Phytosociological survey of weeds in glyphosate resistant and susceptible soybean cultivation areas

Abstract

The objective of the present study was to perform a phytosociological study of weeds present in areas of glyphosate resistant and susceptible soybeans, in the stage of maximum infestation, in the 2013/14 and 2014/15 crops. The phytosociological survey of the weed community was carried out in Palotina - PR, in glyphosate resistant and susceptible soybeans soybean cultivation areas, in two summer crops, as plants were at physiological stage of maturity (R7). The species are identified and quantified by the square of the inventory (1.0 x 1.0 m), with a sample of 20 m-2 per area, totaling 200 points in each evaluation condition. Calculations were made for density, relative density, frequency, relative frequency, abundance, relative abundance, importance value index and similarity index. In the areas of glyphosate-susceptible soybean cultivation as main species found according to the importance value index (IVI) were: Bidens pilosa, Conyza spp. and Euphorbia heterophylla. As for the glyphosate-resistant soybean cultivation system, the main components are: Conyza spp., Commelina benghalensis and Digitaria insularis. The similarity between the areas of glyphosate resistant and susceptible soybean was less than 80%. It is concluded that there are differences in the weed community, between the areas of glyphosate resistant and susceptible soybeans.