[MAIPC] Japanese Stiltgrass and horticultural vinegar

[Richard Gardner]

I am in the process of studying the effects of horticultural vinegar on Japanese Stiltgrass (Microstegium vimineum). I used a 2 liter Futone pressure sprayer like one I would use to spray issues in our small yard with 30% and 15% vinegar (acetic acid) on two small sections of a remote trail we use which have dense Japanese Stiltgrass. The experiment is only 9 days old. The stems were 2" to 3" tall.
What I am seeing so far is that the 30% acetic acid was more effective than the 15%. The photos show about 50% "browning" of foliage. The issue appears that like in many foliar applications the key to success in killing the Japanese Stiltgrass with either concentration is the amount of the foliage the spray wetted. I am thinking that a day where the grass is wetted with heavy dew or fog is the best time to spray as it will spread the acetic acid better on the foliage and stems than dry days.
I do not have the ability to do a water control or try standard household vinegar at 4.5% acetic acid due to equipment limitations. My negative control is the untreated stretches of trail with Japanese Stiltgrass.
With better equipment such as a backpack sprayer, which is on order, I a certain the preliminary results would have been better. I intend to redo this experiment as soon as the backpack sprayer arrives.
This will be an ongoing experiment borne of necessity if we expect to use some of the local trails.*
*The main issue we have with Japanese Stiltgrass in this situation is that the taller the Japanese Stiltgrass grows the harder it is to see footing, especially on rocky trails like this one. If we expect to use this trail safely we need a clear path through the Japanese Stiltgrass. Last year I used a weed whip with some success when the Japanese Stiltgrass was mid-calf high.
Another issue I have is that our dog is often on leash which means I have to watch my footing, look for other dog hikers and handle a 15" (homemade) leash. Even though this is a remote and lightly used trail we have encountered dog hikers several times.
We use this trail mainly to avoid other more heavily used trails where we have less control in the number of people (and dogs) we encounter. In this age of COVID and living in a bleeding red section of Pennsylvania where few are vaccinated the fewer people we encounter the better.
Even though we are vaccinated we are still being very cautious in our encounters with other people. The fewer people we come in contact with, especially people we are uncertain of their vaccination status, the better.
                                        Richard Gardner
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