|Neser, Stefan - PLT PRO INSTIT, S.AFRICA|
|Westhuizen, Liame - PLT PRO INSTIT, S.AFRICA|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2008
Publication Date: June 1, 2010
Citation: Balciunas, J.K., Neser, S., Westhuizen, L.V., Mehelis, C.N. 2010. Laboratory Host Range of Parafreutreta regalis (Diptera: Tephritidae), a candidate agent for Biological Control of Cape ivy. Environmental Entomology. 39(3):841-848. Interpretive Summary: Invasive weeds degrade natural areas, cause billions dollars worth of losses in agriculture, and weed control accounts for more than half the pesticides used in the United States. Classical biological control – the release of carefully selected and tested insects and other natural enemies from the native home of the weed – is a proven strategy for reducing the impacts of invasive weeds, and reducing the use of herbicides. To avoid direct impacts on crops and beneficial native plants, prior to release, the intended agents are screened to assure that they are host-specific, and will not damage non-targets. This paper presents the results of our tests to determine if a gall fly being considered for use as biological control agent for Cape-ivy is safe enough for release in California, where this vine is a very serious weed. Our tests demonstrate that this fly is host specific to Cape-ivy, and is, therefore, safe for release. If permission for release is granted, this fly could prove to be a valuable management tool for controlling Cape-ivy.
Technical Abstract: Cape-ivy (Delairea odorata Lamaire) is an ornamental vine that has escaped into natural areas in many countries and become a serious pest. It is native to the eastern part of South Africa, and surveys there located several potential biological control agents for this weed. One of these is Parafreutreta regalis Munro, a tephritid fly that causes large galls to form on the stems of the vine. In a collaborative effort, we began to evaluate, in both California and South Africa, the host range of this fly. Between the two locations, we tested 88 plant species to see if, after being exposed to 4 pairs of flies for a week, any galls would develop on them. No galls were formed on any of the test species, although an average of six galls developed on the Cape-ivy controls. We also tested to see if P. regalis showed any preference for either of the two varieties of Cape-ivy. There was no significant difference between the numbers of galls forming on the stipulate or astipulate varieties. Our tests indicate that this fly is essentially mono-specific. Earlier research had demonstrated that P. regalis galls cause a significant reduction in the height and non-gall biomass of Cape-ivy. A petition is being prepared to initiate the process of obtaining permission to release P. regalis in California to control the Cape-ivy infestations there.