need help identifying lawn weed and suggestions for control
This stuff is starting to invade my lawn from an adjacent unmaintained area. I thought it was Japanese stiltgrass and tried a spot treatment with Acclaim Extra but that had no effect on it. (I mixed it at 1 ounce per gallon for a spot test, and used blue marker dye and "stickifier" to be able to monitor the area I treated). Can you ID it and tell me what would be effective on it?
This is Japanese stiltgrass. When weeds start to mature herbicides are not as effective on them. It is best to spray when the weeds begin to emerge. Also spraying when we are in a drought situation (which we were before all the rains came) is usually not successful because plants literally shut down during drought. And spraying when there is too much rain, which has been the recent case, is not good either. The third photo shows mostly Japanese stiltgrass, in this situation what kills it the best is glyphosate, which is a non-selective herbicide. Then the area would be ready to be reseeded with grass seed.
Another approach is applying a crabgrass preemergent about mid-March. Please see the following information from our website, http://extension.umd.edu/hgic/problems/japanese-stiltgrass