The effects of floral nectar, extrafloral nectar and hemipteran honeydew on the fitness of Tamarixia radiata (Hymenoptera: Eulophidae), a parasitoid of Diaphorina citri

Abstract

Tamarixia radiata parasitizes nymphs of Diaphorina citri, a global citrus pest that vectors a bacterium that causes a lethal citrus disease, huanglongbing. The effects of four species of potted flowering native California plants, potted flowering buckwheat (Fagopyrum esculentum) and Euphorbia marginata (both non-native), honeydew from D. citri and Coccus hesperidum, cut flowers from lemon and orange trees, 50% honey-water, and water only on the longevity, survivorship and reproduction of T. radiata was investigated in the laboratory. Fecundity was measured by counting egg load of parasitoid cohorts ~15 h of age at time of set up and those that were removed for dissection from test arenas at 1, 6, and 18 days after introduction, or at time of death. Maximum survival of female T. radiata was 34 days on honey-water. Survival on honey-water, buckwheat and C. hesperidum honeydew was statistically equivalent, and these three food treatments significantly enhanced parasitoid survival when compared with all remaining food treatments. Female T. radiata fed on D. citri honeydew survived an average of 5 days, which was 3 days longer, on average, than those provided with water only. Parasitoid egg load significantly decreased with increasing days alive, thereby demonstrating the synovigenic nature of T. radiata. Parasitoids that fed on buckwheat flowers and died from natural causes had, on average, 5 more mature eggs in their ovaries at time of death when compared to parasitoids that died when provided access to other experimental sugar sources that were tested. These results suggest that buckwheat may be a useful insectary plant in citrus orchards that could enhance the efficacy of T. radiata against D. citri.