Paul: ROUNDUP [besides the non-labeled use issue] won't mix with chain saw oil since it isn't oil-soluble. Also, it sounds to be a very wasteful and not overly effective means of conducting such treatments.

Dave is correct by suggesting REMEDY [triclopyr ester, range & pasture label] for basal-bark and cut stump treatments. GARLON 4 is another name for the same formulation, but is labeled for industrial & forestry sites. However, the brace & bit boring method may be overdoing it.

REMEDY mixed with diesel at a 1:3 to 1:5 ratio [respectively] does a great job on virtually all woody plants, including huisache and mesquite. However, this mixture should never be applied to the targeted plant's foilage, as the diesel will dessicate the green leaf tissue before it has time to absorb and translocate the herbicide. Rather, simply apply the mixture to the trunk of the tree [basal-bark method].

For small-diameter tree trunks [< 5" in girth], there is usually no need to inflict any wounds to the bark, except for very thick-barked species. Diesel is an excellent bark-penetrator and will readily carry the herbicide component into the tree's cambium layer, which lies directly beneath the bark layer.

Larger and/or thick-bark species should be notched with a hatchet, machette or [for the "Tim Toolman" types] a chainsaw. These cuts or notches need only penetrate the bark and should be evenly spaced around the trunk's perimeter, thus allowing the REMEDY/diesel mixture that is subsequently applied to readily enter the tree's cambium layer.

Cutting or boring too deeply, as in completely through the cambium layer, will only allow the mixture to be absorbed by the non-active interior "wood" and will not improve the treatment's effectiveness at all.

As a rule, the herbicide mixture should be applied completely around the circumference of the tree's trunk, from about 18" up, all the way down to the groundline. If pre-treatment wounds are inflicted, they should be made as close to the groundline [aka "root-collar"] as possible, since this is the dormant bud-zone region, where resprouting is most likely to originate.

Similarly, cut-stump treatment should be applied only to the perimeter of the freshly cut surface of the stump, targeting the area just beneath the bark layer.

Hope this helps.
KD

Kelly Duffie
Cypress, TX