Flowering plants serve nutritional needs of Ascogaster quadridentata (Hymenoptera: Braconidae), a key parasitoid of codling moth

The codling moth Cydia pomonella (Linnaeus, 1758) (Lepidoptera: Tortricidae) is the major pome fruit pest
worldwide, causing direct fruit damage and significant yield losses. The egg-larval koinobiont parasitoid Ascogaster
quadridentata (Wesmael, 1835) (Hymenoptera: Braconidae) contributes to the natural regulation of codling moth
populations. Similar to many other parasitoid Hymenoptera, adult A. quadridentata could also benefit from high
plant diversity in orchards if it fed on flowers. However, its particular nutritional requirements are rather unknown.
For the first time, possible effects of sugar or flower resources on the performance of this parasitoid were studied in
laboratory experiments. Wasps fed with highly concentrated sucrose or glucose solutions lived three to five times
longer than starving individuals. Trehalose also supported survival, whereas mannose was not suitable. Parasitoids
were able to exploit sugar solutions of low (10%) to high (64%) concentrations. Survival was more than twice as long
when flowers of buckwheat, coriander, wild carrot, and parsnip were offered. Parasitism capacity was strongly
linked to female longevity and thus to adequate nutrition of adults. Under the prevailing experimental conditions,
performance of wasps was three times higher on flower diet compared to that of starved wasps. Suitable plants
flowering during the activity period of A. quadridentata might therefore improve the ecosystem service provided by
this important codling moth parasitoid and help increasing functional biodiversity in orchards.