Abstract. Because of weeding, crops diminish substantially and, with strong weeding, crops can be much compromised. Horse thistle is a problem-weed in straw cereals and one of the most widespread and damaging weed species in Romania. Research was carried out over two years (2012 and 2013) in the experimental field of the Weed Science Department of the Didactic Station in Timisoara, Romania, in which we tested the effect of 11 post-emergent herbicides on horse thistle in winter wheat. The winter wheat cultivar we used was Glosa. The setting of the experimental field was done after the randomised block method: it was a monofactorial experiment with 12 variants and 4 replicas. In the first experimental year, we identified, initially, 98.56 weeds/m2, of which Cirsium arvense (L.) Scop. shared 7.91%, i.e. 7.8 plants/m2. In the following year, we identified, initially, 79.20 weeds/m2, of which Cirsium arvense (L.) Scop. shared 7.40%, i.e. 5.8 plants/m2. Overall, in the two years, the most visible reduction of weeding was in the variants treated with Buctril Universal (92.52-94.18%), Arrat (86.73-92.42%), Ceredin Super (90.18-91.07%) and Dialen Super 464 SL (87.40-90.63%). As for the exclusive control of the weed species Cirsium arvense (L.) Scop., in 2012, the best results were in the variants treated with Lontrel 300 (95.20%), (Arrat (94.49%), Iudith (91.37%) and Dialen Super 464 SL (90.63%). In 2013, the herbicides with the best performances in the reduction of horse thistle sprouts were Lontrel 300 (97.05%), Buctril Universal (93.51%), (Arrat (91.28%), Iudith (91.37%) and Dialen Super 464 SL (88.73%). The herbicide Cerlit EC had no visible effect on horse thistle – this is why we do not recommend it in the fields invaded by this species. Thirty days after the treatment, and more visibly sixty days after the treatment, the plants of Cirsium arvense (L.) Scop. tended to regenerate in all the variants shooting new sprouts that could not really compete with winter wheat plants that had almost reached maturity. All the tested herbicides were very selective for the winter wheat cultivar Glosa, with no visible symptoms of phyto-toxicity. Winter wheat crops in the experimental field were influenced, on one hand, by the climate conditions of the two years and, on the other hand, they correlated positively with the performances of the herbicides in the total control of horse thistle.

Keywords: Cirsium arvense L., weeds, winter wheat, herbicides, yields, selectivity

Presentation: poster