Research Journal of Agricultural Science, 46 (2), 2014 FAUNA OF HETEROPTERA IN ALFALFA FIELDS IN THE REGION OF BAČKA (NORTHWEST SERBIA): PAST AND PRESENT SITUATION Aleksandra KONJEVIĆ, Tatjana KEREŠI Faculty of Agriculture Novi Sad, University of Novi Sad, Serbia Faculty of Agriculture Novi Sad, Trg Dositeja Obradovica 8, Novi Sad, [email protected] Abstract. Research of insect fauna in alfalfa fields in the region of Vojvodina has been neglected for more than twenty years. During the second half of the last century, many authors from former Yugoslavia investigated this topic: JOVANIĆ (1957), PETRIK (1959), BALARIN (1974), PROTIĆ (1987), KEREŠI & SEKULIĆ (1994). Despite rich diversity of insect fauna in alfalfa updated data on this topic are lacking, especially on Heteroptera in this crop. This can be explained by the fact that alfalfa makes only 4% of all crops raised in this region and that mainly pest species of economic importance are emphasized during the years of their mass appearance, exclusively. For this reason the aim of this study was to compare situation on heteropteran fauna diversity in alfalfa fields in the region of Bačka, with reference on investigations during the period 1981-1985 and in 2012. Special attention was paid to changes in bugs’ diversity, domination of species and economical threats by certain species. Sampling of Heteroptera was conducted in period from late spring to midsummer, during the period of high activity of bugs with respect of plant-host phenology. Adults were collected with insect net and by hand. Collected specimens were identified in the laboratory at the Faculty of Agriculture Novi Sad according to morphological characters and by using different keys for identification: BEI-BIENKO et al., 1964; PÉRICART, 1987; WYNIGER & KMENT, 2010; PROTIĆ 2011; www.macroID.ru; www.koleopterologie.de, etc. During the five years period of sampling 18 species belonging to six families of Heteroptera were registered, while in 2012 there were 26 identified species belonging to nine families. Dominant species in both periods of sampling were phytophagous species with polyphagous preferences, not strictly related to alfalfa. On the other hand the presence and abundance of predaceous species is also recorded what can be of importance in planning biological control program. Results of this study are an overview of the true bugs fauna present in the region of Bačka and represent the contribution to faunistic knowledge of Heteroptera in Serbia. Key words: Heteroptera, fauna of true bugs, alfalfa INTRODUCTION Alfalfa is one of the most important forage crops worldwide and together with red clover is one of the two most important perennial legumes in Serbia (KATIĆ et al., 2005). It is a versatile crop which can be used as pasture, hay and silage. It has the highest yield potential and one of the highest feeding values of all adapted perennial forage legumes. The great importance of alfalfa is reflected in fact that this plant is the biggest source of protein per unit area, 2000-2400 kg/ha. Its relatively high levels of calcium, phosphorus and magnesium are important in balancing mineral requirements of livestock. Grown over a wide range of sod and climatic conditions, alfalfa plays an important role in crop rotation. Staying on the same field three to five years alfalfa and other legumes provide highly suitable habitats for the reproduction of a large number of pests, pathogens and weeds, which not only reduce yields, hay and seed quality but also shorten the life spans of forage plants. In the region of Vojvodina Province alfalfa makes only 4% of all crops raised in this 115 Research Journal of Agricultural Science, 46 (2), 2014 region therefore investigation of insect fauna, especially heteropteran species, were neglected. Data presented in this work are supplement to current knowledge of Heteroptera in Serbia. MATERIAL AND METHODS Heteroptera, or true bugs, examined in this study were sampled from late spring to midsummer, through the period of high activity of true bugs with respect of plant-host phenology. During days with warm, calm weather without wind insects were sampled with sweep net and by hand. In such conditions most of the specimens, especially phytophagous one with potential threat of being pests, spend time on vegetation. Therefore this method of collecting is considered suitable. In the first period of sampling from 1981-1985 insects were collected at one locality 15 km western from Novi Sad, in period from April to August. Sampling was conducted periodically in 15 to 20 days intervals with sweeping net, using 5 times 50 sweeps per field, in diagonal direction. Examined alfalfa fields were in size of about 20-30 hectares and highly irrigated during the growing season. In 2012, the second period of true bugs sampling, trial was conducted in 28 localities all over the North West part of the Vojvodina Province, called the Bačka region. Insects were collected with more attention to edges of smaller alfalfa fields. Examined fields were not in irrigation system, plants were grown in regular climatic conditions in the open fields. Collected bug specimens were examined in the laboratory for entomology at the Faculty of Agriculture Novi Sad. Heteropteran specimens were taken from the sampling pools and only adults were identified according to their morphological characteristics, basically to structure of front wings, legs, mouth parts and antennae. Many keys for identification were used: BEI-BIENKO et al., 1964; PÉRICART, 1987; EVANS & EDMONDSON, 2005; WYNIGER & KMENT, 2010; PROTIĆ 2011; www.macroID.ru; www.koleopterologie.de, www.britishbugs.org.uk; etc. RESULTS AND DISCUSSION All collected Heteroptera, registered in the region of Bačka, during both periods of sampling, belong to nine families and 33 species. Not all of these species are closely related to alfalfa. Many species reach lucerne fields accidentally or are connected more with the weeds, inside or around the field, than with actual cultivated plants, but their presence is of great importance as contribution to faunistic knowledge of Heteroptera in Serbia. During five years period of sampling heteropteran species in alfalfa fields, from 1981 to 1985, there were 18 species recorded belonging to six families: Miridae, Rhopalidae, Coreidae, Pentatomidae, Nabidae and Anthocoridae (Graph 1). According to abundance of collected specimens, the dominant were phytophagous specimens belonging to family Miridae, comprising 53% of sampled pool, followed by predaceous family Nabidae which comprised 44% of sampling pool. Other four families were recorded in less than 5%: Anthocoridae almost 2%, Pentatomidae almost 1%, Rhopalidae 0.1% and Coreidae only 0.02% with only one specimen captured. 116 Research Journal of Agricultural Science, 46 (2), 2014 Fig. 1. Composition of Heteroptera families during period 1981-1985 and 2012 in the region of Bačka, Vojvodina Province, Serbia The dominant family Miridae, plant bugs, represents the largest family in the Heteroptera. About 25% of the true bugs are in this family with 1300 genera and 10.040 species (HENRY, 2009). These are small, terrestrial insects, usually with oval-shape or elongate body measuring less than 12 mm in length. Species composition within the dominant family Miridae, in the study during early eighties, showed huge dominance of Lygus rugulipennis Poppius, with 1161 collected specimens (Table 1), comprising more than 28% of all collected heteropteran species. This species often attains strikingly high density and with wide ecological valence it is considered as pest all over the Palearctic region. In the nearby countries, it has been reported in high densities in Hungary (Erdélyi & BENEDEK, 1974), Ukraine (PUCHKOV, 1966 in ERDÉLYI & BENEDEK, 1974), Poland (BILEWICZ- PAWIŃSKA, 1965) and former Czechoslovakia (OBRTEL, 1969). Also numerous species from the same family was Adelphocoris lineolatus (Goeze), the alfalfa plant bug, representing 4% of sampling pool. This is the common species all over the area of fodder legumes growing. In Serbia, this species was dominant in alfalfa fields, during 1987, in the vicinity of Belgrade (PROTIĆ, 1987), and it has been reported as numerous in Hungary as well (ERDÉLYI & BENEDEK, 1974). These two species were followed by A. seticornis (Fabricius) and Trigonotylus ruficornis (Geoffroy), which were represented in sampling pool by 1.33 and 1.14%, respectively. Species Lygus pratensis (Linnaeus) and Stenodema calcaratum (Fallen) were captured in less than 1%, although they are common part of insect fauna in different crops (PROTIĆ, 1987; KEREŠI, 1993). Nymphs of this family were not identified to species, due to their changeable characters, but their huge number in sampling pool, almost 18%, indicate the dominance of this family in alfalfa fields. 117 Research Journal of Agricultural Science, 46 (2), 2014 Table 1 List of Heteroptera species captured during two periods of sampling in the region of Bačka, Vojvodina Province, Serbia 1981-1985 2012 Family Species number % number % Miridae Lygus rugulipennis 1161 28.13 - - Lygus pratensis 3 0.07 5 3.47 Lygus wagneri - - 1 0.69 Stenodema calcaratum 1 0.02 2 1.39 Adelphocoris lineolatus 169 4.09 - - Adelphocoris seticornis 55 1.33 - - Trigonotylus ruficornis 47 1.14 - - Polymerus vulneratus - - 2 1.39 Chlamydatus pullus - - 1 0.69 Chlamydatus pulicarius - - 3 2.08 nymphs 747 18.10 4 2.78 Lygaeidae Peritrechus gracilicornis - - 1 0.69 Metopoplax ditomoides - - 1 0.69 Nysius senecionis - - 5 3.47 Pyrrhocoridae Pyrrhocoris