Spray application for brush
Earlier this spring I had about 5 acres of my woods (mostly the common poplar trees mixed with a few oaks and pin cherry trees) cleaned out and mowed with a brush hog. Most of this was a result of cleaning up storm damage in Todd County from last July. To make a long story short, I would like to spray something to kill or keep the brush down while allowing the grass to grow. Most of the brush is what I refer to as prickly pear, raspberry and even some poison ivy etc. I do not want to damage or kill any of the trees. I have heard that 2-4-D works but I worry about getting the spray on the tree trunks. Any suggestion. I do have a pull behind tank sprayer.
Todd County Minnesota
2,4-D is relatively weak on most woody species, so I'm not sure it would be worth the effort. Triclopyr is another growth regulator herbicide that is better on woody plants. It is sold under a variety of trade names (Garlon, Element, etc.). Crossbow is a premix of 2,4-D and triclopyr that is readily available at farm supply stores.
Any herbicide that will control the brush has the potential to damage the desirable trees. Proper sprayer calibration is important. Using nozzles that minimize small droplets that could move to the foliage of the trees is important. The bark of larger trees is a fairly effective barrier to absorption of the herbicide, but you should avoid as much direct contact of the tree trunks as possible.
Late spring applications made after the leaves of the target weeds are fully expanded is a good time. I would avoid making the application if significant rains are forecast within a day or two since the rain could move the herbicide down to the roots of the trees. The herbicides degrade relatively quickly so if you don't get rain within a week much of the herbicide will be degraded.