Attack strategy of the bark beetle Tomicus destruens (Wollaston 1865) (Coleoptera: Scolytidae) on Aleppo pine in semi-arid areas (Algeria, Djelta)

Females of Tomicus destruens cause serious injury to Aleppo pines when building their egg galleries under the bark. Group attacks on pine trees by the adult beetles result in tree deaths and consequently pine forest decay. A study of the preferred sites for attacks demonstrated variability between individual trees. Females prefer trees at the northern slopes of the hills. T destruens breeds there more actively and gives more abundant progeny. While on the northern slopes of the hills, the female's choice the bark exposed to the south to bore their galleries. Additionally, both tree trunk diameter and the thickness of the bark were found to be critical factors for selection. Among other factors influencing Tomicus destruens attacks is the age of individual trees. Counting the number of egg galleries and measuring their lengths revealed a strong negative correlation between the density of infestation and length of the galleries. Intraspecific competition within T destruens was demonstrated also. Reproductive success is controlled by the density of the galleries, which in turn is determined by the bark surface available for breeding.