Biology and monitoring of <i>Dryocosmus kuriphilus</i> on <i>Castanea sativa</i> in Southern Italy

Abstract

The cynipid gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is an invasive wasp in Europe and is one of the major pests of chestnuts worldwide. An investigation of this cynipid was started in Campania, Southern Italy, in 2008, with the aim of providing guidelines for its sustainable control. The number of larvae/gall increased in the second year of colonization relative to the first one but thereafter decreased in the third year of colonization, whereas the volume of the galls after the initial increase in the second year of colonization became stable. Adult emergence generally peaked between the middle of June and July. The only reliable method for assessing the presence of the pest at its earliest stage was through dissecting the buds because oviposition scars on the buds tended to disappear during the winter. Yellow traps were shown to be an effective method for assessing the emergence of cynipid adults and could potentially be used to time chemical applications in those cases in which this control method is feasible. No correlation was recorded between the relative durations of the final stages (pupae, pharate adults and emergence). Possible control strategies for this invasive pest are discussed.