Seasonal variation in attraction to plant volatiles by Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae)

Authors: Cooper, William - Rodney; Serrano, Jacqueline; Horton, David; OHLER, BONNIE - Washington State University; WATERS, TIM - Washington State University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2024
Publication Date: 5/22/2024
Citation: Cooper, W.R., Serrano, J.M., Horton, D.R., Ohler, B.J., Waters, T.D. 2024. Seasonal variation in attraction to plant volatiles by Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae). Environmental Entomology. 53(4):677-686. https://doi.org/10.1093/ee/nvae048.
DOI: https://doi.org/10.1093/ee/nvae048

Interpretive Summary: Pear psylla is an important pest of commercial pear that will often leave pear orchards to overwinter on conifer shelter plants and return to pear orchards in early spring before trees develop leaves. Insects may use color, taste, or smell to locate and identify host plants, but only a limited amount of information is available on how overwintered pear psylla locate their pear hosts in early spring. Researchers at the USDA-ARS in Wapato WA tested whether winterform and summerform pear psylla are attracted to volatiles (smells) emitted by its pear host and a conifer wintering shelter plant, cypress. They found that pear psylla are attracted to cypress volatiles during winter and early spring, but then shift to an attraction to pear volatiles in late spring and summer. This study is the first to show that pear psylla use plant volatiles for locating host plants while demonstrating a seasonal shift in attraction to plant smells. This information will help the researchers develop management plans targeting the overwintered population as they re-colonize pear orchards in early spring.

Technical Abstract: Pear psylla, Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae), occurs as two seasonal morphotypes. Summerforms occur on pear (Pyrus communis L.) where they are a significant pest. The larger and darker winterform morphotype develops in response to shortening daylengths, and begins winter in reproductive diapause characterized by absence of ovarian development. Diapausing winterforms often leave pear to overwinter on coniferous shelter plants, and then return to pear in late winter and early spring to begin depositing the eggs that produce the first summerform generation. Cacopsylla pyricola adults are attracted to the color of foliage most of the year, but little is known about the role of plant volatiles in host finding and in seasonal dispersal between host and shelter plants by the psyllid. We used a Y-tube olfactometer and choice assays to investigate the response by C. pyricola adults to volatiles emitted by pear and an evergreen tree (cypress) often used as a shelter plant by wintering C. pyricola. Attraction to pear and cypress volatiles varied by season, tree phenology, and psyllid physiology. Cacopsylla pyricola were attracted to cypress volatiles and preferred to settle on cypress shoots during winter and early spring, but then shifted to a marked preference for the pear developmental host in late spring and summer. Female C. pyricola exhibited stronger responses to pear volatiles than did males. Our study is the first to show that plant volatiles have a role in host finding by C. pyricola and provides a foundation for research on chemical ecology and management of C. pyricola.