Unusual Behavior of Xylosandrus compactus (Coleoptera: Scolytinae) on Carob Trees in a Mediterranean Environment

Abstract

Xylosandrus compactus (Eichhoff), commonly known as the black twig borer, was reported in Sicily (Italy) at the end of 2016, infesting Carob tree (Ceratonia siliqua L.) twigs, large branches, and trunks. Previous research indicated that X. compactus attacks only small twigs and branches, not large branches and tree trunks. This unusual behavior was monitored through the two following years in five sites in Ragusa province (Sicily, Italy). For each of the monitored sites, the diameter of the infested trunks and branches was recorded. Samples of branches and trunks presenting galleries were removed from the trees and analyzed in the laboratory. Xylosandrus compactus occurred on branches of all monitored trees, while the percentage of infested trunks of carob trees ranged from 60% to 80%. Inside the infested galleries, all biological stages of X. compactus were found. Infestations were also recorded on trunks and branches with diameters greater than 80 cm and 30 cm, respectively. The mean number of X. compactus specimens inside the galleries was recorded and gallery shape was described. Unordinary behaviors, like the one described here for the first time, can affect the current efficiency of management recommendations.