Hyperparasitoids impact efficacy of biological control of Metcalfa pruinosa in Italy
Metcalfa pruinosa (Hemiptera, Flatidae) is a North American polyphagous planthopper that has become a pest in Europe since its introduction in the late 1970s. Neodryinus typhlocybae (Hymenoptera: Dryinidae, EPPO Classical BCA (PM 6/3)) has been introduced into the EPPO region (e.g. France, Italy, Slovenia, Switzerland) as a classical biological control agent for M. pruinosa. After almost 40 years, N. typhlocybae has established in most regions of Italy and achieves a satisfactory level of control. However, recently there have been reports of M. pruinosa infesting cultivated and semi-natural areas in north-eastern Italy prompting an assessment of the possible causes for the loss of efficacy of the biocontrol agent N. typhlocybae. In a two-year study, the mortality of N. typhlocybae cocoons was investigated. Over 4800 cocoons were collected from 14 sites in north-eastern Italy. Of these, more than 70 % were dead due predation and hyperparasitism. Nine hyperparasitoid species were identified, with the native Pachyneuron muscarum (Hymenoptera: Pteromalidae) and the North American Cheiloneurus swezeyi (Hymenoptera: Chalcidoidea) emerging as dominant species. C. swezeyi, reported for the first time in Europe, is known as a primary antagonist of N. typhlocybae in its country of origin. The specificity of C. swezeyi raises concerns about the long-term efficacy of N. typhlocybae as a biological control agent of M. pruinosa.
Sources
Mazzon L, Falasco M, Guerrieri E, Martinez-Sanudo I, Maretto L, Pozzebon A, Colombari F (2025) Presence of native and introduced hyperparasitoids raises concerns for the biocontrol of the planthopper Metcalfa pruinosa in Europe. Biological Control, 211,105914. https://doi.org/10.1016/j.biocontrol.2025.105914