Update On Root-Promoting Chemicals and Formulations
Michael A. Dirr
In my 20 years as a member of this society, I have read more papers and heard more questions about root-promoting chemicals than any other subject. Members have eagerly tested chemicals and formulations, but none has been as effective as indolebutyric acid (IBA) and naphthaleneacetic acid (NAA) (Dirr, 1981, Dirr and Heuser, 1987).
A major hurdle to the development of new root-promoting chemicals, particularly in the United States, is the EPA registration process. The chemical must undergo screening for toxicity to a wide range of organisms. Since the root-promoting chemicals are categorized as minor-use compounds, companies are not enthusiastic about spending the necessary money to bring them to market. A recent estimate placed the cost between 4 and 10 million dollars for the introduction of a new non-food chemical like IBA.
IBA and NAA are legally registered for use in plant propagation. Theoretically, plant propagators cannot buy and use the actual chemicals. They must
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