Exploring the Kairomone-Based Foraging Behaviour of Natural Enemies to Enhance Biological Control: A Review

Abstract

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

Antenna-Biased Odorant Receptor HvarOR25 in Hippodamia variegata Tuned to Allelochemicals from Hosts and Habitat Involved in Perceiving Preys

“…4,5 Chemical cues play crucial roles in mediating the feeding behavior of predatory natural enemies. 6 Herbivore-induced plant volatiles (HIPVs) and volatile compounds emitted from hosts provide useful information for natural enemies to search and locate target preys. 7 Generally, the H. variegata utilizes a well-developed olfactory system to distinguish odor cues to modulate a series of vital behaviors, in particular prey locating.…”

“…Chemical cues play crucial roles in mediating the feeding behavior of predatory natural enemies . Herbivore-induced plant volatiles (HIPVs) and volatile compounds emitted from hosts provide useful information for natural enemies to search and locate target preys .…”

Determining suitable observation times for testing odor preferences of a parasitoid wasp, Cotesia kariyai, using a four‐arm olfactometer

“…These released plant compounds are known as herbivore‐induced plant volatiles (HIPVs) (Price et al, 1980; Takabayashi & Dicke, 1996; Turlings & Erb, 2018). HIPV composition varies depending on the herbivore species, larval developmental stages, density, and time of day that feeding occurred (Takabayashi et al, 1995; De Moraes et al, 1998; Hare, 2011; Wäschke et al, 2013), providing precise information regarding the presence of suitable host insects for parasitoid wasps (see reviews Turlings & Erb, 2018; Takabayashi & Shiojiri, 2019; Ayelo et al, 2021). Attractiveness of HIPVs to parasitoid wasps has been extensively investigated for decades, because this information can be applied to pest management using natural enemies (Meiners & Peri, 2013; Turlings & Erb, 2018).…”

Volatile organic compounds released by wheat as a result of striped shieldbug feeding and insect behaviour

“…Plant protection mechanisms can provide an alternative to the use of chemical protection products (Bougherra et al, 2015; Erb, 2018; Wonglom et al, 2020), with kairomones providing chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or blends of herbivore‐induced plant volatiles (Ayelo et al, 2021; Turlings & Erb, 2018). Some volatile organic compounds (VOCs) emitted by a plant have a repellent (deterrent) effect on agrophages (Cardoza et al, 2003).…”