The brown marmorated stink bug (BMSB), Halyomorpha halys Stål (Hemiptera: Pentatomidae), is an invasive species, nowadays worldwide listed among the key agricultural pests. Native of China, Japan and Korea, BMSB is a very polyphagous stink bug with an increasing list of recorded host plants (Hamilton et al., 2018). When it becomes established, it represents a major threat for several commercial crops such as apple (Bergh et al., 2019), hazelnuts (Hedstrom et al., 2014), kiwi (Chen et al., 2020, pears and peaches (Nielsen & Hamilton, 2009).Brown marmorated stink bug was first recorded in Italy in 2012, and since then it rapidly spread reaching high densities in the north of the country (Maistrello et al., 2018;Malek et al., 2019). In this area, olive trees (Olea europaea L.) produce modest quantities of high-quality extra virgin olive oil for both local market and export.Previous observations suggested that the damage of BMSB feeding activity on olive can be severe (D'Ascenzo et al., 2020;Damos et al., 2019) and that it may be associated with early drop (Minuto, 2021). Thus, the objective of this study was to examine the effect of BMSB feeding activity on developing olives by assessing