No, it's not a fungus. It looks like leaf miner damage. We don't know where you are located so nobody can tell you which species it would be.

I agree. Looks like leaf miner. How extensive is it? If just a here and there, and occasionally, I wouldn't do anything but clip off the individual damaged pieces. If it is regular and pervasive at a certain time of year, you'd need to spray with a systemic insecticide BEFORE the next onslaught. (The damage is not a growth per se, but is destroyed tissue. Leaf miner is a larval stage insect hatching inside the leaf and eats away within it. It's very hard to deal with without, essentially, poisoning the whole plant.)

ere's my 2 cents: leaf miners. They burrow inside the leaf and that damage you see is thinned leaf which is drying out. Spraying insecticide won't work. unless it gets very very bad, it won't kill the plant. After 20 years of Florida gardening, I've resolved to let nature take it's course. Keep your ecosystem healthy (avoid pesticides, herbicides, plant some native plants and let the frogs, toads, dragonflies, lizards, birds, etc. do their thing.

"Spraying insecticide won't work." As I mentioned, it is about timing and type. It must be a systemic insecticide and it must be applied prior to the larval hatching and their eating damage. Applying to plants is not going to cause harm to the ecosystem, in spite of what so many well meaning people believe, as it has temporary effectiveness and breaks down into harmless substances through the action of sunlight, weathering and decay. For a short while it's going to cause harm to the insects that eat the plant.