Original scientific paper
OUTBREAK OF THE SPRUCE WEB-SPINNING SAWFLY Cephalcia arvensis (HYMENOPTERA: PAMPHILIIDAE) IN SLOVENIA
Gregor Meterc
; Biotechnical Faculty, University of Ljubljana, Slovenia
Danijel Borković
; Biotechnical Faculty, University of Ljubljana, Slovenia
Maja Jurc
; Biotechnical Faculty, University of Ljubljana, Slovenia
Abstract
The first local outbreak of the field web-spinning sawfly (Cephalcia arvensis) appeared in 2009 on one location on 106 ha in the northern part of Slovenia in a stand of 60-90-year-old Picea abies and on 600-800 m a. s. l. In the period from 2009 to 2011 the density of the prepupae, bio-ecology and defoliation of the trees were studied.
The density of the population of prepupae of Cephalcia species was studied on the six plots in the soil samples (25 x 25 x 20 cm). In 2009 it was high (average = 595 individuals/m2 of soil), while in 2010 the average number of prepupae was lower for 68%. The collected data of soil and air temperatures indicate their impact on the beginning of the emergence of Cephalcia species in 2011; we found that it had started in large number when the average daily temperature was 14.7 °C and the average soil temperature was 8.7 °C.
In the autumn of 2009, six circular plots (50 x 50 m each) were defined where the defoliation of the crowns of 88 conifer trees with the breast height over 10 cm was estimated. The defoliation of P. abies has grown over two years; in 2009, the average defoliation was 28%, and in 2010 it was 32%.
Keywords
Cephalcia arvensis; temperature; defoliation; outbreak; Norway spruce; Slovenia
Hrčak ID:
125674
URI
Publication date:
30.6.2014.
Visits: 1.139 *