Behavioral and ovipositional response of Diaeretiella rapae (Hymenoptera: Braconidae) to Rhopalosiphum padi and Brevicoryne brassicae in winter wheat and winter canola

Authors: FERGUSON, MARY - University Of Arkansas; GILES, KRISTOPHER - Oklahoma State University; Elliott, Norman - Norm; PAYTON, MARK - Oklahoma State University; ROYER, TOM - Oklahoma State University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2018
Publication Date: 12/1/2018
Citation: Ferguson, M.E., Giles, K.L., Elliott, N.C., Payton, M.E., Royer, T.A. 2018. Behavioral and ovipositional response of Diaeretiella rapae (Hymenoptera: Braconidae) to Rhopalosiphum padi and Brevicoryne brassicae in winter wheat and winter canola. Environmental Entomology. 47(6):1517-1524. https://doi.org/10.1093/ee/nvy151.
DOI: https://doi.org/10.1093/ee/nvy151

Interpretive Summary: Winter canola was introduced to Southern Great Plains hard red winter wheat growers to diversify the wheat cropping rotation and manage some difficult-to-control grassy weeds. Canola is host for several damaging aphid pests, including the cabbage aphid, the green peach aphid, and the turnip aphid. We compared the behavioral responses of D. rapae to volatile chemicals produced by the plant originating from two aphid/plant combinations: (wheat/bird cherry oat aphid and canola/cabbage aphid). Wasps that emerged naturally from mummies collected in wheat and canola had higher responses to plant and plant+aphid odors. Neither group responded odors from aphids alone. Odors from the combination of plant+aphid were most attractive. We attempted to further describe parasitoid/host/plant associations by comparing D. rapae that originated from either wheat or canola aphids on their ability to utilize canola and wheat aphids as hosts. Parasitism rates on canola-reared aphids were higher than on wheat-reared aphids and lowest when D. rapae was utilizing a novel host. Overall, our results indicate that D. rapae populations present in wheat and canola fields are likely to be preferentially associated with aphids in habitats consisting of canola and other crucifer vegetation. The significance of the research lies in the observation that there was minimal interaction of D. rapae among aphid hosts in the two crops, suggesting limited potential for enhancing biological control of aphids in wheat and canola by D. rapae having the two crops grown in close proximity.

Technical Abstract: Winter canola was introduced to Southern Great Plains hard red winter wheat growers to diversify the wheat cropping rotation and manage some difficult-to-control grassy weeds. Canola is host for several damaging aphid pests, including the cabbage aphid (Brevicoryne brassicae L., the green peach aphid Myzus persicae (Sulzer), and the turnip aphid Lipaphis pseudobrassicae (Davis) (Hemiptera: Aphididae). Two aphid parasitoids are active in this cropping landscape. Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae) is the predominant parasitoid in winter wheat and Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) is the predominant parasitoid in canola. We compared the behavioral responses of D. rapae that were excised from their original aphid host with those allowed to emerge normally to volatiles originating from two aphid/plant combinations: (wheat/bird cherry oat aphid and canola/cabbage aphid). Wasps that emerged naturally from mummies collected in wheat and canola had higher responses to plant and plant+aphid odors. Neither group responded odors from aphids alone. Odors from the combination of plant+aphid were most attractive. We attempted to further describe parasitoid/host/plant associations by comparing D. rapae that originated from either wheat or canola aphids on their ability to utilize canola and wheat aphids as hosts. Parasitism rates on canola-reared aphids were higher than on wheat-reared aphids and lowest when D. rapae was utilizing a novel host. Overall, our results indicate that D. rapae populations present in the wheat-canola landscape of the Southern Great Plains are likely to be preferentially associated with aphids in habitats consisting of canola and other crucifer vegetation.