A few years ago I saw on a tropical island some open ended poly tunnels growing salads and things that, in my own open air garden, are very heavily predated. They had a simple but very effective solution: they ran misters for a few minutes every hour. This made an environment that the plants thrived and insects left alone. And they lost very little water (on an island where fresh water was conserved generally) even though the tunnels were not closed at the ends. Fungus wasn’t mentioned when I asked about them. It was very simple tech level but I was struck by the smarts and knowledge behind it.