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

Abstract

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.