Minor, definitely minor. While fungus gnats can be issues for plants, for particularly for some plants even in lesser numbers (poinsettia, for example), they're generally not a huge issue for others, and you reacted accordingly. Even for the plants where it is an issue, the numbers still have to be considerable.

The peroxide mix will kill most of the larvae, but you may have to repeat it (I find doing it once isn't always completely reliable). The trap (and spray, which is a little overkill, but no problem!) will kill the adults.

Seeing one or two fungus gnats buzzing about (I see one at the moment--ETA, in my home on one of my plants /ETA) is not of any great concern even with the most sensitive plants if you're on top of the problem and keeping an eye on it.

Later ETA: With the newly-added photos, that's not FG's. Although FGs may be a problem, something else is going on, too.

Whatever may be going on with your plants - and the photos are a bit skimpy providing that information - it is not a gnat issue. Adult fungus gnats only live for a week or so and do no feeding during this period so holes, bumps or discolored patches on the plant surface are not being caused by them. They are really just a nuisance factor only.

The gnat larvae could be damaging but generally only in large numbers and only from below the soil media surface....nothing obviously visual. They also thrive in damp, organically rich environments, which also tend to be NOT the kind of growing conditions typically offered to most cacti and succulents, as they prefer a sparsely organic, more mineral based media and drier conditions.

Not saying you don't have issues with fungus gnats....just that what damage you describe and what the photos attempt to indicate is not gnat related.

Clearer photos - most helpful when imbedded in the text, not linked - and more details about current growing conditions could provide greater insight.

gnats are a fair indicator.. that you are overwatering your plants ... let them near dry before watering again ... tell us how you water ...

it might also indicate your media is old.. and not working properly ... media is a water management system.. retaining what the plant needs.. and shedding/draining away un-needed excess ... when it gets old.. it doesnt do its job ... complicating how you water ... and if you ponder that for a few minutes.. you will realize different plants might need different media ... succulents will not thrive in media that water loving plants love ...

what are the result of the trap you created ...

there is absolutely nothing about houseplants.. to be terrified about ....

some say you are not a green thumb.. until you have killed every plant 3 times ... so you cant really become one.. if you are terrified of failure.. its how we all learned.. especially before the WWW

ken

Hi thanks for responding, Its been winter so I have not watered my plants much especially the Agaves and Succulents. I just watered them last week.

I've had the Agaves since August, they've grown quite a bit, it started with my Century Agave, the spikes on one leaf were gone about an inch and as you can see the edges are crumbling turning yellow brown. They seem to have what looks like mini scratches on some of the leaves. Yesterday I woke up to the donkey tail and succulent rose looking like this!

https://www.houzz.com/discussions/6087407/please-help-something-is-wrong-with-my-agaves-and-succulents