Plant Growth Regulators1
Frederick M. Fishel2
This publication provides the meaning and definition of the term, "plant growth regulator," addresses patterns of use for plant growth regulators, and provides a listing of plant growth regulators registered for use in Florida.
What are plant growth regulators?
Simply put, plant growth regulators (also known as growth regulators or plant hormones) are chemicals used to alter the growth of a plant or plant part. Hormones are substances naturally produced by plants, substances that control normal plant functions, such as root growth, fruit set and drop, growth and other development processes. Plant growth regulators are regulated as pesticides by the Florida Department of Agriculture and Consumer Services (FDACS) and must be registered with the FDACS for lawful use in Florida like any pesticide lawfully used in Florida.
FDACS Definition of "Plant Regulator"
Any substance or mixture of substances intended, through physiological action, for accelerating or retarding the rate of growth or maturation or for otherwise altering the behavior of ornamental or crop plants or the produce thereof, but not including substances intended as plant nutrients, trace elements, nutritional chemicals, plant inoculants, or soil amendments.
History and Use of Plant Growth Regulators
The use of plant growth regulators in agricultural production within the United States began in the 1930s. The first discovery and use of plant growth regulators was with acetylene and ethylene, which enhanced flower production in pineapple. Subsequently, use of plant growth regulators has grown exponentially to become a major component of agricultural commodity production.
Certain herbicides and insecticides that are not true plant growth regulators cause some plant-growth-regulating effects. For example, the widely used insecticide carbaryl is used to thin apple fruit from trees and to aid in encouraging annual bearing.
According to the American Society for Horticultural Science, plant growth regulators fall into six major classes. Table 1, below, lists these classes with the plant development function(s) that are controlled by the plant growth regulators. Table 1 also provides examples of the practical uses with which plant growth regulators are typically associated.
Table 2 provides Florida-specific information on plant growth regulators registered by the FDACS. This table also includes major commodities in the United States that are associated with plant growth regulators and the primary function(s) of plant growth regulators and includes examples of trade names for plant growth regulators registered for use in Florida.