Pythium oligandrum B301 approved until 10 February 2035: an oomycete against grapevine trunk diseases applied by drip irrigation; microbial contaminant limits under OECD Issue Paper No 65, tryptamine below the LOQ of 0.41 g/kg in five batches not shown to comply with the specification, while EFSA did not finalise the assessment for consumers and soil organisms
Commission Implementing Regulation (EU) 2025/102, published on 22 January 2025, approves from 11 February 2025 to 10 February 2035 the new active substance Pythium oligandrum B301 — an oomycete (fungus-like organism) isolated in 2011 from vineyard soil in the Bordeaux region. The application was submitted by Biovitis S.A., the rapporteur was Belgium and the EFSA conclusions date from 18 July 2024. Member States must pay attention to the protection of operators and workers, since microorganisms are regarded as potential sensitisers, and to production quality control in line with the microbial contaminant limits of OECD Issue Paper No 65.
- Representative use (EFSA): professional drip irrigation of grapevines as a preventive treatment inducing systemic resistance to trunk disease pathogens (esca, dieback, black dead arm) — including Phaeomoniella chlamydospora, Phaeoacremonium minimum, Fomitiporia mediterranea, Eutypa lata, Neofusicoccum parvum, Diplodia seriata. The product ‘17PYO1B’ is a wettable powder with 15 g/kg of the strain (nominal 2 × 10⁵ oospores/g); the strain is deposited at the Pasteur Institute collection under number CNCM I-5180.
- Specification and methods (EFSA): 1 × 10⁶–1 × 10⁷ oospores/g in the technical material — a provisional specification, because data on oospore viability and batch representativeness are missing. The species is distinguished microscopically by its spiny-walled oogonium; a SCAR marker to distinguish strain B301 was designed in silico, but without data demonstrating its reliability under experimental conditions. Methods exist for enumerating the microorganism, determining microbial contaminants and tryptamine and oligandrin in the substance; a validated method for oospore viability is missing. Monitoring methods were not required because no residue definition was proposed.
- Metabolites: genes for elicitin-like proteins (including oligandrin) and ‘putative’ genes for tryptamine and NLPs were found in the genome; a hazard was attributed only to tryptamine (proposed classification Acute Tox 4, Skin Sens 1A, Eye Dam 1), with a proposed limit of 0.41 g/kg — it was not detected above the LOQ of 0.41 g/kg in five batches, but it was not demonstrated that these batches complied with the specification (the B301 content was not provided) — EFSA identified a data gap. The strain grows at 35 °C and not at ≥ 38 °C, no data were available for 37 °C; acute toxicity studies showed no toxicity, infectivity or pathogenicity. Of the genus Pythium only P. insidiosum infects mammals.
- What EFSA did not finalise: the consumer risk assessment (no updated literature review on metabolites and no data on the presence of the strain on edible parts), the assessment of persistence and multiplication of the strain in soil with repeated use over the years, the assessment of metabolites in the environment and the risk to soil arthropods and soil microorganisms. It also concluded that the strain does not meet the criteria for inclusion in Annex IV to Regulation 396/2005 (substances without MRLs). The approval act lists conditions on operator protection and microbial contaminants.