It is that time of year again. We are seeing the Poa annua plants on the greens and are trying to eradicate them. We have tried several chemicals, both pre and post emergent types in the past and we are continuing to look for new products and methods to prevent this plant from establishing itself. There has been a lot of research on the subject and the possibility for the plant to become chemical resistant. That is why sometimes you will see a plant that is healthy and green right next to a plant that is yellowing and hopefully getting smaller. Please be patient during this time of year and if you can, pull a plant or two while waiting on your group to putt out and close the void like a divot.
Here is one article of many on the subject -
Herbicide Resistance.