Weed control measures for controlling the density of Canada thistle (Cirsium arvense (L.) Scop. in wheat (Triticum aestivum L.)

Canada thistle [Cirsium arvense (L.) Scop.] is a major weed in semi-arid areas of Punjab, Pakistan. studies were conducted during 2010-11 and 2011-12 at University Research Farm, Chakwal road, Rawalpindi to study Canada thistle control and density dynamics in wheat grown under contrasting environments and diverse cultural, mechanical and chemical thistle control measures. Experiments were carried out in randomized complete block design with four replications. Canada thistle density was monitored at five stages during wheat growing season. The results revealed during wet winter season, Canada thistle was effectively controlled (90-97%) when dry-season tillage was integrated with fertilizer placement in a strip along crop row and with single application of full dose of clopyralid. The drier winter season witnessed significant thistle control (91%) with half dose of clopyralid when integrated with dry-season tillage, fertilizer placement followed by inter-row cultivation and remained at par with experimental treatment where full dose of clopyralid was applied. The thistle dynamics data showed that higher thistle re-sprouting during wetter environment decreased efficiency of thistle control in cultural and mechanical control measures applied either in integrated or sole fashion. (author)