Effects of sugars on the gustatory response, longevity and realized fecundity of the egg parasitoid Trissolcus basalis

Parasitoids are widely used as biological control agents to manage insect pest populations in greenhouses. To meet their energetic and nutritional requirements, adult parasitoids consume carbohydrate-rich sources such as (extra-)floral nectar and honeydew. However, these sugar sources are often scarce or even absent in greenhouses, compromising the effectiveness of parasitoids as biological control agents. To remedy this, artificial sugar solutions can be provided to sustain parasitoid populations. To develop an artificial sugar solution that supports parasitoids, proper selection of sugars is critical. In this study, we investigated the innate gustatory response and survival of the egg parasitoid Trissolcus basalis (Wollaston) on eight plant- and/or insect-derived sugars (fructose, glucose, maltose, mannose, melezitose, rhamnose, sucrose and trehalose). Our results show that T. basalis can consume a wide range of sugars and survive on them. Five sugars (sucrose, fructose, maltose, melezitose and trehalose) increased its longevity more than seven-fold compared to the water control. For two sugars, sucrose and trehalose, the parasitoid's realized fecundity was monitored after various time periods during which the parasitoids were fed with the sugars (1 day, 1 week, 2 weeks, and 3 weeks). The results indicate a prolonged period of parasitism compared to the water control because of a longer lifespan when fed on the sugars. Altogether, our findings provide valuable insights for the development of an artificial sugar solution that supports the performance of T. basalis, potentially enhancing the biological control of important pest species such as Nezara viridula (Linnaeus).