Enhancing the Biodiversity of Insects Pollinators through Flowering Grass Strips

The extensive use of plant protection products in agricultural practice and obtaining high and top quality yields results in decline of a major part of the natural regulators and the insects-pollinators. The reduction in their numbers in agricultural areas poses a threat for the pollination of entomophilous plants on global scale. The objective of this study was to establish areas of flowering varieties of grass mixes, ensuring proper habitats and food source for the pollinators of agricultural crops. The tests showed that the plant varieties in the grass mixes blossomed in the period April to June (1.5-2 months), providing varying species of pollinators, depending on the plants species. In the different-coloured layers of the grass mixtures: white, purple and yellow, the following pollinators were determined: Apis mellifera L., Megachile sp., Halictus scabiosae Rossi, Lasioglossum xanthopus Kirby, Melita leporita, Andrena flavipes Panzer., Macropis europaeae Warn., Anthidium manicatum L., Ceratina cucurbitina Rossi and Ceratina sp.


Introduction
Bees are considered as major pollinators of crops worldwide.Approximately 35% of the food for human consumption is directly or indirectly dependent on pollination by insects, which improves the yields of agricultural plants (Watanabe, 1994;Delaplane & Mayer, 2000).The preservation of the pollinators is a serious challenge in the last decades.Most significant factors impacted bees behavior proved to be human activities, loss of essential habitats due to the decrease of natural areas with flowering plant varieties, extensive use of insecticides for pests control, as well as climate change (Goulson, 2013;Vanbergen, 2013;Kerr et al., 2015;IPBES, 2016).It is demonstrated (Maurizio, 1950;Mattila & Otis, 2006;Naug, 2009) decline of pollen quantity leads to change in biochemical composition of the nectar of the intensively cultivated crops and results in loss of bee families.Bees decline causes significant losses in agriculture, since more than 90 % of the crops need pollinators or pollen carriers for cross-pollination (Proctor et al., 1996;Nabhan & Buchmann, 1997;Roubik, 1995;Klein et al., 2007;Ollerton et al., 2011;Kevan & Phillips, 2001;Aizen & Harder, 2009).In this respect, the value of bee honey, produced in the EU, amounts to approximately 140 million euro (Moritz et al., 2010), while the value of pollination for the European agriculture is estimated at 20 billion euro (Gallai et al., 2008).
One of the main priority in current Common Agricultural Policy of the European Union regarding efficient use of natural resources is the establishment of various habitats of flowering grass strips.They prove to be a permanent food source for the insects pollinators, providing the necessary nectar and pollen from spring until autumn.It is reported (Carvell et al., 2007;Decourtye et al., 2010), that the flowering varieties, suitable for incorporation in the grass mixes, are Phacelia (Phacelia spp.), clover (Trifolium spp.) and the varieties in the Brassicaceae family.With respect to the colour range, bees differentiate among over 300 colours, with preference to yellow and blue coloured plants, but find easiest the purple coloured plants.The objective of this study is to investigate development and self-maintenance of two kind flowering plant strip, which will ensure the attraction of pollinators prior to the blossoming of the respective crops.jas.ccsenet.

Method
The Megachile in the grass mixes in the second field was the result of the white colour, provided by the white clover and coriander.The purple flowers of Phacelia (Phacelia sp.) attract mainly honey bee (Apis mellifera L.).Therefore it was the second largest species with a total of 79 insects.The other pollinators were not observed significantly.
In the case of the spring sowing (Variant ІІІ and Variant ІV) blossoming started in the second decade of May and lasted until the end of June for a total of 40 days.The largest number of pollinators was determined in the first decade of June.
In Variant ІІІ of the varieties, included in the grass mix: White mustard, Phacelia (Phacelia sp.) and various types of clovers (crimson, Egyptian and white), the white mustard (19-20.05)was again the earliest to blossom, but 47 days later, compared to the autumn sowing (Variant I).The blossoming of Phacelia (Phacelia sp.) started on 27 May and lasted until 26 June.These two varieties formed the two-level the grass mix: bottom yellow level and top predominantly purple level.All clovers (crimson, Egyptian and white) blossomed in second half of June, as the predominant colours in the mix were red and white.During the mass blossoming, the field was coloured in these colours.The following insect species were identified: Apis mellifera L., Megachile sp. and Macropis europaeae Warn.The predominant species was Megachile sp., with a total of 13 representatives.
In Variant ІV the predominant plant variety was coriander blossoming from the second decade until the end of June (18.06to 30.06).Its white flowers attract predominantly species from the genus Megachile sp. and a total of 55 insects were reported.In order seed mixtures to be applicable for farmers for long-term use, it was important to investigate the duration of their self-maintenance (self-sowing and repeated flowering).Self-sowing observed in Variant ІI and Variant ІV, only.These plots formed grass cover after over-wintering, in 2015.Dominated species were white clover and Phacelia (Phacelia sp.) and flowering observed from the beginning of May and until July.They formed two coloured layers in the grass plots-white and purple.
The following species were observed in Variant ІI: Apis mellifera L., Megachile sp. and Ceratina cucurbitina Rossi.Apis mellifera L. was attracted by the purple flowers of Phacelia (Phacelia sp.) and Megachile sp.-by the white colour of the clover.
Only species of the genus Megachile sp were observed in Variant ІV.In both variants, predominant insect was genus Megachile sp.(Variant II-71 insects, Variant IV-75 insects), due to their attraction of the dominant white colour in the grass mixture (Table 1).
The mixtures of autumn sowing are more suitable to put near autumn crops, in order to ensure flowers early spring.For the spring field crops, the mixtures with spring sowing are more appropriate to ensure proper presence of pollinators.The varieties Phacelia (Phacelia sp.), White mustard, coriander and white clover enable the possibility for self-sowing in the summer-autumn period.
The purple colour in the grass mix is provided by Phacelia and mostly attracts honeybees.The white colour of white mustard, coriander, Egyptian and white clover attracts predominantly species of the genus Megachile.
The establishment of a plantation of Phacelia, along the agricultural areas, may be used for reproduction and preservation of the pollinators during plant-protection activities in agricultural crops.

Table 1 .
Pollinator species in the grass mixtures in 2014-2015