Chemical ecology of an emerging thrips pest: Evaluating semiochemical-based push – pull strategies for Thrips parvispinus

Abstract: Thrips parvispinus is an emerging invasive pest threatening greenhouse crop
production in Canada. This species causes direct feeding damage and can indirectly impact
crops through the transmission of plant pathogens. Sustainable management strategies are
needed, particularly those that integrate semiochemical-based approaches and biological
control. Herbivory-induced plant volatiles (HIPVs) play important roles in insect host selection and predator foraging behaviour, yet little is known about how T. parvispinus and its natural enemies respond to these chemical cues. This study evaluated semiochemical-based pest management strategies by examining (1) the behavioural response of T. parvispinus to the green leaf volatile (Z)-3-hexenyl propanoate ((Z)-3-HP); and (2) the olfactory preference of the predator Orius insidiosus for herbivory-induced plant volatiles emitted by pepper plants infested with either T. parvispinus or the cosmopolitan thrips, Frankliniella occidentalis. Behavioural responses were assessed using Y-tube olfactometer assays under controlled laboratory conditions. Overall, none of the concentrations of (Z)-3-HP tested produced significant attraction or repellency for T. parvispinus, however responses varied numerically across doses and high non-response rates were observed. Similarly, O. insidiosus females exhibited weak numerical preferences for thrips-infested plants over uninfested plants and a slight preference toward F. occidentalis– compared to T. parvispinus-infested plants; however, none of these responses were statistically significant. High non-response rates across assays suggest that volatile cues alone may be insufficient to drive strong behavioural responses, especially in young O. insidiosus adults with no prior thrips handling experience. These findings do, however, provide a baseline on the chemical ecology of T. parvispinus and its interactions with one of its key biological control agents and highlight opportunities for further investigation using whole-plant assays, optimized volatile delivery systems and integration with biological control strategies.