Biological control ofRhamnus cathartica: is it feasible? A review of work done in 2002–2012

Abstract

AbstractRhamnus cathartica(common buckthorn) is a shrub (or small tree) of Eurasian origin, which has become invasive in North America. Internal feeders and sap suckers were prioritized for biological control from over 30 specialized insects identified from the target plant in its native European range. Five leaf‐feeding moths were also considered for further investigations. Field observations and preliminary host range tests with the stem‐boring beetleOberea pedemontana, the root‐boring mothSynanthedon stomoxiformis, the shoot‐tip‐boring mothSorhagenia janiszewskaeand the leaf‐feeding mothsAncylis apicella,A. unculana,Triphosa dubitata,Philereme transversataandP. vetulataconfirmed that all of these species were lacking host specificity in no‐choice conditions. Choice oviposition tests carried out with most of the prioritized species to assess their ecological host range yielded unreliable results. Three psyllids,Trichochermes walkeri,Cacopsylla rhamnicollaandTrioza rhamniare promising in terms of host specificity, but are infected with the plant disease ‘CandidatusPhytoplasma rhamni’. Fruit‐ or seed‐feeding insects may present the best potential for biological control of buckthorn in directly reducing seed set and thus seedling establishment. However, it was not possible to obtain adult fruiting trees of native North AmericanRhamnusspecies for testing. It is concluded that there are no promising arthropod agents based on what is known to date. Pathogens could offer new opportunities for biological control ofR. catharticain North America.