Eavesdropping Kairomone Markers of Interspecific Communication in Predatory and Parasitic Arthropods: A Review.

Abstract

Interspecific chemical communication in insects is quintessential in mediating ecological interactions across trophic levels. Kairomones are semiochemicals emitted by one species (the emitter) and are inadvertently beneficial to another species (the receiver). These chemical markers are particularly critical in prey-predator or host-parasitoid relationships, such as host/prey location and selection. Host/prey bodies and their by-products emit pheromones, volatile and non-volatile cuticular compounds, and induce plant volatiles by oviposition, zoophytophagy, and herbivory, which are copious sources of kairomone signaling. Advances in analytical chemistry and behavioral ecology have enabled the identification and synthesis of such kairomones for integration into integrated pest management (IPM) systems. As semiochemicals are ubiquitous in insects, the literature is robust, and prior reviews often focus on a subset of applications. Here, we aim to consolidate the breadth of current and emerging knowledge on plant- and insect-derived kairomones and highlight their diverse origins, significance in host/prey selection and behavioral orientation, and high specificity in multitrophic interactions. We discuss the compatibility of kairomone-based tools with novel agricultural technologies for pest control, suggesting their potential to enhance crop protection while reducing reliance on broad-spectrum pesticides. We also delineate the limitations of such tools for future research efforts and the feasibility of sampling realistic field headspace volatiles, rather than in laboratories, to identify kairomones, and the formulation of kairomone blends that attract multiple natural enemies simultaneously, rather than kairomones for single natural enemy species, which currently dominate the literature. Most experimental field studies tested kairomones as a standalone pest control tool. We emphasize that combining kairomone use with other IPM components, such as natural enemy-rewarding plants (attract and reward), push-pull companion plants, and beneficial microbial inoculants, would be beneficial. Although complexities abound in formulating and synthesizing kairomones, applying kairomones remains a frontier in sustainable pest management, and opportunities for optimization and integration into IPM programs are abundant.