Kairomones

By Tina Jensen Augustine

Are kairomones considered pheromones, and are they allowed?

The National List at §205.601(f) allows for the use of synthetic pheromones in insect management. These synthetic pheromones are copies of certain natural substances released by organisms as communication signals. “Semiochemical” is the general term used to describe chemicals emitted by an organism that influence the physiology or behavior of other organisms. Pheromones are semiochemicals that influence the physiology or behavior of members of the same species. They include sex attractants, alarm substances, aggregation pheromones and trail markings. Pheromones are commonly used in traps and lures, attract-and-kill systems, and in confusion and disruption of insect mating.

While pheromones carry information from one individual to another of the same species, allelochemicals are semiochemicals that carry signals from one species to a different species. There are various classes of allelochemicals and they are grouped based on who benefits from the chemical signal. Kairomones are allelochemicals where the chemical signals are favorable to the organism that receives the signal. A familiar example is the lactic acid component of human sweat that attracts the mosquito Aedes aegypti. Allomones are allelochemicals such as repellents or defense compounds that benefit the organisms which emit them, and synomones are those that benefit both the sender and the receiver of the chemical message.

Because the terms above are based on the function of the chemicals rather than the chemicals themselves, one must consider not only the source of the substance but also its intended use and mode of action. There are instances where the same chemical could be classified as an allomone, kairomone or pheromone depending on its circumstantial effects. For example, female moths emit a sex attractant chemical (pheromone) that is also emitted by the American bola spiders that prey on male moths (allomone).

Commercial insect control products may contain pheromones and/or kairomones. When pheromones were originally considered for inclusion on the National List in 1995, the National Organic Standards Board (NOSB) Technical Advisory Panel report noted that they disrupt mating patterns of males of target species, and specifically states that the substance “does not affect other species.” This expressly excludes synthetic kairomones from use in organic production under the “pheromones” category. However, plant oils and other nonsynthetic extracts may have functional effects as kairomones. Therefore, while synthetic kairomones are not permitted for use in organic production, nonsynthetic substances which act as kairomones could be employed in accordance with National Organic Program (NOP) regulations.

Revised and updated in March 2019 by OMRI Technical Director Doug Currier. This article was originally published in the Summer 2016 edition of the OMRI Materials Review newsletter.