Biology and ecology of Brazilian elodea (Egeria densa) and its specific herbivore Hydrellia sp in Argentina

Authors: CABRERA WALSH, GUILLERMO - South American Biological Control Lab(SABCL); DALTO, Y.MAGALI - National Atomic Energy Commission; MATTIOLI, FEDERICO - Monsanto Corporation; Carruthers, Raymond; Anderson, Lars

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2012
Publication Date: 8/4/2013
Citation: Cabrera Walsh, G., Dalto, Y., Mattioli, F., Carruthers, R.I., Anderson, L.W. 2013. Biology and ecology of Brazilian elodea (Egeria densa) and its specific herbivore Hydrellia sp in Argentina. Biocontrol. DOI 10.1007/s10526-012-9475-x.

Interpretive Summary: Egeria densa is a submerged plant of South American origin that has become noxious in 38 U.S. states as well as several other countries. It crowds out native plant species and hinders water use in several manners. An aquatic fly of the genus Hydrellia sp. 1, was found to attack Egeria throughout its distribution in Argentina. It can defoliate the plant, both in the laboratory and in the field in its native range. In the field Hydrellia sp. 1 was collected only on E. densa, but in the laboratory it also developed on two other Hydrocharitaceae species, Egeria naias, and Elodea callitrichoides, and marginally on Naias guadalupensis. However, significant oviposition and feeding was only obtained on its natural host, and to a lesser degree on E. naias. Field studies indicate Hydrellia sp. 1 is present in the field year round, except if the host plant is inaccessible for prolonged periods, as when it is covered by floating macrophytes or prostrate due to climatic conditions. Its type of damage and geographical distribution suggest that this species may be a good candidate for the biocontrol of E. densa in the U.S.

Technical Abstract: Egeria densa is a submerged plant of South American origin that has become noxious in 38 U.S. states as well as several other countries. It crowds out native plant species and hinders water use in several manners. The leaf mining shore fly Hydrellia sp. 1, found to attack Egeria throughout its distribution in Argentina, has been reared successfully in the laboratory, and tested for damage levels and host specificity on 25 plant species. It can defoliate the plant, both in the laboratory and in the field in its native range. In the field Hydrellia sp. 1 was collected only on E. densa, but in the laboratory it also developed on two other Hydrocharitaceae species, Egeria naias, and Elodea callitrichoides, and marginally on Naias guadalupensis. However, significant oviposition and feeding was only obtained on its natural host, and to a lesser degree on E. naias. Field studies indicate Hydrellia sp. 1 is present in the field year round, except if the host plant is inaccessible for prolonged periods, as when it is covered by floating macrophytes or prostrate due to climatic conditions. This species may be a good candidate for the biocontrol of E. densa, although more species in its plant family, not found in South America, should be tested.