Laminarin

How does laminarin work, and is it allowed?

By Tina Jensen Augustine

Laminarin is a pesticidal substance that the NOSB formally recommended be considered nonsynthetic and acceptable for use on organic operations in 2015. It is a naturally occurring polysaccharide in plants that is commercially extracted primarily from the brown algae Laminaria digitata. It is intended for preventative use, before infection occurs.

Laminarin functions by stimulating (eliciting) a plant’s natural defense mechanisms against disease pathogens. It triggers a cascade of chemical signaling pathways that lead to increased production of defense proteins, enzymes and other chemicals that exert antifungal and antibacterial activities. These responses can limit infection and deter its spread throughout the plant. Laminarin treatments have also been found to make plants more attractive to wasps that parasitize insect pests.

In 2010, the EPA found that laminarin was toxicologically innocuous and did not adversely affect non-target organisms. EPA registered label uses cover a wide variety of crops such as strawberries, bush berries, bulb crops, brassicas, cereal grains, leafy greens, tree fruit, grapes and others. Laminarin can help protect against various blights, rusts, leaf spots, mildews, fruit rot and other plant diseases.

Laminarin can be extracted by several methods. Extractions using Laminaria digitata as the source material often involves pH adjustment with acids such as sulfuric or hydrochloric acid, followed by several filtering steps and finally neutralization with sodium hydroxide. The use of acid in this process does not change the chemical composition of laminarin. The lowered pH prevents the co-extraction of other compounds from the brown algae, such as alginates. This makes the filtering step much easier. Neutralization with sodium hydroxide means that residual sodium and sulfate ions remain in the solution once extraction is complete. These are not removed.

Laminarin was originally petitioned for addition to 205.601 (allowed synthetics) of the National List in 2013. Other aquatic plant extracts obtained using the bases potassium or sodium hydroxide are already listed as synthetic on the National List at 205.601(j)(1). However, in 2014, the NOSB Crops Subcommittee issued a proposal in which the majority considered laminarin to be nonsynthetic. Conversely, the minority felt that the substance as described in the petition could contain residual levels of sodium sulfate that would render the material synthetic. OMRI was contracted by the National Organic Program (NOP) to produce a limited-scope technical report on the manufacturing process of laminarin for the NOSB. This 2015 report indicated that the extraction process described does not chemically change the laminarin, and concluded that residual levels of sodium and sulfate ions would not have a technical effect in the product. Additionally, the quantities of these residual substances would be small enough that the EPA would likely not require they be reported on a Confidential Statement of Formula. Based on this information, the NOSB voted at the October 2015 meeting to classify laminarin, as petitioned, as nonsynthetic. Nonsynthetic substances used for organic crop pest control are allowed unless specifically listed at 205.602. Since the NOSB’s decision, the NOP has published NOP 5033-1: Guidance, Decision Tree for Classification of Materials as Synthetic or Nonsynthetic. The NOSB used a draft version of this guidance when making their determination. Laminarins manufactured using processes consistent with this guidance are allowed as pest control substances in organic crop production.

The EPA lists laminarin as exempt from the requirement of a tolerance on food when applied pre-harvest. Vacciplant, the trade name under which laminarin is marketed, is currently EPA registered.

This article was originally published in the spring 2016 edition of the OMRI Materials Review newsletter, and was reviewed and revised in August 2020 by Senior Technical Coordinator Peter Bungum.