Honeydew associated with four common crop aphid species increases longevity of the parasitoid wasp, Bracon cephi (Hymenoptera: Braconidae)

Authors: Rand, Tatyana; Senior, Laura

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2023
Publication Date: 5/22/2023
Citation: Rand, T.A., Senior, L. 2023. Honeydew associated with four common crop aphid species increases longevity of the parasitoid wasp, Bracon cephi (Hymenoptera: Braconidae). The Canadian Entomologist. 155:1-8. Article e20. https://doi.org/10.4039/tce.2023.5.
DOI: https://doi.org/10.4039/tce.2023.5

Interpretive Summary: The absence of sugar resources in simplified agricultural landscapes is thought to be a major factor limiting the success of biological control of crop pests. Restoring vegetation complexity within these landscapes has thus become a major focus of conservation biological control efforts, with a traditional emphasis on bolstering floral resources. However, aphid honeydew can also provide sugar resources that are seldom considered in the context of conservation biological control. Here we present results from a lab experiment demonstrating that feeding on honeydew produced by common crop aphids (in wheat, pea and canola) dramatically increases the longevity (2-3 fold) of biocontrol wasps attacking the wheat stem sawfly, the dominant pest of wheat in the northern Great Plains. The results suggest that aphids occurring in crops at sub-economic levels may provide critical sugar resources to sawfly parasitoids, enhancing their potential efficacy, and re-enforcing Integrated Pest Management recommendations regarding the avoidance prophylactic pesticide applications. More generally, the results suggest that honeydew provisioning is likely an important mechanism underlying the benefits of crop diversification to support biological control that merits further research. Increasing the efficacy of biological control of the wheat stem sawfly is critical to reducing the economic impacts of this pest for wheat producers in the Northern Plains.

Technical Abstract: The absence of sugar resources can be an important factor in limiting the success of parasitoids as biological control agents. Restoring vegetation complexity within agricultural landscapes has thus become a major focus of conservation biological control efforts, with a traditional emphasis on nectar resources. Aphid honeydew is also an important source of sugars that is infrequently considered. We carried out a laboratory experiment to examine the potential effects of honeydew from six different aphid species by crop species combinations on the longevity of Bracon cephi Gahan (Hymenoptera: Braconidae), the most important biological control of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), a major pest of wheat in the northern Great Plains of North America. The benefits of honeydew for parasitoid longevity varied significantly among different aphid and crop species, illustrating the complexity of these interactions. However, honeydew produced by four aphid species commonly found in wheat, pea, and canola crops significantly increased the longevity (by two- to threefold) of the parasitoid. The study suggests that honeydew provisioning could be an important mechanism underlying the benefits of crop diversification to support biological control that merits further research.