What can I legally do if a neighbor piles up poop in my front door?

I am a tenant in a rental apartment for six years (tenant 30 years). In the immediate grassy area, our dogs have been allowed to poop. We have been able to come back in the day, or later to pick it up, and this has always been allowed. Since it is dark, rains, snows, is late and in a bad neighborhood, living alone, elderly, disabled and I have also been taking care of the yard for years, this has NEVER been an issue. Now, we have the same owner but a new manager and he is saying that since everyone else has to use a bag and follow the dog around, so do I. I am about ready to move out due to this. How can they just pull a rabbit out of the hat and suddenly change the rules? The tenants who live in the other buildings do not have the lawn right outside their door, but I do (within 3 ft) and so therefore they DO have to come over with a bag as we have had so many problems w it. A difficult tenant is now leaving dog feces outside my door for the last two weeks, in spite of me citing harassment and bullying laws. I know the owner wants me to stay as a tenant, and the manager enjoys having me tending (watering planting the lawn etc.) so I think he is just trying to stay out of it. The tenant who is leaving the stuff in front of my door is clearly mental, but I am getting ready to press charges. She says I have not a foot to stand on. I told her we have been picking it up later, and have been for 16 years and she isn’t even a manager (she thinks she is his "little helper") and can't just start issuing edicts out of nowhere. The manager just kind of hems and haws, and I'm afraid to push him on it or he will force me to follow her with a bag. I pick up mine at least twice a day, besides other dogs but no matter what I do, I am being scoffed at about tending the lawn, planting flowers, etc. and being harassed and the manager doing nothing about it. This is a section 8 HUD subs unit.