A New Experimental Setup to Study the Olfactory Behaviour of <i>Trichogramma</i> Egg Parasitoids

ABSTRACT Trichogramma are tiny wasps commonly used in augmentative biocontrol against many Lepidopteran pests. We designed a specific experimental setup to study their olfactory preferences related to egg‐laying behavior. This Y‐shaped olfactometer was coupled with an image‐recognition model, trained with artificial intelligence, to automatically count the number of parasitized eggs. A Bayesian inference pipeline was developed to analyze the data and estimate the attraction or repulsion elicited by the tested odors. We used Trichogramma cordubensis as a model species to validate the new experimental setup, and we demonstrated that T. cordubensis females were attracted to honey and to the sexual pheromone of a potential host ( Mythimna unipuncta ), while they were repelled by vinegar or peppermint essential oil. Overall, this new experimental device will be useful for studying Trichogramma behavioral responses to odors.