An Extension of Authorisation for Minor Use (EAMU) has been granted to a fungicide for the control of downy mildew in field beans.

Bean growers had the option of using Folio Gold to control the yield-sapping disease, but the product has recently been revoked.

This prompted the Processors and Growers Research Organisation (PGRO) to apply for an EAMU for the straight formulation of metalaxyl-M, explains Becky Ward, principle technical officer at the PGRO.

“The removal of Folio Gold has left a big gap in the armoury as it was the only product with activity on downy mildew in beans.”

The disease is very common – particularly in spring beans – and favours overcast and humid conditions like those experienced last season.

Growers apply a fungicide if disease is present at the start of flowering to protect the crop.

Downy mildew can have serious impact on yield in poor years.

Active ingredients

  • Alto Elite chlorothalonil + cyproconazole
  • Amistar azoxystrobin
  • Folio Gold chlorothalonil + metalaxyl-M

Syngenta now hold the authorisation for its product SL567A in field beans, which contains metalaxyl-M at a 465g/litre concentration.

Resistance

Miss Ward notes that some downy mildew pathogens in other crops have developed resistance to the group of fungicides that includes metalaxyl-M.

“Therefore, it must be used with partners with a different mode of action to prevent the build up of resistance to bean downy mildew,” she adds.

Suitable mixing partners include the chlorothalonil/cyproconazole co-formulation such as Alto Elite and azoxystrobin (Amistar), and she advises keeping rates up.

“Full rates should be used to give growers best control of downy mildew and partners can also add activity on chocolate spot and bean rust,” says Miss Ward.

Cost is likely to be a big consideration for growers looking to use the product, with increased seed costs in spring beans this year.

Spring bean seed was also physically bigger, forcing growers to use more to reach optimum plant populations, says AICC agronomist Tod Hunnisett.

“Combined with a herbicide programme that could be around £90/ha if a post-emergence was applied, margins are already going to be squeezed. I won’t be using metalaxyl-M as routine.

“Where conditions are right and the mildew is rife, or on susceptible varieties it will be the only option though,” he says.

Although the product is authorised for use, EAMUs do not guarantee efficacy and toxicity has not been assessed, so the user does so at his or her own risk.

Growers must be in possession of a copy of the EAMU before use, which can be found on the Chemicals Regulation Directorate website.

 Authorisation of Metalaxyl-M
Crop Maximum dose (litres/ha) Maximum number of treatments Maximum total dose Latest time of application
Field beans 0.16 N/A 0.32 14 days before harvest

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