Efficiency of Two Commercial Forms of Clopyralid at Different Doses in Controlling Canola Weeds

In order to compare two commercial forms of clopyralid (30% SL) under the trade names of Lontrel and Watch and their high dose effects on canola, an experiment was conducted in randomized complete blocks design with 12 treatments and 4 replications in Fars and Khuzestan provinces during 2008-9. Treatments included post-emergence application of Lontrel and Watch at 0.6, 0.8, 1, 1.2 and 1.4 L.-ha., pre-emergence application of quinmerac+metazachlor (Butisan Star, 42.1% SC) at 2.5 L.-ha. and weed free check. All plots were sprayed with 0.75 L.-ha. of haloxyfop-R-methyl ester (Galant Super 10.8% EC) post emergence against grass weeds. Results indicated that both types of clopyralid were safe on canola up to 0.8 L.-ha. One L.-ha. of clopyralid caused slight damage to canola, but soon recovered and did not affect yield, while better control of weeds was observed. Control of dominant weeds (Cardauus pycnocephalus L. and Polygonum aviculare L.) in Fars province, by one L.-ha. of both commercial forms of clopyralid resulted in highest canola yield increase (28%). Control of dominant weeds in Khuzestan, including Silybum marianum L., Ammi majus L., Melilotus officinalis (L.) Pallas and Malva spp., by one L.-ha of both commercial forms of clopyralid increased canola yield by over 200 per cent.