AAPFCO Plant Biostimulant Microorganism List

This list is intended to specifically identify microorganisms considered to be "plant biostimulants" and to provide accurate identification and permissible labeling claims. This is a communication tool between state control officials and industry and is not an exhaustive list of all microorganisms "allowable" in fertilizers or beneficial substances. Omission of a microbe from this list should not be used as the sole basis for denying registration.

The presence of a "pesticidal property" (Pesticidal) of a microorganism does not indicate that it must be regulated as a pesticide in the absence of pesticidal claims; products should be evaluated on a case-by-case basis according to their claims, intended use, and supporting data. Similarly, low-risk (Risk Group 1) potential pathogens that pose little to no risk for healthy individuals should also be evaluated on a similar case-by-case basis. While these microorganisms may not be considered plant biostimulants, they may prove to be acceptable as general beneficial substances.

Genus / Species Synonyms Accepted Claims

Notes

  • Accepted Claims are not intended to be verbatim. Label claims can vary as long as it adheres to the general intent of the acceptable claims.
  • "Benefical to plants and/or soils" is the default generally acceptable claim, if no additional supported claims have been identified.

Statuses

  • The Pesticidal reference mark indicates that the microorganism may possess pesticidal properties in addition to properties as a plant biostimulant. These microorganisms may still be considered plant biostimulants as long as there are no pesticidal claims or the product is dual-registered as a pesticide and a plant biostimulant.
  • Microorganisms with a Pesticidal reference mark, Pseudomonas toyotomiensis, and Delftia acidovorans RAY 209 are in "Tentative" status. The next vote is for "Tentative" by AAFPCO membership, followed by a possible initial "Official" vote within the Biostimulant Committee at the AAPFCO Summer Annual Conference in August 2026.
  • Except as noted above, bolded & highlighted microorgranisms will have an "official" membership vote at the AAPFCO Summer Annual Conference in August 2026.