Insect Growth Regulators with Juvenile Hormone Activity

Abstract

The term insect growth regulator (IGR) was designed to describe a new class of bio-rational compounds. Through greater selectivity of action these compounds appear to fit the requirements for third generation pesticides, such as the absence of undesirable effects on man, wildlife, and the environment and compatibility with modern insect pest management principles. Although the majority of new com­ pounds in this class are the result of research on insect juvenile hormones, the general term IGR would also accommodate compounds with a different mode of action. The scope of this review, however, is restricted to those IGRs that produce only or primarily juvenile hormone-type responses. The nomenclature of the chemi­ cals and mixtures with JH activity has given rise to much confusion, and terms such as synthetic JH have occasionally been misused. The terms juvenoid, JH mimic, JH analog (JHA), etc all describe the general class of compounds fairly well. In this review we will use the term juvenile hormone (JH) for the natural hormones, IGR when compounds are used with an intention to control pests, and on occasion JHA for less defined situations. IGR, JH, and JHA may therefore occasionally be used for the same compound. Less than ten years have elapsed since the chemical structure of the first insect juvenile hormone (JH I) was elucidated in 1967. This was followed by the positive identification of two closely related structures (JH II and JH III, see Table I). Their presence in various combinations was subsequently proven in various insects, pri­ marily Lepidoptera (82). Schmialek in 1961 ( 180) was the first to elucidate the JH active isoprenoids farnesol and farnesal in excrement of Tenebrio molitor. The low specific activity of these structures made it unlikely, however, that these were actual hormones. It is remarkable that Bowers, Thompson & Uebel ( 18) synthesized the compound that later became known as JH III as early as 1 965, recognized its biological activity, and suggested that it had characteristics of a hormone. Industrial and federal involvement started a great flood of chemical analogs of the juvenile