Presence of Quercus Suber Soft-Leaf Defoliators on Trees with Distinct Foliar Monoterpene Emission Profiles

Abstract

Featured Application: This work could serve as a basis for exploring the potential value of applying remote sensing and geographic information system procedures to elaborate defoliator risk maps based on differences in soft-leaf defoliator activity associated with the relative position of Quercus suber trees within stands, as well as differences that can be found in the appearance (size/colour) of leaves from cork oak trees exhibiting distinct foliar monoterpene emission profiles. The cork tree, Quercus suber L., is a characteristic species of the Dehesa agrosilvopastoral system, typical of western Spain. Defoliating insects are an important component of these ecosystems. This study assessed the presence and impact of defoliators feeding on Q. suber soft leaf tissue and their relationship with foliar monoterpene emission profiles. Samplings consisted of weekly tree beating (15 times per tree per sample) during the flight period of key species. We studied 26 cork trees with known profiles of foliar monoterpene emission (13 pinene and 13 limonene chemotypes). We identified a total of 272 larvae from 9 species. The main species were Catocala nymphagoga Esper (40.8%) and Periclista andrei Know (27.6%). Notably, 70.6% of larvae were found on trees with a pinene chemotype. The combined abundance of the four key defoliator species (C. nymphagoga L., P. andrei, Bena bicolorana L., and Cyclophora punctaria L.) was 62.7% lower on limonene-chemotype trees than pinene-chemotype trees. Significant differences were found in defoliation damage between leaves with distinct terpene emission profiles. These results suggest that both the abundance and damage caused by defoliators differ with trees’ emission profiles, and this may indicate differences in palatability and/or nutritional quality between Q. suber trees with distinct foliar monoterpene emission profiles.