There's a difference between wiping out a virus that pretty much only affects humans, and wiping out an animal that's been present for millions of years and is

There's a difference between wiping out a virus that pretty much only affects humans, and wiping out an animal that's been present for millions of years and is firmly established as a food source for countless other animals. One has the sole effect of making humans healthier. The other is linked to far too many things to predict the outcome of. Considering dragonfly nymphs have mosquito larvae as a stable food source, it's safe to say that knocking them out will probably affect them. Then follow that food chain up (and down) and things start to get complicated.