Increasing entomopathogenic nematode biodiversity reduces efficacy against the Caribbean fruit fly Anastrepha suspensa: interaction with the parasitoid Diachasmimorpha longicaudata

Abstract

Entomopathogenic nematode (EPN) species richness merits studies towards making rational decisions for effective management of Caribfly, Anastrepha suspensa (Loew) in southern Florida. Competition for Caribfly and efficacies of EPN biodiversity were examined under laboratory conditions. Similar EPN species treatments to Caribfly-infested fruits, periodically obtained from the ground in groves which were also infested by the parasitoid Diachasmimorpha longicaudata Ashmead (Braconidae), were studied in a series of field trials. Treatments with individual EPN species and their mixtures caused similar mortalities of Caribfly larvae, though the various EPN species competed for larvae in multiple-species treatments. Laboratory trials showed that mortalities of EPN-treated Caribfly pupae were mostly inversely related to EPN diversity. In the field, population densities of emerging adult Caribfly increased with increasing number of EPN species combined in treatments. Thus, single-EPN species treatments proved to be more effective for the management of fruit-to-soil stages of Caribfly. Relative to controls, the proportions of surviving adult Caribfly observed in EPN treatments with Heterorhabditis bacteriophora (exotic in Florida), Steinernema feltiae (exotic EPN) and Heterorhabditis indica (the endemic species) in field plots were 22.5 ± 6, 45 ± 13 and 47 ± 13%, respectively. Number of emerging D. longicaudata in each of EPN species treatments was similar to that observed in control, suggesting that none of the EPN species significantly affected the emergence of D. longicaudata, a parasitoid of Caribfly. Heterorhabditis bacteriophora will be more promising, with insignificant side effects on D. longicaudata in Caribfly-integrated pest management.