A survey of stem and root kill provided by commercial applications of four herbicides, 2,4-D, 2,4-D:2,4-DP, 2,4-D + dicamba and triclopyr applied on powerline right of ways through the 1989 growing season was undertaken. Eleven townships ranging from 35-27W4 north to 63-26W4 were sampled. Random samples of 10 trembling aspen and/or ten balsam poplar were taken per site. Wherever possible a total of 30 sprayed individuals per species per treatment constituted the total sample for a township. Since townships had been randomly chosen without prior knowledge of brush density, a full complement of 30 individual samples consisting of 3 replicates could not be achieved at all times. All the data was included for analysis. Sample size ranged from a low of 40 for diphenoprop to a high of 140 for triclopyr on trembling aspen. Data collection occurred from August through October 1991. Mix rates are indicated in the table below. All target brush was sprayed to the point of run-off with volumes ranging from 1,1OOL/ha to about 2,800L/ha. Two methods of application were employed, hose and gun and boom mounted nozzles. No attempt was made to separate the samples on the basis of application method or timing.
Efficacy comparisons of common brush control herbicides
|STEM KILL (%)||SPROUT FACTOR2|
|TREATMENT||Mix Rate/100L||Trembling aspen||Balsam poplar||Trembling Aspen||Balsam Poplar|
|2;4-D1||480g||86 b3||71 b||3 a||23 b|
|2,4-D:2,4-DP (1:1)||700g||98 c||99 c||35 b||0 a|
|2,4-D + dicamba||400g + 200g||82 b||74 b||9 a||6 a|
|triclopyr ester||288g||90 b||91 c||6 a||10 ab|
|Control||1 a||1 a||0 a||0 a|
1all herbicide treatments include NalcoTrol at 0.03% V/V
2number of sprouts X maximum sprout length
3Duncan’s Multiple range Test at 5% level
Diphenoprop provided excellent stem kill of both trembling aspen and balsam poplar. Considerable and significant suckering of trembling aspen occurred while suckering on balsam poplar was virtually non-existent in spite of excellent top growth control. Triclopyr provided very good stem kill of both poplar species. Root suckers were found for both poplar species but were not significantly greater than the control. Fair to good stem kill was provided by both 2,4-D and dicamba plus 2,4-D. Root suckering was not significant for the dicamba mixture but the 2,4-D alone resulted in significant root suckering of balsam poplar.