Bayer stops sales of key potato seed treatment Monceren

Agrochemical manufacturer Bayer has halted sales of potato seed treatment product Monceren with immediate effect amid regulatory uncertainty about its future.

The product – which contains the fungicide active ingredient pencycuron – is a dry powder formulation applied to seed tubers at planting to control Rhizoctonia solani, a pathogen that causes symptoms such as stem canker and tuber blemish black scurf.

A statement from Bayer said that pencycuron has been under review by the European Food Safety Authority (Efsa) since 2011.

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In December 2018, Efsa proposed to revoke its maximum residue limit (MRL) on potato and vegetable crops, which would result in all pencycuron registrations for these crops being withdrawn.

An MRL is the highest level of pesticide residue that is legally tolerated in or on food or feed when a product is applied in accordance with its label.

The company then submitted data to defend pencycuron’s use on potato crops, and that this should be under review by regulatory authorities.

However, this process has suffered from regular delays and a final decision has not yet been made.

Spring cut-off for Monceren

If the product were to be revoked this autumn, Bayer predict the likely scenario would mean Monceren users could treat crops up to April 2020.

However, all harvested potatoes produced from treated seed would need to be sold by October 2020, or risk being in contravention of a new MRL.

Any MRL exceedances can lead to packers or processors rejecting produce, at significant financial loss for the grower.

A Bayer statement read: “Given this unclear situation and the potential consequences for potato growers of using a product that could potentially mean concerns selling the harvested crop, being a responsible company, Bayer has decided to stop selling products that contain pencycuron.

“It [Bayer] has also recommended distributors and agronomists advise growers to stop using the product until it receives the final decision of authorities on the MRL value.”

Effective alternatives to Monceren

Yorkshire-based Spud Agronomy’s potato specialist, John Sarup, told Farmers Weekly that growers will miss the cost effectiveness of Monceren for controlling seed-borne rhizoctonia infection in potatoes.

But he said that effective alternatives are available, including Certis product RhiNo DS (flutolanil), which at an application rate of 1.5kg/t is comparable in price.

Bayer’s own Emesto Prime (penflufen) is also an option and, although slightly more expensive, provides good control of rhizoctonia.

While Monceren can be sprinkled over seed tubers in boxes, chitting trays or in the planter hopper, RhiNo DS and Emesto Prime cannot be applied in the same way.

As a result, growers will need to invest in the correct on-planter application equipment to continue using powder seed treatments, which Mr Sarup only sees as a positive.

“[Sprinkling seed treatments] is an outdated method which creates dust at planting. It also gets applied in boxes – and those boxes can be filled with ware tubers at a later date, creating a residue risk. We need to be using these things safely,” he explained.

Mr Sarup added that the cost-effectiveness of Monceren has also led to prophylactic use on some farms and encouraged growers to question the necessity for a seed treatment in the first place.

“Seed tubers should be washed and inspected [for signs of rhizoctonia]. Organisations, such as NIAB CUF, also provide a tuber testing service to see what disease is there and whether a treatment is needed. These are things that we should all be doing.” 

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