Our neighbors have roadside aster in their yard. I was able to eradicate it from our yards last year.

I don't recall what I used at that time, but did a web search and Neil Perry recommends 2,4-d. This is a post emergent that should be used in early spring and early fall.

We are outside these time frames. Is there something that cam be used as a preemergent?

I have no insight into how to get rid of that…as my yard can attest…,but that stuff sucks!

https://www.lowes.com/pd/Spectracide-Weed-Stop-For-Lawns-32-fl-oz-Crabgrass-Control/1000783760
Active Ingredient 2,4-D, dimethylamine salt