Current distribution of the olive psyllid, Euphyllura olivina, in California and initial evaluation of the parasitoid Psyllaephagus euphyllurae as a biological control candidate

Authors: Hougardy, Evelyne; Wang, Xingeng; Hogg, Brian; JOHNSON, MARSHALL - University Of California; DAANE, KENT - University Of California; PICKETT, CHARLES - California Department Of Food And Agriculture

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2020
Publication Date: 2/26/2020
Citation: Hougardy, E.H., Wang, X., Hogg, B.N., Johnson, M.W., Daane, K.M., Pickett, C.H. 2020. Current distribution of the olive psyllid, Euphyllura olivina, in California and initial evaluation of the parasitoid Psyllaephagus euphyllurae as a biological control candidate. Insects. 11(3):146. https://doi.org/http://dx.doi.org/10.3390/insects11030146.
DOI: https://doi.org/10.3390/insects11030146

Interpretive Summary: The olive psyllid is a new invasive species in the U.S. that could become a serious pest if it spreads to the major olive-growing regions of California’s Central Valley. Here, we report on surveys of the psyllid’s current distribution and its natural enemies in California. We also present results from surveys that were conducted in the psyllid's native region to obtain parasitic wasps that may help control this pest. Tests were conducted with one parasitic wasp from the olive psyllid's native region to ensure that it would not attack native psyllid species if it were ever released in California. The psyllid currently appears to be restricted to the California coast between Monterey and San Diego; it has not been reported on olives in central and northern California. One parasitic wasp species was frequently collected in the psyllid's range, and was brought to quarantine facilities in the U.S. for testing. It did not parasitize or feed on any of the three native psyllid species that it was tested on, indicating that it likely poses little danger to native psyllid species.

Technical Abstract: The olive psyllid, Euphyllura olivina (Costa) (Hemiptera: Liviidae), is a newly invasive species to California that has the potential to become a serious economical pest if it reaches the olive production regions of California’s Central Valley. Here, we report on surveys undertaken in California to assess the psyllid’s current distribution and the occurrence of parasitism. Additionally, we present the results of foreign collections of olive psyllid parasitoids and initial non-target studies with a possible biological control agent, the Mediterranean parasitoid Psyllaephagus euphyllurae (Masi) (Hymenoptera: Encyrtidae). The current distribution of the psyllid appears to be limited to the California coast between Monterey and San Diego; there have been no reports of infestations on olives in the major production areas of central and northern California. Psyllaephagus euphyllurae was the primary parasitoid found in our foreign collections. The potential non-target impact of P. euphyllurae was tested on three native North American psyllid species: Neophyllura arctostaphyli Schwarz, Euglyptoneura nr. robusta and Calophya nigrella Jensen. No P. euphyllurae developed on the non-target species during no-choice tests. Behavioral observations in choice tests confirmed no attack on the non-target hosts, although the parasitoid did remain longer on N. arctostaphyli-infested manzanita plants, and revealed no host feeding behavior.