If an IPM plan is required, developers should be informed during the development review process. It is then their responsibility to submit, and comply with, a plan. If the land is then sold, it is their responsibility to communicate the need for the new land owner to abide by the plan.
If you own an individual parcel of land that requires a site plan review and no developer or previous owner has submitted an IPM plan, then it is your responsibility to do so.
If you purchase a property that already has a plan, then it is your responsibility to abide by the plan.