Do floral resources benefit the herbivorous sawfly, Cephus cinctus, a major pest of wheat in North America?

Authors: Rand, Tatyana; Titus, Ellen; Waters, Debra

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2018
Publication Date: 4/1/2019
Citation: Rand, T.A., Titus, E.F., Waters, D.K. 2019. Do floral resources benefit the herbivorous sawfly, Cephus cinctus, a major pest of wheat in North America? Journal of Economic Entomology. 112(2):565-570. https://doi.org/10.1093/jee/toy408.
DOI: https://doi.org/10.1093/jee/toy408

Interpretive Summary: Developing flower resources for habitat management programs to promote biological control of crop pests requires carefully screening prospective flowers for their benefits not just for control agents, but also for targeted pest species. Here we examined the potential influence of access to various sugar sources on the wheat stem sawfly, Cephus cinctus, a major pest of wheat in the northern Great Plains of North America. We conducted a series of greenhouse studies to test whether access to a honey-sugar solution, three different flowering plant species, or aphid honeydew increased the number of days that sawflies lived, or the number of eggs they laid in wheat stems. Sawfly lived 1.18 - 1.25 times as long in treatments with flowering buckwheat (Fagopyrum esculentum), a common cover crop species, compared with controls. In contrast, there was no significant effect of the two additional floral species tested, canola (Brassica napus) and white mustard (Sinapis alba), or aphid (Myzus persicae) honeydew on the number of days sawflies lived. Access to buckwheat did not significantly increase the number of eggs laid by C. cinctus, suggesting that sugar feeding on this pant is unlikely to increase its impact as a pest. To our knowledge, this is the first published experimental evidence that feeding on flowers can increase the lifespan of the wheat stem sawfly. Our results suggest that screening prospective flowering plants that are being considered in conservation biological control programs to bolster wheat stem sawfly parasitoids, against the pest as well, will be an important precautionary measure in future work.

Technical Abstract: Effectively leveraging floral resources as part of habitat management programs to promote biological control of crop pests requires carefully screening prospective floral species for their suitability not just for natural enemies, but also for targeted pest species which may also benefit. Here we examined the potential influence of access to various sugar resources on Cephus cinctus, a major pest of wheat in the northern Great Plains of North America. We conducted a series of greenhouse studies to examine the effect of access to a honey-sucrose solution, three flowering plant species, and aphid honeydew, on the longevity and potential fecundity of C. cinctus. We found that C. cinctus female longevity increased significantly (with individuals living 1.18 - 1.25 times as long) in treatments with buckwheat (Fagopyrum esculentum) flowers compared with controls. In contrast, there was no significant effect of the two additional floral species tested, canola (Brassica napus) and white mustard (Sinapis alba), or aphid (Myzus persicae) honeydew on C. cinctus longevity. Access to buckwheat did not significantly increase the cumulative number of eggs laid by C. cinctus, suggesting that sugar feeding on this pant is unlikely to increase its impact as a pest. To our knowledge, this is the first published experimental evidence that access to floral resources can increase the adult lifespan of C. cinctus. The results re-inforce previous observations that sugar feeding may be common in Cephus spp. and other Cephidae. Our results suggest that screening prospective floral species being considered in conservation biological control programs to bolster C. cinctus parasitoids, against the pest as well, will be an important precautionary measure in future work.