Host Vascular Plants for Pests in the Hydrographical Basin of the Otăsău River , Romania

This study was carried out to investigate vascular host plant distribution in the hydrographical basin of the Otăsău River (Vâlcea County, in the Central Southern part of Romania). In order to determine the existing species in this area, fresh and dry material were collected. Specie identification was made based on a repetitive observation of the plants. A taxonomical aid was used to identify the species and classify them into different categories. In this research 368 taxa were investigated and registered as host vascular plants for pests from the studied area. The geoelement analysis shows that Eurasian, European, Central European, Cosmopolite and Circumpolar elements are predominant. Concerning the bioform spectrum the most representative components of the herbaceous layer are hemicryptophytes with 127 taxa. The study reveals that the studied area presents a high floristic diversity of the vascular plants (about 10% of the Romanian flora).


Introduction
The analysed territory is located in the middle part of Vâlcea County, in the Sub-Carpathian region of Oltenia, Romania; its northern limit is represented by the southern part of Buila Vânturariţa National Park, while, in the south, is limited by Băbeni town, where the Otăsău River flows into the Bistriţa River (Fig. 1).
The influence of the milder climate characteristic to Oltenia is quite obvious within the analysed territory, especially in the case of the southern slopes.
The hydrographical network is represented by the Otăsău River, which stems from Muntele Piatra/Stone Mountain (1581 m); it gathers the streams from the southern slopes of Piatra and Albu Mountains (Bulzului Valley, Pătrunsa Valley) and flows from north-west to south-west and, then, it flows into the Bistriţa River, within Frânceşti settlement.Its most important tributaries are the Bulzu and the Tisa streams; the confluence area being located in the proximity of Bărbăteşti settlement (Ujvari, 1972).
The high diversity of the relief is due to the altitude, orientation of the Sub-Carpathian summits which is generally from west to east showing an alternation of valleys and depressions, the presence of the Otăsău floodplain, the geomorphological particularities of all the relief forms, etc. (Fig. 2).
In the work entitled 'Short presentation of the flora of Romania', Grecescu (1898) mentioned some taxa from the region.Most of the mentioned taxa, with few exceptions, were also identified by us.
Scattered data on the flora and vegetation from the Otăsău basin also appear in certain papers elaborated by Buia and Păun (1960); Popescu (1974); Popescu et al. (2001Popescu et al. ( , 2003) ) However, all these studies make reference only to the mountain region.
In the neighbouring hydrographical basins, there have been made numerous studies of the flora and vegetation (Răduţoiu, 2008).
There have not been found any studies regarding the flora from the horticultural crops of this territory.
In Oltenia, studies regarding insect fauna have been carried out by Bobîrnac et al.

Materials and Methods
The first step in the research was to consult the scientific literature.Based on the documentation from this field, we conducted a personal repetitive research in order to observe the current situation of the flora and the interaction between the place and the pest agents.
The taxa were collected in bags in order to be immediately identified in the laboratory.
The author's abbreviations were made according to Brummitt and Powell (1992).
The families were mentioned in systematic order.For each family, genera and species were inserted in alphabetical order.
The determination of the entomological material was realised using the binocular loupe and different field guides from Panin (1957); Rogojanu and Perju (1979); Perju et al. (1983); Stănoiu and Năstase (1998), in the Entomology Laboratory of the Faculty of Agriculture and Horticulture from Craiova.

Results and Discussions
The research was carried out in the lower basin of the Otăsău River, that revealed the presence of numerous vascular plants (368 taxa) that are possible host species for the pests occured in the area.Their presentation is made on families, in systematic order, as follows: EQUISETACEAE:  With regard to the analysis of bioforms, the first position is occupied by hemicryptophytes with 127 taxa (35%).They represent the main components of the herbaceous layer (Fig. 4).
In Table 1 entomofauna is rendered which was collected from the Otăsau basin.Its grouping was made according to the place where the host plant was found.

Conclusions
The pest identification form this territory indicates the floristic diversity of this basin.There was registered a higher frequency in the case of the plants cultivated by local people in this region.Among the identified species that are hosts for animal pests we render the most popular ones found in the basin of Otăsău River: Hyphantria cunea L.
Fig. 1.Delimitation of the investigated area