Observations on biological control agents of weeds of natural meadows

Abstract

The observations were made in the period 2008 – 2010 in natural pastures from the department of Iassy, nort-east of Romania. In majority pasture ecosystems exploited by grazing, it is happening a transformation of flora composition, frequently through adaptation in this surfaces with desirable species (weeds) with low economic value. The researches were done in the pastures invaded bt Lepidium draba L. – the result of irrational grazing of livestock respectively cows and horses. Lepidium draba L. (family Brasicaceae), originary from Europe, became a problem plant in many agricultural ecosystems from our country. Three of the most promising biological control agents, the gall-forming weevil Ceutorhynchus cardariae, the flea beetle Psylliodes wrasei, and the gall mite Aceria drabae occur at this site. Attack by gall mite Aceria drabae Nal., of inflorescences by Lepidium draba L., is based on visual examination of plants, were contained between 15 -47,5% in 2008 and were contained between 18,8 – 43,4% in 2010. Plant numbers were analysed using repeated measures analysis of variance. The density of L. draba was four to five times higher in Iasi, presumably because of the long history of stronger grazing pressure on the associated vegetation. On variant to have beened disturbed (harrowed) and disturbed and cultivated and mixture of grass seeds, significantly reduced the number of L. draba plants.