Halyomorpha halys (Hemiptera: Pentatomidae) on kiwifruit in Northern Italy: phenology, infestation and natural enemies assessment

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), is an Asian invasive plant-feeding insect and an emerging kiwifruit pest. Knowledge about the BMSB dynamics and damage to kiwifruit outside the bug native range is scarce. This two-year study was aimed at describing phenology and infestation dynamics of BMSB in green-fleshed and yellow-fleshed kiwifruits. Natural enemies were investigated as well. Field surveys were performed weekly in two sites in Northern Italy by pheromone-baited traps and visual samplings, from early Spring to mid-Autumn. All BMSB life stages were collected and kept under observation to assess occurrence of parasitoids. A sample of fruit was dissected weekly to detect BMSB feeding injuries. In 2018-2019, BMSB was found throughout the growing season with two generations per year with a large overlapping of all life stages. Pheromone-baited traps and visual samplings gave consistent results and can be both considered effective sampling methods on kiwifruit. Fruit injuries were significantly related to kiwifruit development stage, weekly captures of BMSBs by traps and cultivar. Several BMSB egg masses were found on kiwifruit leaves. Anastatus bifasciatus Geoffroy, a native egg parasitoid with Palearctic distribution, emerged from 20.14% of eggs in 2018 but the percent parasitism dropped to 0.47% in 2019. In both years, other natural enemies were found exerting negligible pressure on BMSB populations. The determination of reliable economic thresholds for BMSB on kiwifruit is urgently needed to develop a robust and sustainable IPM strategy, and this study provides data towards that direction.