According to the report from Biological Products Industry Alliance (BPIA), the Agriculture Improvement Act of 2018, also known as the 2018 Farm Bill, was signed into law on December 20, 2018, and provides the first statutory language regarding plant biostimulants in any law in the United States. 

The Farm Bill describes a plant biostimulant as “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 first official language is a major step moving forward for a better understanding of biostimulants, a more regulated biostimulant market, and a wider adoption of using these biologics. 

The original news from BPIA is here https://www.bpia.org/2018/12/biostimulants-in-farm-bill/.