Eddie Simons in WSDA Ag Briefs
Pesticide Registration and Licensing

A stimulating look at plant biostimulants

If you garden, farm, or endeavor to grow anything in the ground, you’ve become the target audience for a new product marketed under the vague, hyper-modern moniker “biostimulant.”

Biostimulants are generating so many claims and so much hype, regulators are racing to keep pace with how to evaluate and classify them. Although the products have been around for decades, they have just recently been recognized in the 2018 Farm Bill.

Even as biostimulants make the first steps towards widespread conventional use, the U.S. Department of Agriculture (USDA) and state agencies around the country haven’t agreed on where biostimulants fit in and how it should be regulated, though they seem to belong somewhere near fertilizers, pesticides, or soil amendments.

What is a biostimulant?

According to the 2018 Farm Bill, a “plant biostimulant” is “…a substance or micro-organism that, when applied to seeds, plants, or the rhizosphere, stimulates natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress, or crop quality and yield.” This includes a wide variety of materials, including

• Plant extracts
• Humic/fulvic acids
• Proteins and amino acids (plant or animal origin)
• Beneficial elements [Silicon (Si), Aluminum (Al)]
• Beneficial bacteria
• Beneficial fungi [mycorrhizae]

Why are people interested in using biostimulants in ag?

There is a renewed interest in biostimulants because of what they have the potential to do. Some of the claimed benefits include

• Improved plant and root growth
• Improved nutrient use
• Resistance to drought, insects, and diseases
• Improved end use quality of the harvested crop

What plants are they made from?

The most common plant extract used in biostimulants is from kelp, but others include soy protein hydrolysate, willow bark extract, stinging nettle extract, Yucca extract, and aloe extract.

Are they a pesticide? If not, what’s the difference?

Some of these biostimulants meet the definition of a pesticide. For example, seaweed extract contains relatively high levels of phyto-hormones, which increase plant and root growth. This would fall under the pesticide category of “plant regulator” under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

Other biostimulants stimulate a plant’s defense mechanisms allowing it to better defend against insect and or disease pressure. This is called Systemic Acquired Resistance (SAR) and is another form of pesticide.

Most biostimulants that work on nutrient functions are not pesticides. For example, soil applied humic acid can combine and amplify the availability of nutrients in the soil, allowing for easier uptake by the plant roots. Plus, mycorrhizae will extend throughout the soil, transporting nutrients to the plant roots.

Are there regulatory issues people should know about?

The term “biostimulant” seems to be a marketing term. Parts of the biostimulant industry are trying to separate biostimulants from the definition of a pesticide, but at this point it has not happened. The common definitions of pesticide, fertilizer, soil amendment are all related to primary functions and claims of the product.

Most biostimulants seem to focus on secondary functions and claims, for example, that the hormones will increase root growth, which will improve drought resistance. If the claim is drought resistance, producers tend to think it should not be regulated as a pesticide.

Does WSDA have recommendations about biostimulants?

WSDA does not currently regulate biostimulants differently than any other product. If a biostimulant meets the definition of a pesticide, it will be regulated as a pesticide.

The Association of American Plant Food Control Officials (AAPFCO) recently sent a letter to the USDA with an opinion on biostimulants and their regulatory status.

“Creating a single regulatory structure for all products marketed as biostimulants would create confusion with regulators, industry and consumers,” the letter stated. “Products should be regulated based on their intended function, not based on a broad marketing term.”

This letter was intended to help USDA write their report to Congress and the President as mandated by the 2018 Farm Bill. This report will detail regulatory and non-regulatory options for oversight of biostimulant distribution.

WSDA continues to follow federal and Washington State laws related to pesticides and fertilizers, including biostimulants. We regulate products based on their intended function, not a non-specific marketing term. We will continue to follow the actions being taken at the federal level regarding biostimulant regulation.

What should I do?

When looking at new products, think about why you are applying them. If the purpose is to control a pest or stimulate plant growth (beyond simple nutrition), check that the product is registered as a pesticide. If the purpose is to supply nutrients to the plant, check that it is registered as a fertilizer. Most of all, enjoy your time in the garden or with your plant.