Eight-toothed spruce bark beetle (Ips acuminatus)
Kolk A. and Starzyk J. R. 1996.The Atlas of Forest Insect Pests. The Polish Forest Research Institute. Multico Warszawa. 705 pp.
Europe, the northern Asia to Japan, also in Asia Minor.
The Scots pine and other pine species.
Adults are 2.2 - 3.7 mm long, cylindrical, robust, reddish-brown to dark brown or brownish-black color. Elytral declivity is with 3 teeth on each margin side. First tooth is the smallest one and the third is the biggest.
Adults overwinter in galleries. They initiate flying in late-May or early-June. I. acuminatus is polygamous species. The nuptial chamber is prepared by the male, which attracts up to 12 females. After mating, females construct egg galleries going rather along fibers and quite deep in the sapwood. Egg galleries are up to 20 cm long and 2.5 mm wide. Shredded wood is not coming out of the gallery like in case of other bark beetles, thus a detection of attacked trees is difficult. Usually the crowns of infested trees fade quite late (in late-June), when the insect is already in the pupal stage. Female lay eggs in cut niches irregularly. Larvae feed under the bark and pupate at their ends, in chambers slightly deeped into the sapwood. After hatching in July, young adults have maturation feeding first around the places of pupation. After emergence from the stems, they continue maturation feeding in current pine shoots or the root collar of 2-5 year old pines. Depending on the weather conditions, the second generation and also sister one is possible.
I. acuminatus infests the upper part or big branches of standing trees. It can cause the death of trees. It is one of the most serious secondary pests of pines, because it attacks relatively healthy trees and infested trees are difficult to recognize. However it usually occurs locally.
Preventive measures and control
Removal of all infested trees during the whole year. Windthrows and newly-cut trees should be removed before the adult emergence. The use of trap trees with tops is recommended in old stands with abundant populations of the pest. The terms of exposure and numbers of trap trees are similar to those for Phaenops cyanea. The most suitable trees for traps are healthy trees with a large portion of the thin bark. If infested cut tops and thick branches can not be utilized or removed from the forest in a distance further than 3 km before the emergence of adults, they should be sprayed with insecticides or burnt.