Insects and mites in the fauna of Serbia - importance for the classical biological control of weeds

Abstract

Territory of the Republic of Serbia, as the central area of the Balkan Peninsula, is of particular interest as a point where biological entities coming from central Europe, Asia Minor, Mediterranean and North Africa encounter. Hence, this area has been declared as a "center of European biodiversity". Natural consequence of Serbia's geographic position and the richness of the flora is the great diversity of insect fauna (Insecta). Observed diversity of entomofauna is the reason why the territory of Serbia is attractive for the research in biological control. Climate change and the intensive exchange of biota as a direct consequence of increasing global trend of trade between the countries is what make this a particularly important issue. Although Serbia has a relatively short history of research on phytophagous insects as biological control agents for Eurasian origin weeds, researchers at the biological laboratory of Institute for plant protection based in Zemun (presently Institute for plant protection and environment, Zemun) can be considered as doyens of biological control research in Europe and even worldwide. The first department for biological control of pests in Europe started working in the Institute for plant protection in Zemun, in 1954. The founder and the first director of the Institute for plant protection, prof. dr. Guido Nonveiller, had a vision of forming a team of interdisciplinary researchers with biological and agronomic BACKGROUND: . In the period from 1967-1974, the project entitled "Project 480: Europe: Yugoslavia E30-Ent-12 - Distribution and natural enemies of the weeds Dalmatian toadflax (Linaria dalmatica Mill) and Mediterranean sage (Salvia aethiopsis L.) in Yugoslavia", has been carried out for the purpose of biological control of L. dalmatica (Plantaginaceae) and Salvia aethiops (Lamiaceae). Four more projects supported by the USDA followed: Elaboration of protective measures for agricultural crops against parasitic phanerogams belonging to the genera Cuscuta and Orobanche (parasitic herbs - dodders and broomrape) (1968-1971), Biological control of terrestrial and aquatic weeds and pests of crop plants (1977-1983), Biological control of insects and weeds (1981-1986), Biocontrol of Yugoslavian and North American weeds with insects, pathogens and other biotic agents (1988-1990, 1991). Research on potential phytophagous insects against invasive weeds in North America included, beside a forementioned plants, Myriophyllum spicatum L. (Haloragaceae), Carduus nutans, Carduus acanthoides, Cirsium arvense, Centaurea solstitialis, Centaurea maculosa (Asteraceae), Euphorbia cyparissias and Euphorbia virgata (Euphorbaceae). Classical biological control (i.e. intentional release of natural enemies of exotic pests for the purpose of their control) represents a very important tool in the integrated pest management. Globalization and intensive trade between countries have led to exchange of organisms from different zoogeographical regions. Should those organisms adapt to the new environment, they could potentially represent threat to local ecosystems. This is the reason why, according to Agenda 21 (Chapter 14), biological control has been recognized as a method of choice in pest control. Until 1992, the research within USDA Project 480 resulted in introduction of several insect species in the area of North America. Introduced species were: Sphenoptera jugoslavica for the purpose of controlling Centaurea diffusa (Asteraceae), Hylas euphorbiae, Oberea erythrocephala, Pegomya euphorbiae and P. curticornis (Diptera: Anthomyiidae) for the control of invasive spurge species Euphorbia esula, E. cyparissias and E. virgata. Species from the genus Aphthona (Coleoptera, Chrysomelidae), A. lacertosa, A. nigris-cutis and A. flava, were introduced for the same reason. Further, two weevil species, Larinus obtusus and L. minutus (Coleoptera, Curculionidae), were used against Centaurea diffusa and Centaurea maculosa. Lastly, defoliator species Calophasia lunula (Lepidoptera: Noctuidae) was introduced for the control of Linaria dalmatica and L. vulgaris (Plantaginaceae). During the period of 1992-1999, introduced species were Chamaesphecia hungarica and Ch. crassicornis for the control of Euphorbia virgata and Chamaesphecia hungarica for the control of Euphorbia esula. Two moth species, Eteobalea serratella and E. intermediella (Cosmopterigidae), were introduced for the control of north American populations of Linaria vulgaris and L. dalmatica. Finally, after extensive host specificity tests, a weevil species Mogulones cruciger was introduced for the purpose of controlling Cynoglossum officinale (Boraginaceae) in North America. Advances in molecular techniques in the 21st century have led to turn over in biological control research. New knowledge on specific interactions within the insect-plant system has placed in the focus population-genetic properties of the biological control agent. Molecular techniques also enabled understanding biological properties of local insect's populations as well as cryptic speciation, which consequently led to overall better safety and precision in biological control research. The research, since 2000, has been focused on invasive plant species of the genus Linaria and weevils of the genus Mecinus and Rhinusa. New research enabled introduction and successful development of gallicol weevil species Rhinusapilosa in north-west Canada. Furthermore, cryptic species Mecinus janthiniformis was described within the Mecinus jathinus. Within Mecinus heydenii complex of species, one cryptic species were described, Mecinus peterharrisi in association with L. dalmatica and one subspecies Mecinus laeviceps ssp. meridionalis association with L. genistifolia from East Serbia and Bulgaria. One new gallforming weevil species was also described, namely Rhinusa rara in association with L. genistifolia and L. dalmatica from East Serbia, Hungary and South Russia. All newly described species and subspecies are in the research process of suitability assessment as the biological control agents. Besides insects many species of eriophyoid mites, an obligatory plant feeders, are considered to be among the most promising candidate agents for classical biological control of weeds due to their biology and host-plant relationship. Eriophyoid mites have high degree of host specificity, about 80% of currently known species have been recorded on a one host plant. Among approximately 5000 known species about 50 are considered as potential weed control agents in the world. More than 50% of these species have been discovered in Serbia. Investigations in this field started in early 1980's. In the period 1990-2000's in the framework of different projects three new species for science were described on Geranium dissectum L. and four on Euphorbia spp. At the beginning of 2000's, especially detailed studies of Aceria anthocoptes (Nal.) and Leipothrix dipsacivagus Petanovic. et Rector have been carried out from the different points of view. During the last years few eriophyoid mites were investigated within the framework of different European programs of classical biological control of weeds. Aceria acroptiloni Kovalev et Shevchenko was studied as agent of biocontrol of Rhaponticum repens (L.) Hidalgo, Metaculus spp. were studied for biological control of Lepidium latifolium L., Isatis tinctoria and Diplotaxis tenuifolia, as well as two Aceria spp. for biological control of Eleagnus angustifolia L. Moreover two potential biocontrol agents Aceria artemisiifoliae Vidovic & Petanovic, and Aculops mosiniensis Ripka against Ambrosia artemisifolia L. and Ailanthus altissima (Mill) Swingle respectively have been nominated recently. More or less integrative approach in species delimitation has been applied using combined techniques of phase contrast light microscopy, pseudo dark field, differential interference contrast microscopy, confocal laser scanning microscopy, scanning electron microscopy and sequencing of barcoding region of mt COI DNA. Traditional morphological analysis was accomplished with morphometric, (linear and/or geometric) analysis because it helps in understanding intraspecific variability, including races adapted to the host plants and /or cryptic species. Studying potential agents for the biological control of invasive weeds is tightly linked with floristic and entomo-acaro-faunistic diversity. Because of its position, the territory of Serbia represents a meeting point for floristic and faunistic elements coming from central Europe, Asia Minor, Mediterranean and North Africa. The complex floristic and faunistic diversity is also a consequence of numerous colonizations and recolonizations of biota during the periods of glaciation and interglaciation. These unique aspects have made the territory of Serbia an excellent starting point for the research in biological control.