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Title: Sugar concentration and timing of feeding affect feeding characteristics and survival of a parasitic wasp

Author
item Williams, Livy
item DESCHODT, PAULINE - Montpellier Supagro – International Center For High Education In Agricultural Sciences
item POINTURIER, OLIVIA - Montpellier Supagro – International Center For High Education In Agricultural Sciences
item KRIS, WYCKHUYS - International Center For Tropical Agriculture (CIAT)

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2015
Publication Date: 5/27/2015
Citation: Williams Iii, L.H., Deschodt, P., Pointurier, O., Kris, W. 2015. Sugar concentration and timing of feeding affect feeding characteristics and survival of a parasitic wasp. Journal of Insect Physiology. 79:10-18.

Interpretive Summary: Many beneficial insects that parasitize agricultural crop pests rely on food sources for survival. Nectar and other sugar-based substances serve this need, but are sometimes unavailable at the time and place where beneficial insects are foraging. Therefore, the value of even a single meal is crucial for survival. Psyttalia lounsburyi is a parasitic insect which attacks the olive fruit fly, the major pest of olives in the U.S. In order to improve our understanding of the nutritional needs of this beneficial insect and to enhance its survival we evaluated the effect of a single sugar meal on the feeding characteristics and longevity of the insects. We measured the time spent feeding, amount of food ingested, sugar consumption, caloric content, and survival time of wasps provided with three different concentrations of sucrose at four different ages (=starvation levels). Our results showed that survival time was affected by sugar concentration and age of the beneficial insect. Feeding on sugar reduced the risk of starving to death, and longest time spent feeding was observed for the highest sucrose concentrations and oldest insects. The amount of sugar ingested and caloric content increased, up to a point, with sugar concentration. Our findings suggest that the beneficial insect derives greatest benefit from an intermediate concentration of sucrose at 2 or 3 days of age. Our study emphasizes the importance of finding balance between increasing longevity and limiting time spent feeding, and concomitant uptake of nutrients, that is fundamental for survival of this insect in agricultural fields.

Technical Abstract: The availability of food sources is critical for parasitoid survival, especially for those that do not host-feed, or in agroecosystems where nectar and honeydew are sometimes spatially and temporally scarce. Therefore, the value of even a single meal can be crucial for survival. Psyttalia lounsburyi is a parasitoid, and biological control agent, of the olive fruit fly, Bactrocera oleae. In order to improve our understanding of the nutritional needs of P. lounsburyi and to enhance its survival we evaluated the effect of a single sucrose meal on the longevity of female wasps. We measured the duration of feeding, volume ingested, sucrose consumption, energy content, and longevity of wasps provided with different concentrations of sucrose (0.5, 1, and 2 M) at different times after emergence (0, 1, 2 or 3 days after emergence). Our results showed that longevity was significantly affected by the concentration and the timing of feeding. Feeding on sucrose reduced the risk of starving to death from 32.3 to 95.4% compared to water-only controls. The longest duration of feeding was observed for the highest sucrose concentrations and oldest wasps. The amount of sugar ingested and energy uptake increased with sugar concentration. Our results suggest that P. lounsburyi wasps derive greatest benefit from the intermediate concentration (1 M) of sucrose 2 or 3 days after emergence. Our study emphasizes the importance of finding balance between increasing longevity and limiting the duration of feeding, and concomitant uptake of nutrients, that is fundamental for survival of the wasp in nature.