Interactions between entomopathogenic fungi and Tamarixia radiata (Hymenoptera: Eulophidae) in Diaphorina citri (Hemiptera: Liviidae) populations under laboratory conditions

Abstract

Biological control of Diaphorina citri (Kuwayama) using the parasitoid Tamarixia radiata (Waterston) or entomopathogenic fungi has been attempted, but there have been few published studies on their potential interactions when used together. We studied the effect of prior residency time on the outcomes of interactions between T. radiata and the fungal pathogens Beauveria bassiana and Metarhizium anisopliae in D. citri nymphs. In the first experiment, nymphs infected with fungi were exposed to the parasitoid after 0, 24 and 72 h. Next, nymphs with parasitoids at different developmental stages (eggs, larvae or pupae) were exposed to fungal inoculation. The greatest proportion of fungus-infected nymphs occurred when they were inoculated 72 h prior to parasitoid exposure. The lowest parasitism rate occurred in nymphs that had been infected by fungi 72 h prior to parasitoid exposure. The number of nymphs used for host-feeding by the parasitoid was similar, regardless of how advanced the fungal infection was. When fungal inoculations were made to parasitized nymphs with different developmental stages of the parasitoid, the greatest proportion becoming infected occurred in nymphs with parasitoid eggs. The overall longevity of adult parasitoids emerging from control and fungal-infected treatments was similar; however, the longevity of adult parasitoids emerging from nymphs which had been inoculated with parasitoid larvae were lowest, with the greatest effect observed for the M. anisopliae isolate. The ecological importance and practical recommendations derived from our results are discussed.