Butterfly caterpillars and cicadas damaging Swiss forests
In the Saas Valley and Goms, foresters have been observing yellowed needles and needle loss in larch trees since the beginning of June.
Some trees were completely defoliated.
The cause was caterpillar feeding by a native butterfly, the scarce umber moth (Agriopis aurantiaria). Mass outbreaks of this species have rarely been observed until now. “Apparently, the climatic conditions prevailing in recent times have favoured strong population growth,” writes the Forest Protection Switzerland (WSS) unit of WSL in a publication. In the meantime, the affected trees have responded with a second flush of growth.
At around the same time, damage reports from the western Swiss Jura arc reached WSS. At several sites, black and Scots pines displayed conspicuous needle discolouration. Responsible is the pine spittlebug (Haematoloma dorsata), identifiable by ring-shaped feeding marks on the needles. “This cicada species originates from more southerly regions of Europe and has expanded its range northward over recent decades,” writes Forest Protection Switzerland. Individual records of this species have been registered in Switzerland for several years, though damage to needles of such severity had not previously been recorded here.
Forest Protection Switzerland wishes to document the extent of damage caused by both species across Switzerland. It is therefore requesting reports of suspected cases via the reporting form (http://www.wsl.ch/wss_formular).
