Impactos de Heterorhabditis amazonensis GL no parasitismo de Diachasmimorpha longicaudata (Hymenoptera: Braconidae) no controle de Ceratitis capitata(Diptera: Tephritidae)

Abstract

Biological control is increasingly used in fruit fly management programs, particularly through parasitoid releases. In regions with high Tephritidae population density, parasitoids alone are insufficient to keep fly populations below economic damage thresholds, necessitating the adoption of additional control methods or agents. Entomopathogenic nematodes (EPNs) are a viable option as they infect fruit fly larvae after they exit the fruit to pupate in the soil. However, compatibility between these agents must be determined beforehand to prevent mutual interference. Previous studies have shown that EPNs cause higher mortality in Ceratitis capitata (Wiedemann) larvae parasitized by Diachasmimorpha longicaudata (Ashmead) compared to non-parasitized larvae. Moreover, EPN infection has sublethal effects on surviving adult insects, including cuticle discoloration, thinning, anatomical deformities, reduced fertility, and longevity. Therefore, this study aims to track the development of D. longicaudata in C. capitata larvae exposed to the nematode Heterorhabditis amazonensis GL, assess parasitism in infected larvae, and evaluate sublethal effects on the parasitoid. Bioassays were conducted under controlled conditions at the Insect Pathology and Microbial Control Laboratory. Parasitoid development was monitored by dissecting parasitized C. capitata larvae and pupae exposed to EPNs with or without infection symptoms. The parasitoid's susceptibility period to EPNs was determined by applying them to C. capitata larvae at different days post-parasitism. Subsequently, adult parasitoids exposed to EPNs were kept in cages to assess sublethal effects of infection on insect physiology. Lastly, choice tests were conducted by offering previously infected and healthy C. capitata larvae to individual D. longicaudata females to determine host preference. Results showed that EPN-infected hosts impaired D. longicaudata development. However, parasitoid susceptibility to entomopathogens occurs only during the larval stage, as the puparium acts as a natural barrier with no impact on adult emergence. Additionally, the parasitoid preferred healthy larvae over infected ones, and no D. longicaudata eggs were found in infected hosts. Regarding sublethal effects, EPNs did not affect Net reproductive rate (R0), Intrinsic rate of increase (r), Finite rate of increase (λ), but increased Mean generation time (T) and Specific fertility rate (mx) of the subsequent generation of D. longicaudata parasitoids. Based on these findings, both biocontrol agents can be used effectively in fruit fly regulation provided that parasitoid release and EPN application occur sequentially and at appropriate times.