Coraebus undatus: an emerging pest in Sardinian cork oak forests

Abstract: Coraebus undatus (Fabricius) (Coleoptera: Buprestidae) is considered as a major
concern for cork production in Mediterranean regions. Larvae feed on the phellogen layer and excavate long galleries that are gradually incorporated into the cork layer as cork grows.
Infested cork shows a change in physical and mechanical characteristics, with a considerable
reduction in quality. In Sardinia (Italy), infestations of C. undatus have been recorded only
sporadically, but since 2016 damaged cork planks have dramatically increased in the northeastern part of the island. This work assessed the real threat of C. undatus to cork production in Sardinia by evaluating the distribution area of the infestations, the pest season phenology, and the dynamics of attacks between two debarking seasons (period 2011-2021). The temporal dynamics of C. undatus attacks was estimated by observing cork strips and dating the feeding galleries based on their positions between annual cork-rings. Based on our observations, attacks of C. undatus were concentrated in the cork oak forests closest to the industrial cork storage areas. Infestations decreased moving away from this focus of infestation to reach near-zero levels at 2 km in the northwest direction and 10 km in the southeast direction. The frequency of C. undatus attacks were relatively low in 2011-2015, increased exponentially from 2016 until 2019, and decreased dramatically afterwards. The flight curve estimated in 2021 on the basis of trap catches, showed the presence of adults starting from the first week of July, a peak at the second half of July, and the end of the flight at the end of August. In 2022, after placing the traps in mid-July, a peak likely occurred in the second decade of July, followed by a gradual decline and the end of adult flight in mid-August. The findings of this preliminary study need to be confirmed by multi-year observations.