Non-toxic pre-emergent herbicide for Japanese Stilt Grass
I have large masses of Japanese Stilt Grass growing in parts of my yard. I would like to use a natural product made from corn gluten meal to kill it as it germinates. This is supposed to stop root development of germinating weeds. The catalog says that it works on perennial, broad leaf and grassy weeds, including crabgrass, creeping bent grass, smart weed, dandelions, red root, pig weed, purslane, lambs quarter, foxtail, barn yard grass and Bermuda grass. Is there any reason why this wouldn't work on Japanese Stilt Grass too?
Corn gluten has not been proven by research to be a very effective preemergent. At minimum, it will provide some control of crabgrass and some broadleaf weeds if weed pressure is low.
It also is a nitrogen source, which makes it a fertilizer and it must be counted in your lawn fertilizer quota for the year. Applied at the recommended rates on the bag for use as a weed preventer, it exceeds the amount of nitrogen permitted in Maryland by the Maryland Lawn Fertilizer Law (https://mda.maryland.gov/Pages/fertilizer.aspx). So for these reasons, we do not recommend using it.
We agree that Japanese stiltgrass is an invasive weed but a conventional preemergent would be more effective in preventing it. The following page outlines what our recommendation is for residents of counties other than Montgomery County:
Replies to lawn weed control questions from people in Montgomery now need to allow for the Montgomery County Pesticide Law. The Court of Special Appeals of Maryland recently ruled in favor of the law restricting the use of pesticides on private lawns and childcare facility grounds in Montgomery County. This is a new law and Montgomery County officials are still deciding on how to proceed. The Montgomery County Department of Environmental Protection has information about the law and organic lawn care on their website
We also have some resources on our website that may be of help to you:
Organic lawn care - https://extension.umd.edu/hgic/topics/organic-lawn-careTips for Lawn Weed Prevention and Management - https://extension.umd.edu/hgic/topics/tips-lawn-weed-prevention-and-management