Ribbed pine borer (Rhagium inquisitor)
From Bugwoodwiki
Kolk A. and Starzyk J. R. 1996.The Atlas of Forest Insect Pests. The Polish Forest Research Institute. Multico Warszawa. 705 pp.
Contents |
Occurrence
Europe, Siberia, the Caucasian mountains, the northern Asia.
Host plants
This is a polyphagous species preferring the Scots pine and other pine species. It was also observed on other conifers and even deciduous species, like the birch, oak and poplar.
Morphology
Adults are 12-15 mm long. The body is black or brownish, shiny. Elytrae are yellowish, covered with grayish pubescence, with 2 black bands across and several yellow or black spots. Pronotum is with a spine on each side. Antennae are twice shorter than the body. Eggs are white, elongated, of 1.8 x 0.5 mm in size. The larva is yellowish-white, up to 30 mm long. The body and head are much dorsal-ventrally flattened. There is no spine on the 9th segment of the abdomen. The pupa is white, 20 mm long with the slightly elongated head.
Biology
Adults are active from April through August. They are often observed on flowers of different plant species or on the breeding material. Females deposit eggs into bark crevices or in empty old galleries under the bark. Larvae hatch 14-25 after oviposition and feed under the bark. Their galleries are up to 1-2 cm wide and filled with frass and brown shredded wood and bark. Pupation occurs in September through October. Wide, oval pupal chambers of 20-40 mm in length are placed between the bark and the wood, and surrounded with a ring of wood chips. This species has one generation per 1 up to 3 years, depending on the weather conditions, thus overwintering may occur in the imaginal, larval or pupal stage. Young adults emerge in spring through round holes of 4-8 mm in diameter and begin supplementary feeding.
Damage
R. inquisitor attacks and kill heavily weakened trees or dying trees infected by fungi, defoliated by foliophagous spcies or growing in polluted areas. It infests mainly the lower parts of stems with the thick bark. At high population density, there is a competition between larvae of R. inquisitor and larvae of other secondary pests like Tomicus piniperda or Ips sexdentatus, leading to decrease of T. piniperda and other species density. R. inquisitor plays a positive role in wood decomposition when infests stumps of conifer trees. It also limit the breeding material for Hylobius abietis. However it can spread fungus spores from infected to healthy trees, thus indirectly causing the blue-staining of the wood.
Preventive measures
Removal of the potential breeding material from woodlands.
Control
Removal of infested trees during a year. In the stands with a high abundance of pine shoot beetles R. inquisitor is beneficial being a natural competitor and a host of numerous parasitoids.
Photo Gallery
 Photo by Robert Dzwonkowski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
