The field trial was conducted at the experimental farm Kolíňany (south-west Slovakia) in 1999-2006. Experimental farm is situated in warm and moderate arid climatic region with altitude of field from 180 to 310 m. The average annual rainfall is 580.0 mm. The average annual rainfall during the growing season is 320.3 mm. The mean annual temperature is 9.6˚C. The mean temperature during growing season is 16.3˚C. The soil is Orthic Luvisol with loamy texture with different thickness of humus layer (from 0.23 to 0.45). Winter wheat was growing on minimum 10 large scale field range from 30 to 50 ha. An actual weed infestation was evaluated before application of post emergent herbicides and 3-4 week after application of herbicides and third evaluation just before harvest with concordance to International scales of EWRS. Screening of each field was made on the quadrant of 1 m 2 area by counting method with four replications. The four randomly established sample quadrants were situated minimally 20 m from field margin and apart each other, respectively. The dominant weed species in winter weeds field were as follows: Elytrigia repens, Galium aparine, Tripleurospermum perforatum, Cirsium arvense, Fallopia convolvulus, Lamium purpureum, Stellaria media, Capsella bursa pastoris, Thlapsi arvense and Viola arvense with low to medium infestation level. Total weed density was high.The different level of seasonal dynamics. Mostly in all species generally the declination of infestation level and weed density was noted at the end of evaluation period. The increasing level of infestation was noted by Tripleurospermum perforatum, Fallopia convolvulus, Stellaria media and Capsella bursa pastoris. The higher actual weed infestation was noted in 2003 and 2004. These evaluated years were characterised by wet condition with normal up to warm temperature and spring was characterised by normal precipitation and temperature condition. The changes of active ingredient of herbicides significantly influence the composition of weed flora for instance decreasing of trifluralín support the Stellaria media infestation and Lamium spp. The weed control under threshold level is important also for subsequent crops.

weed infestation; winter wheat; herbicides

Presentation: oral