Potato seed treatment Monceren is being withdrawn immediately after UK regulators announced an end to the use of the active pencycuron, which was used to control rhizoctonia.

The UK Chemicals Regulation Directorate (CRD) announced an end to the use of Monceren, manufactured by Bayer, as of 25 March 2020, and growers are advised to look at alternatives.

The product is a dry powder formulation applied to seed tubers at planting to control Rhizoctonia solani, a pathogen that causes symptoms such as tuber black scurf and stem canker.

See also: Bayer stops sales of key potato seed treatment Monceren

An EU proposal to cut the maximum residue limit (MRL) for pencycuron earlier this month meant it was still possible that it could be applied to seed planted this spring, But now, the CRD’s announcement means it is no longer possible to apply Monceren for any purpose.

EU proposals

Following the EU’s proposed MRL, Bayer had already advised all users to consider an alternative treatment, such as its own product Emesto Prime (penflufen), as it considered the lower MRL to be unworkable in practice.

“As a responsible company, we advised growers against applying Monceren as soon as the proposed MRL was announced, but we had hoped for a transition period – typically in the region of six months – to allow for returns to be arranged in a timely manner,” said Edward Hagues, Bayer campaign manager for root crops.

The notice for revocation allows three months (until the end of June) to take delivery of returned product and arrange for its disposal. Bayer will take back unopened and undamaged stocks of Monceren. To arrange a return, growers should contact their distributor.

The EU Commission voted in early March to reduce the MRL for pencycuron to 0.01mg/kg, just one-tenth of the previous limit. The new MRL is expected to pass into EU law by June 2020, after which time any treated crop, domestic or otherwise, would have had to meet the new MRL.