The green shield bug, Palomena prasina, and the red-legged shield bug, Pentatoma rufipes, two secondary pests of French hazelnuts

Since 2015, the number of hazelnuts damaged by insects in France has increased exponentially. Palomena prasina, Pentatoma rufipes (Hemiptera: Pentatomidae), and Gonocerus acuteangulatus (Hem.: Coreidae) are common insect species on hazel trees. In France, their pest status is unclear, and consequently limited data are available on their impact on French hazelnut cultivars. In 2016 and 2017, bugs were collected in orchards, and in 2018, specimens were isolated from hazelnut branches in net sleeve bags at different developmental stages throughout the season. At harvest, nuts shells were removed, and symptoms of feeding analyzed. Pentatoma rufipes, Pa. prasina, and G. acuteangulatus represented 34, 28, and 6%, respectively, of all bugs found in hazel orchards in 2016. In 2017, Pe. rufipes represented only 5%, while Pa. prasina was 48%, and G. acuteangulatus was 29%. While Pa. prasina and G. acuteangulatus are well-known as hazelnut pests in other areas, populations of Pe. rufipes are more erratic. Pentatoma rufipes caused the same amount of damage as Pa. prasina even though it penetrated deeper for feeding. Blank nuts, shrivelled, and corked kernels were the main injury symptoms. Brown spots caused by feeding mainly appeared during kernel expansion. However, white spots occurred when bugs fed on the kernels later in the season when they were fully developed. The study shows that Pa. prasina and Pe. rufipes are secondary hazelnut pests and need to be carefully monitored.