# Laboratory and Semi-Field Cage Demography Studies of Diachasmimorpha longicaudata Mass-Reared on Two Ceratitis capitata Strains

## TL;DR

This study compares the reproductive performance of two lines of a parasitoid wasp used to control fruit flies in Argentina under lab and semi-field conditions.

## Contribution

The study provides novel demographic data on parasitoid wasp populations reared on different host strains, aiding mass production and release strategies.

## Key findings

- Dl(Cc-bip) females showed higher reproductive rates than Dl(Cc-tsl) females in laboratory conditions.
- Both lines had similar high reproductive potential in warm seasons but Dl(Cc-bip) remained active in early autumn at low rates.
- Results help improve mass rearing and optimize parasitoid release schedules in semi-arid regions of Argentina.

## Abstract

The reproductive capacity of parasitoid wasps during their lifetime plays a crucial role in understanding their potential as biocontrol agents and the host–parasitoid dynamics. An interesting system to study involves the Southeast Asia-native parasitoid Diachasmimorpha longicaudata and its host Ceratitis capitata, commonly known as the Mediterranean fruit fly or medfly, which is a serious invasive fruit fly pest in Argentina. This study compared reproductive parameters of two parasitoid population lines reared at the biofactory San Juan on different medfly strains. One line was mass-reared on medfly larvae of a genetic sexing strain (=Dl(Cc-tsl)) and the other on larvae of a wild biparental medfly strain (=Dl(Cc-bip)). The goal was to provide information for improving parasitoid mass production and evaluating its performance under natural conditions. For this, laboratory and semi-field cage trials were conducted at the San Juan Biofactory. Firstly, laboratory trials showed that Dl(Cc-bip) females displayed higher reproductive and population rates than those of Dl(Cc-tsl) females. Secondly, semi-field cage trials revealed that females of both Dl(Cc-bip) and Dl(Cc-tsl) had similar and high reproductive potential in late spring and summer, when environmental conditions are temperate–warm. However, unlike Dl(Cc-tsl) females, Dl(Cc-bip) females were reproductively active in early autumn, albeit at very low rates due to colder environmental conditions. The current study provides novel data to improve the productivity of D. longicaudata mass rearing and to achieve the most effective medfly control through parasitoid releases in the semi-arid, fruit-growing areas of Argentina.

Ceratitis capitata (Wiedemann) or medfly is a polyphagous pest of fruit crops worldwide. The Asian-native larval parasitoid Diachasmimorpha longicaudata (Ashmead) is mass-reared at the San Juan Biofactory and is currently released for medfly control in Argentina. Information on parasitoid survival, reproduction, and population growth parameters is critical for optimizing the mass-rearing process and successfully achieving large-scale release. This study provides a first-time insight into the demography of two population lines of D. longicaudata: one mass-reared on medfly larvae of the Vienna-8 temperature-sensitive lethal genetic sexing strain and the other on larvae of the wild biparental medfly strain. The aim was to compare both parasitoid populations to improve mass-rearing quality and to assess performance on medfly in a semi-arid environment, typical of Argentina’s central-western fruit-growing region. Tests were performed under laboratory and non-controlled environmental conditions in semi-field cages during three seasons. Dl(Cc-bip) females exhibited higher reproductive potential than did Dl(Cc-tsl) females under lab conditions. However, both Dl(Cc-bip) and Dl(Cc-tsl) were found to be similar high-quality females with high population growth rates in warm–temperate seasons, i.e., late spring and summer. Dl(Cc-bip) females were only able to sustain low reproductive rates in early autumn, a colder season. These results are useful for improving the parasitoid mass production at the San Juan Biofactory and redesigning parasitoid release schedules in Argentina’s irrigated, semi-arid, fruit-growing regions.