Xylophagous entomofauna in branches of oaks (Quercus spp.) and its significance for oak health in the Karst region of Slovenia

Abstract

Samples of dying branches from 121 trees of Quercus pubescens, Q. cerris, and Q. petraea were taken from 102 sites in Seslerio autumnalis-Quercetum petraeae and Ostryo-Quercetum pubescentis forests. After nine months' rearing in eclectors, branches were cut to 20-cm sections, and signs of infestation as well as larvae and adult insects were noted. We analysed 395 sections of branches from Q. pubescens, 125 sections from Q. cerris, and 85 sections from Q. petraea. We found 44 adult insects: 45% were from the Cerambycidae family (Callimus angulatus ssp. angulatus, Poecilium alni, and Exocentrus adspersus), 18% were from the Scolytinae subfamily (Scolytus intricatus, Xyleborus dispar), 4% from the Buprestidae family (Coraebus florentinus), 4.5% from the Cleridae family (Tilloidea unifasciata), and 28.5% from other families. In addition, 145 larvae were found: 50% from the Cerambycidae family, 39% from the Buprestidae family, 4% from the Scolytinae subfamily, and 7% from other families. Significant difference in the abundance of adult insects and larvae with regard to the diameter of branch sections and the host species were found. 78% of dying branches showed signs of infestation. Species of the Buprestidae, Scolytinae, and Cerambycidae represent important factors in the decline in oak vitality in the lower Karst region of Slovenia.

The effects of oviposition site on the development of the wood borer Coraebus florentinus (Coleoptera: Buprestidae)

“…This reduction in the number of branches results in a progressive decay and loss of vigour (Jurc et al, 2009). The symptoms of the damage are easily identifiable and are widely described in the literature (Bachiller et al, 1981;Montoya, 1988;Soria & Ocete, 1993;Cárdenas & Gallardo, 2012).…”

“…Temperatures were recorded daily, once every hour while the sun was shining (7 am to 10 pm), during the two first weeks of July, when C. florentinus is ovipositing (Jurc et al, 2009). The average values were statistically compared in order to determine whether the temperatures in the north and south facing, and upper-and lower-halves of the canopy differed significantly (data are given in appendix 1).…”

“…The abundance of this insect is greatest in several countries in the Mediterranean basin (Italy, Spain and Portugal; Jurc et al, 2009), where the level of damage has considerably increased recently. This is because of the progressive abandonment of pruning before the emergence of the imago (Lombardero & Fernández de Ana Magán, 1996), although this is considered the most effective method of control (Evans et al, 2004).…”

“…Adults of C. florentinus emerge for a very short period of time (June and July; Jurc et al, 2009) and although they feed on the leaves of their host plants, the defoliation they cause is not significant. This jewel beetle is most active during the hottest hours of the day and, preferably, on distal branches, which are most exposed to the sun.…”

Long-Term Assessment of Selective Pruning of Quercus Species for Controlling Populations of Coraebus florentinus (Coleoptera: Buprestidae) in Mediterranean Forests

“…At the end of the larval stage, the insect changes its boring direction, turning in the gallery and interrupting the sap flow. This causes the death of the branch upon completion of metamorphosis [3,4].…”