Seeing Bugs With Microscope

I’m curious to know how come we are so careful with bugs on fruits and vegetables nowadays is it because we have the tools to see them i.e. microscope, or were Jews always this careful?

The bug needs to be seen with the naked eye. If you see something suspicious and you don’t know for sure if it’s a bug you can use an instrument to help you. R’ Elyashiv held that a minimum size of a bug is 0.2 mm