question about canceling rental lease due to roach problem

Sorry that I can't type chinese well at work.

We had a rental duplex, one tenant moved out 7/1.  We signed 1-yr lease with new tenant on 7/10, agreed to move in on 7/14.  When sign contract, we see some cock roaches, so we hired pest control to do cock roach control spray on 7/12.

Tenant found a lot more roaches on 7/13 and requested additional pest control service, so we signed a 1-year agreement with pest control service for monthly control.  Pest control did another spray on 7/17, and said tenant will still see some roaches until after 3-4  months.  We verbally agreed new move-in day of 7/27.

But now tenant didn't feel comfortable to move-in any soon, she wants to set move it day to 9/1. 

We can not affort to lost one month rent, so we want to cancel the agreement and find other tenants who don't mind little roach problem, such as tenants with little pet.  And we still provide 1-year pest control service.  We are confident that we can find other tenant to move-in by August.

Is it possible to cancel the lease agreement?  If tenant doesn't want to cancel the lease, can we still collect rent starts 7/27?

Thank you very much.