Vulpia myuros (L.) C.C.Gmel (Rat's-tail Fescue) – A Problem Weed in the Rape Crops of Our Country

The fact that in a number of locations in Giurgiu, Dâmboviţa and Arges County rape crop was severely affected by the presence of the Vulpia myuros species this spring, has led us to take the survey and analyse the premises that favoured the species installation and development. Soil samples and Vulpia plants were taken to establish their characteristics. Soil features correspond to the ecological requirements of the species. The morphometric values recorded on field plant are exceeding the data recorded in the literature. Any herbicide used had no effect on Vulpia plants growth. The establishment by direct seeding of rapeseed crops and bare spots in the field were the precondition for the installation and propagation of Vulpia myuros plants that caused severe harvest decrease.


Introduction
Vulpia myuros known in our country as a species of dry, rocky places, oligotrophic, xero-mesophyulous, subtermophyllous, moderately-strongly acidophilic [15], was reported as grass weed problem in winter crops in Australia, USA, the Netherlands and Denmark [11].
V.myuros is an annual or winter annual species [7] that multiply only by seed. These survive in the soil a limited period [10]. Seeds germination occurs in autumn, under cool soil temperatures and adequate moisture and, for inflorescence formation and flowering in the following spring, the plant requires a period of vernalization [2].
According to Mathiassen et al. [11], V.myuros plants aren't competitive in a dense crop, but they may be set in bare spots of the fields from where they can infest the area and cause severely crop losses. Control of V.myuros became difficult when crops are established by direct seed systems and so the soil disturbance is low; due to the morphological characteristics (shallow rooted) plants are not affected by the minimum tillage system [2,10].
Ball et al. [2] observations show that reliance on glyphosate for weed control in fallow favored the expansion of this species. The experiences of Min et al. [13] indicate that V.myuros has a high tolerance to a variety of herbicides, due, after Hull et al. [10], its natural tolerance to ACCase inhibiting herbicides. Also, the decomposed residues of V. myuros affect adversely the wheat growth because their allopathic substances [3]. Aqueous extracts of rat's tail fescue inhibited seed germination, coleoptile and root growth of wheat [12].
So far, in the literature of our country, Vulpia myuros was mentioned in connection with studies of phytosociology in diverse areas: Bucharest, Codru Moma Montains, meadows of Subcarpathian Ialomița etc. [1,4,5,14]. The main works on segetal flora in our country does not mention the existence of this species as a crops weed [6,8]. It is for the first time that this species is recorded as weed in rapeseed in our country (Romania). This article describes the behavior of this species in the particular conditions of three areas in Romania where it was identified.

Materials and Methods
Observations were conducted in winter rape crops in rural Mihăileşti (Giurgiu County), Mircea Voda (Dâmboviţa County) and Mioși (Arges County) where V.myuros infestation caused significant crop losses.
In the fall of 2013, at the setting up the rapeseed crop in Mihăliesti town, soil samples were taken to determine its characteristics (pH, humus, nitrogen, phosphorous and potassium content, C/N, nitrogen index etc.) and to establish a proper fertilization plan. These data were compared with the ecological requirements of the Vulpia myuros species.
At the time of flowering -June 2014, and at the end of growing season -July 2014, specimens of the V. myuros plants were taken from rapeseed crop from Mihăliesti town to establish their morphological characters (plant size, inflorescence length, number of flowers / spikelet etc.).

Results and Discussion
Rapeseed culture was established by direct seeding in all 3 areas.
On the lands of Dâmboviţa and Argeș County rapeseed culture has followed after cereal crops. Pictures taken in October on these lands show the degree of invasion by Vulpia myuros plants (Figure 1, 2).  The infestation degree was not reduced by herbicides applied, e.g. Prosper or Agil 100 EC, the last in a dose of 2,5 l/ha.
In the Mihăileşti town the rapeseed crop was established on a land which was fallow until 2013. Data resulted from soil analyses (Tab. 1) have led to the following scheme of fertilization: fall -400 kg/ha NPK and 200kg/ha NAC; spring: 200 kg/ha urea. Rape culture establishment was made by using 60 germinable seeds/m 2 . Post emergence herbicide Cleranda was applied.
Soil features correspond to the ecological requirements of the species.
As in the previous cases, Vulpia myuros infestation was observed early as autumn. Spring the herbicide Pulsar 40 application have no effect on Vulpia plants. The appearance of the rapeseed crop in June can be seen in Fig.3 and 4.   moderately acid medium medium good medium medium low nitrogen supply medium high fertility pH -soil reaction; N -total nitrogen content; K -potassium content; P -phosphorus content; V% -the degree of base saturation; IN -nitrogen index; T -cation exchange capacity; C/N -cellulosic substances/protein substances Morphometric data of Vulpia plants harvested from Mihăileşti rapeseed culture were compared with existing data in the literature of our country [9] (Table 2).    An assessment made at the end of the growing season indicated that the density of rapeseed plants was about five/m 2 ( Figure. 6, 7).

Conclusions
Our study reveals a new situation, unprecedented in the literature of our country, about the behavior of V.myuros as weed species in winter rape culture.
Comparing literature data with our field observations the establishment by direct seeding of rapeseed crops was the precondition for the severe harvest decrease.
Bare spots in the field have allowed the installation and then propagation of Vulpia myuros plants though the rapeseed crops are dense.
This observation leads us to expand our research in the future; issues that will be pursued are: area and cultures in our country where the species is present; existence of 154 Vulpia myuros (L.) C.C.Gmel (Rat's-tail Fescue) -A Problem Weed in the Rape Crops of Our Country allopathic effects on rape plants; control options of V.myuros species populations through various methods etc.