impractical 75m, he explains. "According to existing UK policy, chlorpyrifos products cannot be re-approved."
However, extensive studies showed using LERAP three star-rated low-drift (air-induction) nozzles used in conjunction with a 20m buffer zone did meet the new criteria.
As such, the three major approval holders of UK products - Dow AgroSciences, Makhteshim Agan and Headland Agrochemicals - have made that combination a requirement when applying chlorpyrifos. They aim to use the ADAS co-ordinated campaign to get 100% of sprayer operators abiding by the guidelines from now on. "It's simply a case of no drift or no chlorpyrifos," said Mr Norman.
The launch comes weeks before the key wheat bulb fly spray campaign kicks off. The hope is that rapid uptake of the new recommendations during this time, buoyed by cross-industry support, will give the Chemicals Regulation Directorate enough confidence to re-register chlorpyrifos using low-drift nozzle technology with an appropriate buffer zone when it makes its decision later in the year. Currently all CRD risk assessments are based on conventional nozzles.
Success will be measured by monitoring of use of low-drift nozzles by the Pesticides Usage Survey Group. Andrew Speed, Headland Agrochemicals' national technical manager, said all agrochemical distributor members of the Agricultural Industries Confederation had been informed, all Association of Independent Agronomist members had been contacted and NFU and ADAS were also closely involved.
"The subject will be covered at all agronomists' update meetings, and we will be pushing the message out at shows like LAMMA, Cereals 2012 and through the press."
Hutchinsons' technical manager, Dick Neale, said the new guidelines would be flagged up on advice sheets every time chlorpyrifos was recommended.
"The new guidelines will need to be employed for January wheat bulb fly applications onwards." In the absence of chlorpyrifos, yield and quality losses would be significant, particularly for milling wheat, he added.
Careful planning would be needed to abide by the new guidelines, Mr Neale advised. Many areas subject to wheat bulb fly attack were bordered by dykes and more care would also be needed when mixing chlorpyrifos with late T2 or early T3 fungicides for orange wheat blossom midge control to ensure these partner products were recommended for low-drift nozzle application.
Operators also needed to be aware that many low-drift nozzles lost their LERAP three-star rating once sprayers exceeded 8kph, he warned.
A spokesman for HSE said: "CRD is aware of the Chlorpyrifos: Say No to Drift campaign and is watching this with interest. The use of low drift nozzles as risk mitigation measures is not currently part of the pesticides risk assessment. We are unable to comment more specifically at this stage." A CRD decision is expected in the first half of 2012.
Products at risk
Dow - Dursban WG; Equity
Headland - Cyren; Ballad
Makhteshim - Alpha Chlorpyrifos; Pyrinex
New guidelines
All sprayer operators must:
• Use LERAP low-drift, three-star rated nozzles
• Adopt a 20m buffer zone (1m for dry water bodies)
Remember, drive at appropriate speed to maintain three-star rating
Chlorpyrifos - a key arable active
Winter wheat accounts for about 80% of the total area treated with chlorpyrifos - about 800,000ha in 2008.
Wheat bulb fly is a key target. Chlorpyrifos is applied at egg hatch, killing larvae before they reach the plant. Alternative seed treatments (fludioxinil + tefluthrin) can be effective but drilling needs to be delayed until November, says Mr Neale. The other option is a dimethoate deadheart spray, but this is generally less effective than chlorpyrifos.
Chlorpyrifos is also important for orange wheat blossom midge control, killing adults, eggs and newly-emerged larvae over a four to 10-day spray window. Alternatives like lambda-cyhalothrin and thiacloprid are only effective against adults, and timing is critical, he says.