Effect of the pine processionary caterpillar on the growth of black pine: Short- and long-term implications

Abstract

The purpose of this study is to quantify the effect of defoliation produced by the pine processionary caterpillar (Thaumetopoea pityocampa) on the radial growth of the black pine (Pinus nigra). The research considers the hypothesis that the pine processionary caterpillar has a negative effect on the growth of the black pine, given the defoliation suffered by the tree, and that this caterpillar has a tendency to parasitize trees with less growth than those which are not affected. The study begins with an experimental section focused on data collection in the forest of Can Feliu, in Navès (Lleida Province). The fieldwork was primarily based on the extraction of timber cores in the autumn of 2021 from five trees that were attacked by pine processionary caterpillars in 2019 and from five other trees that had not been attacked. By measuring the width of growth rings, the basal area increment per year (BAI) was calculated. Subsequently, by means of graphs, a comparison was made between the trees affected by the pest and the non-affected individuals. The relationship between the climate and the growth of the tree species was also studied. From the analysis of the results, it may be concluded that there exists a decreasing tendency in the annual basal area increment values of the affected individuals, causing the majority of the affected trees not to grow after the attack occurred. Despite the limitations of this study in terms of the sample size analyzed, the results suggest that measures should be taken to control the processionary caterpillar, especially in the current context of climate change.