Affect of food provisioning on survival and reproductive success of the olive fruit fly parasitoid, Psyttalia lounsburyi, in the field

Authors: Williams, Livy; POINTURIER, OLIVIA - Montpellier Supagro – International Center For High Education In Agricultural Sciences; DESCHODT, PAULINE - Simon Fraser University

Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 2/25/2019
Citation: Williams III, L.H., Pointurier, O., Deschodt, P. 2019. Affect of food provisioning on survival and reproductive success of the olive fruit fly parasitoid, Psyttalia lounsburyi, in the field. Arthropod-Plant Interactions. https://doi.org/10.1007/s11829-019-09684-1.
DOI: https://doi.org/10.1007/s11829-019-09684-1

Interpretive Summary: Different pest control approaches can be integrated to enhance pest suppression to a greater level than if the approaches were used singly. For example, releases of beneficial insects to control crop pests might be aided by provisioning the beneficial insects with food subsidies to provide sustenance that supports physiological maintenance, longevity, dispersal, and reproduction. The availability of food resources is especially important for beneficial insects that inhabit agricultural fields where nectar and other foods are scarce. The olive fruit fly is a major pest of olives in California, and foreign exploration for natural enemies has led to the discovery of a beneficial insect that attacks the olive fruit fly. A biological control program centered on releases of this beneficial insect is currently underway to protect California olives from the fly. However, olive orchards are mostly devoid of food, e.g., nectar, and newly emerged adults of the beneficial insect have a limited supply of energy, and die in only a few days without access to food. Thus, provision of a food resource might increase the survival and reproductive lifespan of the beneficial insect, and thereby enhance its impact on the olive fruit fly. We conducted a study in an olive orchard where the longevity and reproductive success of the beneficial insect were evaluated with and without access to food (honey+pollen mixture). Our study showed that food provision increased the beneficial insect’s survival and its reproductive success. In particular, the reproductive lifespan was greater in fed beneficial insects; parasitism rates, offspring production, and the number of beneficial insects that attacked olive fruit fly were also increased, but to a lesser degree. Use of food provisioning approaches to help nourish beneficial insects that have been released for olive fruit fly control appears to be a promising strategy. Future studies should further evaluate the effect of food provisioning on the reproductive success of beneficial insects attacking the olive fruit fly, and identify what type of resources best enhance the beneficial insect’s impact on this pest.

Technical Abstract: Conservation biological control offers approaches that can be integrated into classical biological control programs to enhance pest suppression. Food sources, such as nectar and honeydew, provide sustenance to support physiological maintenance, longevity, dispersal, and reproduction. Food subsidies can increase a parasitoid’s fecundity either by extension of the reproductive lifespan, increasing the rate of egg maturation, or both. The availability of food resources is especially important for parasitoids that inhabit agroecosystems where nectar and honeydew are scarce. The olive fruit fly, Bactrocera oleae, is a major pest of olives in California, and foreign exploration for natural enemies has led to the discovery of a parasitoid, Psyttalia lounsburyi, that attacks B. oleae. A classical biological control program for P. lounsburyi is currently underway to protect California olives from the fly. Pysttalia lounsburyi emerges with a limited supply of energy, and dies in a few days without access to food. We conducted a field study where female-male pairs of P. lounsburyi wasps were caged with B. oleae-infested olives, and provisioned either with food (honey+pollen mixture) and water, or water only. Our study showed that adult feeding is crucial to P. lounsburyi survival and fecundity under field-cage conditions. Food provision increased P. lounsburyi survival and several components of the wasp’s reproductive success; nevertheless, parasitism rates and offspring production were relatively low. This was probably due, at least in part, to location of host larvae in enemy-free space ‘beyond the reach’ of the wasp’s ovipositor. Sex ratio of offspring was male-biased, perhaps due to inbreeding in the laboratory colony from which P. lounsburyi was sourced. Female wasps carried ca. 25-35 eggs at their time of death, suggesting that they were time limited rather than egg limited. Integration of conservation biological control (e.g., food provisioning) and classical biological control (release of an exotic natural enemy) has promise to suppress olive fruit fly populations. Future studies should further evaluate the effect of food provisioning on P. lounsburyi reproductive success under open field conditions.