Location: Invasive Species and Pollinator HealthTitle: Complete development on Elodea canadensis (Hydrocharitaceae) eliminates Hydrellia egeriae (Diptera, Ephydridae) as a candidate biological control agent of Egeria densa (Hydrocharitaceae) in the U.S.A
Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2018
Publication Date: 1/6/2019
Citation: Pratt, P.D., Herr, J.C., Carruthers, R., Walsh, G. 2019. Complete development on Elodea canadensis (Hydrocharitaceae) eliminates Hydrellia egeriae (Diptera, Ephydridae) as a candidate biological control agent of Egeria densa (Hydrocharitaceae) in the U.S.A. Biocontrol Science and Technology. 29(4):405-409. https://doi.org/10.1080/09583157.2018.1564245.
Interpretive Summary: California waterways are critical for the wellbeing of the public and food production. The Brazilian waterweed is not native to the USA but readily spreads in California's lakes and rivers. The exotic plant grows below the water surface, where it interferes with water movement and plugs irrigation canals. A very small fly, with the scientific name Hydrellia egeriae, attacks Brazilian waterweed in South America and was studied to determine if it could be used to help control Bazilian waterweed in California. The objective of this study was to determine if the fly would feed on Elodea canadensis, a native plant that looks similar to Brazilian waterweed. Scientists held the fly with the native plant and learned that the fly would lay eggs and complete development on Elodea. These data indicate that the fly poses a risk to the native plant tested and isn't suitable for using in California or other areas of the USA where Elodea is native.
Technical Abstract: The ephydrid fly Hydrellia egeriae was evaluated under quarantine conditions as a biological control agent of the invasive aquatic weed Egeria densa in California, U.S.A. The objective of this study was to test the fly’s feeding preference when held with the North American native Elodea canadensis, an important benchmark species. No choice testing revealed that H. egeriae can complete development when held with E. canadensis and choice testing indicated the fly presents little oviposition discrimination between E. densa and E. canadensis. It is concluded that the host range of H. egeriae is too broad for consideration as a biological control agent of E. densa in the U.S.A.