در استان تهران )BRASSICA NAPUS. L( شناسايي و تعيين تراكم علف هاي هرز مزارع كلزا

Identification of dominant weeds in canola fields and determination of their densities in Tehran province

To identify and determine density of weeds in canola fields, an investigation was carried out in four localities of Tehran province for two years (2001-2002). Weed densities were determined by quadratic method in W form once per month. Weeds were divided into 3 groups of Graminae, Brassicaceae and other dicot weeds (on the basis of different methods of control) and importance of Brassicaceae weeds. Results showed that the relative density of each groups of above-mentiond weeds was 22.61, 46.24, 31.24 % in South of Tehran, 4.12, 37.87, 42.01 % in Nazar-Abad, 15.34, 35.86, 48.96 % in 1-lashtgerd and 6.22, 20.46, 73.32 % in Varamin, respectively. The mean for the Tehran Province was 12.07, 35.11, 48.88 %. The relative density of Brassicaceae weeds in south of Tehran was higher than other localities. Sinapis arvensis only found in Varamin with 2.4 % relative density. Dicot weeds species were dominant compared to other groups. Dominant weeds included: Descurainia sophia, Cardaria draba, Rapistrum rugosum, Goldbachia laevigata, Erysimum rependum, Capsella bursa-pastories, Lamium amplexicaule, Malva neglects, Veronica persica, Sonchus spp., Galium tricornutum, Vicia vilosa, Silene conoidea, Fumaria officinalis, Convolvulus aevensis, Avena ludoviciana, Bromus tectorum, Euphorbia helioscopia, Muscari neglectum.