Scolytus scolytus Fabricius, 1775

[Hungarian Version]

Csóka, György and Kovács, Tibor (1999): Xilofág rovarok - Xylophagous insects. Hungarian Forest Research Institute. Erdészeti Turományos Intézet, Agroinform Kiadó, Budapest, 189 pp.

Mn: Nagy szilszíjács-szú  /  En: Large elm beetle

4-6 mm. Usually univoltine, but in favourable years can produce two generations. Foodplants are elm (Ulmus) species. The vertical, single-shafted egg gallery is 2.5-3 mm wide and 3-10 cm long, located in the bark and the inner bark. The larval tunnels (up to 15 cm long and widening and bending towards the end) leave the maternal egg-laying tunnel at right angles. The emerging beetles search for new foodplants, and after finding a host they feed on the forks of younger branches. During this maturation feeding they infect the tree with the spores of the fungus Ceratocystis ulmi (Dutch elm disease) transported from the tree in which they developed. The fungal infection spreads in the sapwood, causing death of branches and later death of the whole tree. The beetle and the fungus live in mutualistic relationship. While the beetle serves as a vector for the fungus, the pathogen weakens the tree providing a suitable food source for the bark beetle larva. Probably the larvae could not properly develop in totally healthy trees. The large elm beetle and several closely-related species (S. multistriatus, S. ensifer, S. laevis) with a similar life history have played significant roles in the spread of Dutch elm disease and in the dramatic decrease of elm trees throughout Europe. Can be found everywhere in Europe, also common in Hungary.


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