In New York state, must a broker (or landlord) disclose that a deceased person's ashes are buried on the grounds (of a country house for rent)?

The NY State Dept of Health says
"You may also dispose of the cremains in any manner that complies with local health department or other regulations."
... so legally, it's a local issue.

I couldn't find an answer addressing whether an owner or agent is required to disclose, but my R/E knowledge leads me to think "No"

Even if someone "broke the law" in burying them there, I don't see that a case could be made that it's knowledge would affect the transaction; That is, be a detriment that a new owner needs to be aware of.

If you don't get a firmer answer, try the NY City Dept of Consumer Affairs. They've got some info here, but don't say what is acceptable for ashes.