Spell for narrative purpose. I would like it to work mechanically as well.

I have a story I would like to present to my players and I have already started down the path with them but have not given them clear details of how this spell works.

The first thing I would like to work mechanically is that there is a blight that affects all crops in a large metropolitan area. People are struggling to get by and keep food on the table. This is going to take place inside Baulders Gate and its surrounding farmland/villages. The reality of this situation is that the main business is town that owns many market stalls and general stores has an underground faction that is causing this crop failure so that they can be the only business in town. Even food from the outside that has been imported into this area rots on shelves, in pockets. Only their food stays fresh.

The second part of this story is that there is an old wizard that the party has already encountered. He has a farm where he is for the most part a beekeeper to make mead for the local village nearby. He also grows fruits, lavender and vegetables for flavoring his mead and his own consumption. He has successfully kept the farm and village safe from the from the crop failure through some yet unknown means. I have hinted that he is quite a powerful wizard but his power is being drained keeping the farm and the village free from the curse or disease or whatever is causing this issue with the crops.

One friend of mine mentioned using Glyph of Warding but I am not sure that works as it seems like the glyph would disappear once it has been triggered. So it would just be a constant game of setting up new glyphs as I understand it.

The Glyph of Warding also does not explain how the faction would be causing the crop failure and crop failure in such a vast area.

I want this to work mechanically as well as narratively. How would ya'll accomplish this in 2024 Dungeons and Dragons terms? I'm sure it is possible but I feel like I've backed myself into a corner a bit. Help? hahaha