The dynamics of distribution of quarantine wreckers of the wood on forest areas is given in the study. For the analysis of economic value of insects pests in plantings of regions with various woodi-ness, the density of distribution of wreckers and diseases of the wood in forestries was calculated. In the territory of Irkutsk region in five forestries: Zalarinsky, Ziminsky, Kachugsky, Usolsky, Chere-mkhovsky, the centers of wreckers of the wood of the Siberian drinker moth work, and the total area of damage caused by wreckers makes 16 104.4 hectares. In comparison with 2013 the area of the centers of quarantine wood wreckers decreased by 70 496.0 hectares. Following the results of availa-ble data the high rate of density of the centers was recorded in 2013, and low was in 2006. The maxi-mum density of mass reproduction of wreckers was noted in the Cheremkhovo forestry in 2014, and minimum was in Mamsk. On the border of two for-est areas of Irkutsk region the reasons of dwarf -pines drying at the expense of bacterial dropsy were revealed. The illness in Cis-Baikal was regis- tered for the first time; it was inherent for the south-ern regions. As a result of conducted work in 2012 on forest pathology monitoring by ground method the drying of cedar plantations in the area of 3645 hectares was found. Illegal production of a pine nut was the established reason of epiphytoty. In 2014 the focus of bacterial dropsy in cedar stands in Slyudyanka forestry in the area of 1496.8 hec tares was discovered. Analyzing the available indicators, the high level of density of the centers the lowest was recorded in 2013, and in 2006, at the same time the maximum density of mass reproduction of wreckers was noted in the territory of Cheremkhovo forestry in 2014.