Influence of Anastrepha host fruit size over parasitism by Diachasmimorpha longicaudata in open-field augmentative releases

Abstract

Fruit size can act as a physical barrier providing refuge for larvae of pest Anastrepha species against parasitoid attack. Therefore, the aim of this study was to evaluate the influence of fruit size in six fruit species infested by Anastrepha larvae on the parasitism of Diachasmimorpha longicaudata after its augmentative release. About 1500 parasitoids were weekly released in disturbed wild vegetation patches. Fruit sampling was performed at the Coastal Lowlands of the Soconusco Region, southeastern Mexico, between June 2021 and October 2022. Overall, 310 ripe fruits belonging to grapefruit, creole mamey (large-size fruits), sweet orange, creole mango, wild guava (medium-size fruits), and wild hog plum (small-size fruit) were collected. The length, frontalwidth, lateral width and pulp thickness of all sampled fruits were measured. Such physical characteristics are indicators of the fruit size. Fruit collection was performed 48 h after release. Results indicated an inverse correlation between fruit size and parasitism, with a significant r2 value higher than 75%. Host larvae in all fruits were parasitised only by D. longicaudata. The highest mean parasitism, which exceeded 90%, was recorded on hog plum and the lowest, below 20%, on Citrus spp. and mamey. Results corroborated the influence of host fruit size on parasitism levelsby D. longicaudata regardless of its large-scale, open-field releases. Augmentative releases of D. longicaudata can be focused on wilderness areas with prevalence of medium-size to small-size Anastrepha host fruits. This would encourage long-term sustainable conservation of released parasitoid populations.