We do not recommend applying Tordon RTU Specialty Herbicide or any herbicide when temperatures are below 55 degrees. Tordon RTU Specialty Herbicide does work best on freshly cut stumps or fresh cuts in trees.
Tordon RTU Spray is not labeled for Walnut Trees therefore we cannot confirm if it would be effective in killing the tree. Black Walnut tree roots can spread out 50-80ft from the tree and are known for resprouting. The most recommended treatment is to cut the stump as low to the ground as possible and apply a product with the active ingredient Glyphosate directly to the freshly cut stump. Direct stump treatments is going to be your best option and will take several months and maybe longer since this tree is so old. Roundup QuickPRO has Diquat as 1 of the 2 ingredients works for a faster knockdown and absorbs throughout the root system better. Drilling into the stump is also sometimes done for the herbcide to absorb quicker into the tree.
Tordon RTU Specialty Herbicide states to not apply during the spring sap flow on the product label.
