|Summary: Leafminers are defined as insects which larvae are endophagous i.e. they feed inside the leaf, between two laminae, hollowing out a mine (hyponomium) that is visible as an area of discoloration.|
The aim of this research was to identify the leafminer species on oaks (Quercus robur, Q. petraea, Q. pubescens, Q. ilex) in Croatia. The research lasted three years. Leafminers were collected on several locations in continental and submediterranean part of Croatia. Leafminers were collected with mines in different larval developmental stages, reared to pupae and adults when needed for identification. The species were identified by the main diagnostic characteristics: adults, pupae, shape and colour of leafmines, its position on leaves, frass-lines and host plant. In total, 15 leafminer species from 3 insect orders (Lepidoptera, Hymenoptera and Coleoptera) on 4 oak species were found, order Lepidoptera being the richest by the number of species found. The following species were found: Acrocercops brongniardella, Phyllonorycter roboris, P. heegeriella, P. harisella, P. quercifoliella, P. lautella, P. parisiella, Tischeria ekebladella, T. dodonea, T. decidua, Coleophora kuehnella, Stigmella roborella, S. samiatella, Profenusa pygmaea, Orchestes quercus.
Out of 15 species found, 8 can be considered as new records in lefminer fauna on oaks in Croatia. Those are: Phyllonorycter roboris, P. heegeriella, P. harisella, P. lautela, P. quercifoliella, Tischeria dodonea, T. decidua and Profenusa pygmaea. Leafminers are specific in their choice of food, i.e. in the choosing tissue, organs and plant species on which they feed. Leafminers found during this research have varied in their choice of host plant, 1 species found is first degree monophag, 3 species are second degree monophags, 6 species are third degree monophags and 5 species are first degree olihophags. Relatively small number of leafminer species can be described as serious pests on woody plants. Tischeria ekebladella can be considered as forest pests in nurseries and on young oaks. Acrocercops brongniardella and Phyllonorycter lautella were found on oak seedlings and in higher population densities could influence the photosinthetic ability of oak leaves. Other species found during this research were regularly present on oak seedling and trees but none of these species caused neither ecological or economic damage.