Populations of Bactrocera oleae (Diptera: Tephritidae) and Its Parasitoids in Himalayan Asia

Authors: BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL); Hoelmer, Kim; PICKETT, CHARLES - California Department Of Food And Agriculture; KIRK, ALAN - European Biological Control Laboratory (EBCL); HE, YURONG - South China Agricultural University; MAHMOOD, RIAZ - Center For Agricultural Bioscience International, Cabi; DAANE, KENT - University Of California

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2015
Publication Date: 11/26/2016
Citation: Bon, M., Hoelmer, K.A., Pickett, C.H., Kirk, A.A., He, Y., Mahmood, R., Daane, K.M. 2016. Populations of Bactrocera oleae (Diptera: Tephritidae) and Its Parasitoids in Himalayan Asia. Annals of the Entomological Society of America. 109:81-91. doi: 10.1093/aesa/sav114.

Interpretive Summary: Since the introduction of the invasive olive fruit fly into California more than a decade ago, it has become the most important pest of olives in North America. In support of an ongoing biological control program against the fly in California, we collected wild olives in the foothills of the Himalayas (China, Nepal, India, and Pakistan) to discover new natural enemies of the fly. Wild olive is sparsely distributed in much this region, partly due to land clearing and cutting for firewood, and fly-infested fruit was scarce. Flies were collected in the greatest numbers in Pakistan, and also from rare populations in China, which is the first record of olive fly in China. Natural enemies were also found that were associated with the flies. We analyzed genetic markers in Asian fly specimens that conclusively identified them as true olive flies, and we compared the levels of genetic variability in Asian fly populations with those in other parts of the fly’s natural range in Europe and Africa. The Chinese population of flies represents a distinctive branch of flies that has separated from its relatives elsewhere. We discovered a new natural enemy of olive fruit fly in China, which reinforces the possibility of finding new biocontrol agents of olive fruit fly elsewhere in the Himalayan region.

Technical Abstract: For a biological control program against olive fruit fly, Bactrocera oleae Rossi, olives were collected in the Himalayan foothills (China, Nepal, India, and Pakistan) to discover new natural enemies. Wild olives, Olea europaea ssp. cuspidata (Wall ex. G. Don), were sparsely distributed and fly-infested olives were often scarce. Wild olives were most widespread in Pakistan, where fly infestation was as high as 30%. Infested olives in southwestern China were rare, reaching only 5% at a few sites. This represents the first record of B. oleae from China. No B. oleae were recovered from collections in India or Nepal. Flies were parasitized by Psyttalia ponerophaga in Pakistan and a Diachasmimorpha species in China. NADH dehydrogenase gene (mtND1) sequences from fly specimens were compared with the existing Genbank database. Genealogical relationships among B. oleae ND1 haplotypes were depicted by statistical parsimony. Although Chinese flies were identified morphologically as B. oleae, their unique ND1 haplotype did not connect to the B. oleae ND1 haplotype network to which Pakistani flies belong, suggesting a cryptic species. However, the overall 2.8% genetic divergence between the Chinese haplotype and all other B. oleae haplotypes was lower than divergence between two closely related congeners, B. biguttula and B. munroi, supportive of a highly divergent ancestral Chinese B. oleae lineage. Laboratory crosses between Chinese and French flies support this conclusion. Confirming the taxonomic status of Chinese flies will require analysis of nuclear genes, detailed morphometric analysis, and more extensive crossing studies. The survey reinforces the possibility of finding new biocontrol agents of olive fruit fly in the Himalayan region.