Characterizing Substrate-Borne Vibrational Mating Signals Produced by Pear Psylla, Cacopsylla pyricola (Hemiptera: Psyllidae)

J Insect Behav https://doi.org/10.1007/s10905-023-09839-2 RESEARCH Characterizing Substrate‑Borne Vibrational Mating Signals Produced by Pear Psylla, Cacopsylla pyricola (Hemiptera: Psyllidae) Dowen Mae I. Jocson · Mark T. Gonzales · David R. Horton · Louis B. Nottingham · Elizabeth H. Beers · Liesl C. Oeller · David W. Crowder Received: 13 April 2023 / Revised: 26 August 2023 / Accepted: 6 September 2023 © The Author(s) 2023 Abstract Tactics that manipulate insect behavior are a component of many pest management strategies. Pheromone-based mating disruption is one such tactic widely used in agricultural systems, but few studies have assessed disrupting other mate communication mechanisms, such as acoustic signals. The most destructive pear pest in the Pacific Northwest USA, pear psylla (Cacopsylla pyricola) is believed to use acoustic signals to find mates, making it a candidate for this type of disruption. This species has two adult morphs, overwintering adults (winterforms) Supplementary Information The online version contains supplementary material available at https://doi. org/10.1007/s10905-023-09839-2. D. M. I. Jocson (*) · M. T. Gonzales · L. C. Oeller · D. W. Crowder Department of Entomology, Washington State University, Pullman, WA, USA e-mail: D. R. Horton Agricultural Research Services, United States Department of Agriculture, Wapato, WA, USA L. B. Nottingham Department of Entomology, Northwestern Washington Research and Extension Center, Washington State University, Mount Vernon, Pullman, WA, USA E. H. Beers Department of Entomology, Tree Fruit Research and Extension Center, Washington State University, Wenatchee, WA, USA that emerge in the spring and subsequent generations (summerforms). Our study characterized the mating signals for both sexes and morphs of pear psylla, and assessed whether temperature and previous exposure to adult conspecifics altered signals and likelihood of signaling. While there are descriptions for acoustic signals of other psyllid species, this study provides the first evidence that C. pyricola communicates acoustically. The two sexes communicate via duetting; males signal to attract a female and the female signals back if she is receptive for mating. We showed that both morphotypes’ male signals contain a group of chirps followed by a trill, while females respond with chirps. Male signal trills differed significantly in frequency (Hz) between winterform and summerform psylla. The signal frequency among morphs also had a positive linear relationship with temperature, suggesting that dissimilarity in signals among morphs had some relationship to temperature. Males were more likely to signal when they had previous exposure to females compared to males without exposure to females. Our results provide new information on how pear psylla communicate acoustically for mating, advancing the potential to develop mating disruption strategies for integrated pest management (IPM). Keywords Psylla · vibrational communication · pear · mating behavior Vol.: (0123456789) 13 J Insect Behav Introduction Sustainable pest management in agricultural systems relies on strategies that reduce overall insecticide use and exploit species-specific behaviors or life history traits (Weddle et al. 2009). Mating disruption, for example, is used to exploit a pests’ mating behavior in ways that reduce mating opportunities (Cardé and Minks 1995). Many insects communicate with mates using species-specific pheromones that can be synthesized and used to interfere with mate-location and, consequently, female-production of fertile eggs (Cardé and Minks 1995). Pheromone-based mating disruption has in turn been used to control species such as domestic silk moth, oriental fruit moth, and codling moth (Butenandt 1959; Wright 1964; Ridgway et al. 1990; Cardé and Minks 1995; Brunner et al. 2002; Howse et al. 2013). While insects also communicate with potential mates through nonchemical means, such as acoustic signals, there are few examples of mating disruption tactics that disrupt signals other than pheromones (Miller and Gut 2015). Many insects use vibrational signals for communication (sometimes referred to as songs) and the study of substrate-borne vibration has a long history; this form of communication is common in many Hemipteran, Coleopteran, and Hymenopteran insect families, including pest groups (Cocroft and Rodríguez 2005). Studies show that sap-feeding pests such as Homalodisca vitripennis (Nieri et al. 2017), Diaphorina citri (Mankin et al. 2015), Halyomorpha halys (Polajnar et al. 2016), and Cacopsylla pyri (Eben et al. 2015) all use substrate-borne vibrational signals that might be targeted to reduce mating success. Although recent advances in vibration sensing and recording technologies offer an opportunity to disrupt this form of communication, there are few examples of such behavioral manipulation within integrated pest management (IPM) programs outside of brown marmorated stink bugs (Mazzoni et al. 2017b) and in two leafhopper pests in grapes (Mazzoni et al. 2009, 2017a; Nieri et al. 2017). One potential barrier to using vibrational signals for pest management is that insect signals are rarely static, with signal characteristics affected by variation in abiotic or biotic conditions (McNett et al. 2010; Virant-Doberlet et al. 2014; Oberst et al. 2019). In the Enchenopa binotata species complex of treehoppers, for example, temperature fluctuations affect Vol:. (1234567890) 13 characteristics of male mating signals as well as responses by females (Jocson et al. 2019). This suggests that changes in temperature can induce physiological changes that allow males to produce vibrations at varying frequencies. This suggests disruptive signals might need to be modulated to match speciesspecific patterns under various temperature ranges, or based on other abiotic factors. Biotic factors, such as the presence of conspecifics or natural enemies, or the number of mating attempts, may also affect mating behavior (Fowler-Finn and Rodríguez 2012). The goal of this study was to characterize vibrational communication signals of pear psylla, C. pyricola, as a step toward testing an acoustic mating disruption approach. Pear psylla is the most economically damaging pest of pears in Washington, Oregon, and California (Follett et al. 1985; DuPont et al. 2021; Murray et al. 2021). Pear psylla has two morphs: the winterform and the summerform (Oldfield 1970), and we characterized vibrational signals of male and female psylla of both morphs. After signals were characterized, we assessed how temperature variation and previous exposure to adult conspecifics affected signal characteristics. We predicted that psylla would produce higher frequencies (Hz) in their signals at warmer temperatures (Jocson et al. 2019), and that males would be more likely to produce mating signals if they had previously encountered females compared to naïve males. Our experiments characterizing p (...truncated)