You can overseed and use pre-emergent at the same time... but overseeding
for fall, then applying after the grass has come in, is fine.
Here, we need to apply pre-emergent no later than the end of January.
Here's the link to the cooperative ext in Maryland
http://extension.umd.edu/gardening/index.cfm
Great source of info
Nicole in CA
"Keith Corwell" wrote in message
...
Hi all I am thinking about doing some overseeding this fall.

I live in mid Maryland. My question is can I use a preemergence next
spring to fight crab grass