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ViewAttendees 10

P-IE

10-Minute Paper

10-min: P-IE, Biocontrol

Reintegrating nectar resources in a semi-arid grassland to benefit braconid parasitoids

On-Demand
On-Demand
The Northern Great Plains (NGP) of North America is a semi-arid grassland dominated by intensive agricultural practices, primarily the production of cereal crops. Current land use regimes suppress biotic diversity, sacrificing valuable ecosystem services like biological control of crop pests. The pest wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), costs NGP wheat growers $350 million annually. Two parasitoids of WSS, Bracon lissogaster Muesebeck and Bracon cephi Gahan (Hymenoptera: Braconidae), show promise as conservation biological control agents. These parasitoids experience increased longevity, egg load, and volume when provided carbohydrate-rich food resources. To assess availability of floral nectar to parasitoids from wildland flowering species, we conducted surveys in a 12-ha relict native prairie area near Havre, Montana, USA, during summer of 2019 and 2020. Our site is otherwise similar to non-crop, previously disturbed areas near dryland wheat production. Our results show high abundance of wildland flowering species during 2019, totalling 29,122 plants and 53 different species. Previous documentation reports that cultivating wildland and other flowering species near host crops increases the benefits of biological control agents in agricultural systems. Field trials were conducted for the legume cowpea (Vigna unguiculata L. Walpers) as a potential cover crop in Montana. Our results show that pollinators and natural enemies were attracted to this legume's extrafloral nectaries. Bolstering these parasitoids with nectar sources such as cowpea and nearby wildflower areas could increase biotic diversity and reduce WSS populations. To our knowledge, enhancing native biological controls to directly suppress WSS has never been implemented.