Phloeotribus scarabaeoides (Bernard)
Taxonomic placing: Insecta, Holometabola, Coleoptera, Curculionidae, Scolytinae.
Common name Olive bark beetle.
Geographical distribution: Europe, North Africa and the Middle East.
Host plants: Olive and other Oleaceae, like Fraxinus, Ligustrum, Syringa and Phyllirea.
Morphology: Body of adult grey-brown or darker, about 2-2.5 mm in length, head in ventral position, elytra with many longitudinal stripes. Thorax punctated and with many short hairs, its middle third darker than the flanking parts, terminal segment of male antennae tridentate. Larvae yellow-whitish, with brown head, apodous, about 3 mm long..
Life history: In spring the adults start to bore galleries at the bases of young twigs of weakened trees or in broken branches and logs, and lay their eggs there. The emerging larvae excavate their own galleries, usually perpendicular to the maternal gallery. The pest prefers trees that stand in drier and shallow soil, which are usually weaker. It raises 3 annual generations. The commerce in infested olive logs aids the pest’s dispersal.
Economic importance: Severe infestations may reduce the number of flowers and olive fruits, and the resulting damage can reach 70% of the crop. Olive orchards may become completely unproductive within 5 years of such infestations. Tree survival in young groves may be endangered, and olive oil quality can be affected.
Management
Monitoring: The density of the galleries produced in young olive branches can be used to indicate severity of infestation. Decrease in olive yield can be expected when there are >3 pest galleries/meter branch.
Horticultural methods: Appropriate fertilization, pruning and the removal or burning of infested branches.
Chemical control: Treating logs with pesticides (like pyrethroids before the emergence of the adult beetles, which are attracted ethylene. Beetle numbers were reduced in an olive grove surrounded by a barrier of trap-trees that were sprayed with a mixture of ethylene and a pyrethroid. Ethylene can also be used in lure-and-trap control systems.
Biological control: The beetle is attacked by several bethylid, braconid, eurytomid and pteromalid endoparsitoids, whose abundance and controlling effects vary from year to year and from region to region. The dominant natural enemy is the pteromalid Cheiropachus quadrum (Fabricius), which can reduce pest populations by 30-50%. Natural enemies might be adversely affected by the application of pyrethroids.
References
Abul Fadl, H.A.A., Ibrahim, A.M.A., Afify, A.I. and Ahmed, M.M. 2010. Some ecological aspects of the olive bark borer, Phloeotribus scarabaeoides (Bern.) (Coleoptera: Scolytidae), and its parasitoids. Egyptian Journal of Biological Pest Control 20: 171-174.
Campos, M. and Lozano, C. 1994. Observations on the reproductive biology of two parasites of Hylesinus varius and Phloeotribus scarabaeoides (Col: Scolytidae): Cheiropachus quadrum (Hym: Pteromalidae) and Dendrosoter protuberans (Hym: Braconidae). Entomophaga 39: 51–59.
Gonzalez, R. and Campos, M. 1994. A preliminary study of the effect of attacks by Phloeotribus scarabaeoides (Bern.) (Coleoptera: Scolytidae) on the productivity of the olive tree (Olea europaea L.). Mitteilungen der Schweizerischen Entomologischen Gesellschaft 67: 67-75.
González, R. and Campos, M. 1995. A preliminary study on the use of trap-trees baited with ethylene for the integrated management of the olive beetle, Phloeotribus scarabaeoides (Bern.) (Col., Scolytidae). Journal of Applied Entomology 119: 601–605.
Lozano, C., Kidd, N.A.C. and Jervis, M.A. 1997. Effects of parasitoid spatial heterogeneity, sex ratio and mutual interference on the interaction between the olive bark beetle Phloeotribus scarabaeoides (Col., Scolytidae) and the pteromalid parasitoid Cheiropachus quadrum (Hym., Pteromalidae). Journal of Applied Entomology 121: 521-528.
Mendel, Z. 1986. Hymenopterous parasitoids of bark beetles [Scolytidae] in Israel: Host relation, host plant, abundance and seasonal history Entomophaga 31: 113-125.
Rodríguez, E., Campos, M., Sánchez Raya, A.J. and Peña, A. 2003. Effect of the combined treatment of insecticides and an attractant for the control of Phloeotribus scarabaeoides, a pest of Olea europea. Pest Management Science 59: 339-46.
Ruano, F., Campos, M., Sánchez-Raya, A.J. and Peña, A. 2010. Olive trees protected from the olive bark beetle, Phloeotribus scarabaeoides (Bernard 1788) (Coleoptera, Curculionidae, Scolytinae) with a pyrethroid insecticide: Effect on the insect community of the olive grove. Chemosphere 80: 35-40.