Submitted to: Program Review of Interagency Bemisia Classical Biocontrol Program in the U.S.
Publication Type: Book / Chapter
Publication Acceptance Date: 1/19/2006
Publication Date: 3/26/2008
Citation: Hoelmer, K.A., Schuster, D.J., Ciomperlik, M.A. 2008. Indigenous parasitoids of Bemisia in the United States and potential for non-target impacts of exotic parasitoid introductions. In: Gould, J., Hoelmer, K., Goolsby, J., editors. Classical Biological Control of Bemisia tabaci in the United States: a Review of Interagency Research and Implementation. Vol. 4, Progress in Biological Control, H.M.T. Hokkanen (series ed.). The Netherlands: Springer, Dordrecht, p. 307-324. Interpretive Summary: Before introducing exotic biological control agents against pests, it is important to know which natural enemies are already present in the area where introductions are anticipated. Surveys to document the presence and identities of native natural enemies that have adapted to a newly-introduced pest species are therefore vital in any classical biological control program before any new agents are introduced. Regional surveys were conducted prior to introducing new agents against sweetpotato (=silverleaf) whitefly in the United States. In addition, surveys of selected native whiteflies were carried out during and after the conclusion of exotic agent releases specifically in the Imperial Valley of California. These laid the necessary groundwork for long term monitoring that will allow scientists to detect shifts in host specificity of newly-introduced natural enemies, if any should occur over time. No such non-target impacts were detected in surveys conducted during the first three years after releases.
Technical Abstract: Prior to the introduction of any new and non-indigenous biological control agents it is essential to know which natural enemies are already present in the area where introductions are anticipated. Without this knowledge it is impossible to determine whether the establishment of an agent resulted from a deliberate introduction or from an unintended and previously unknown introduction. Thus, surveys to document the presence of native natural enemies that have adapted or switched to a newly-introduced pest species and document their species composition are vital in any classical biological control program before any new agents are introduced. Such surveys were conducted prior to the introduction of non-indigenous agents against sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype 'B' (= silverleaf whitefly, B. argentifolii Bellows & Perring), in the United States. Survey groups in different regions developed their own procedures for surveys according to their local crops and other plants that were infested with whitefly. However, general survey procedures in each area involved the periodic collection of Bemisia-infested foliage samples from a wide range of crops, weeds, ornamentals, and other native plants. The greatest diversity of native parasitoid species was reported from surveys in Florida. Possibly this was a result of the very high diversity of whitefly species in Florida, which is frequently invaded by exotic species of whitefly, some of which may be the primary hosts of parasitoids that were reared in low numbers from B. tabaci. Only two or three species were responsible in any region for most of parasitism of B. tabaci. The host specificity of newly-introduced natural enemies was addressed in the Imperial Valley, CA, by incorporating surveys of selected indigenous whiteflies found in habitats where B. tabaci occurred during and following the conclusion of the release programs, laying the necessary groundwork for long-term monitoring of host shifts and nontarget impacts. As of the latest surveys in 2000-01 (California) and 2002-03 (Texas), the exotic species that were introduced have remained limited to their intended target, B. tabaci. Continued monitoring will be needed to demonstrate whether or not this remains the case over the long term.