Spatial distribution of four spruce bark beetles in north-western Slovakia

Abstract

Infestation density of four the most common spruce bark beetle species was estimated on 15 study sites (10 trees per site) in the Kysuce model region in 2006. Five half-metre long sections of the stem were selected and dissected at the base of the stem; midway between the base of the stem and the base of the crown; just below the base of the crown; in the middle of the crown; and in the upper part of the crown. The infestation density of bark beetles, expressed as the number of mating chambers per dm<sup>2</sup>, was determined. Ordinary kriging was then used to produce smooth maps and visualize spatial distribution of study species. Maps with isolines indicating high infestation were produced for study species (<I>I. Typographus</I> over 0.38; (<I>I. amitinu</I>s over 0.15; (<I>I. duplicatus</I> over 0.11; and <I>P. chalcographus</I> over 0.415 nuptial chambers per dm<sup>2</sup>). <I>Ips typographus</I> L. remained dominant species on majority of sites having high intensity of infestation. Lower altitudes in the south-eastern part of the region were often infested by <I>I. duplicatus</I> Sahlberg and also by <I>I. typographu</I> and <I>Pityogenes chalcographus</I> L. Higher elevations in the north-eastern part of territory in the vicinity of border with Poland were heavily infested by <I>I. amitinus</I> Eichhoff (often with <I>I. typographus). P. chalcographus</I> was abundant on majority of territory – mainly in southern half of area. However locally, it was found in extremely high abundance. The results suggest the need for control measures set up jointly against the most abundant bark beetle species in study region.