Here’s how I think the Fungal Infection grows.
1.First, a fungal spire spawns in the map.
2.From the spire, spores come out.
3.Spores become Young Fungaloids.
4.Young Fungaloids become normal Fungaloids.
5.Normal Fungaloids produce Spores.
6.Go back to step 3.
I think you need to destroy the Spire (with some serious firepower) and then kill as many of them suckers as you can. If you miss one, they will grow back, although since the Spire won’t return, their numbers won’t get so out of control.
I recommend molotovs, LAWs and a good car.