Do you do it because it is necessary?
Remember they are creation of God.
I've thought about this a lot. The fallen world is death. Death is the answer to everything. Squash bugs, kill relationships that stress you out by leaving it, and so on. When we think of the dominion mandate from Genesis, we see it in terms of death. Kill the enemies. American Christians believed in the dominion mandate for North America. Sometimes they negotiated Native Americans to move to new territory. Sometimes they slaughtered the resistance.
But what did God mean when he told Adam to have dominion before the fall? How do we have dominion according to life and not death? I am still meditating on the topic.
However, getting back to your specific question, insects are necessary to ecology. They are the gardeners of God. They break down waste matter and turn organic material into soil. They also pollinate plants to increase plant reproduction. So, yes, they are God's creation.
Simply being God's creation is not enough, tho. All creation has been damaged by the fall of man. Thorns did not exist in paradise, but they grew as a consequence of man's sin. It is not likely that any creature was poisonous either, but some changed as a result of the fall.
So, to answer your question. Yes, I kill insects in the house, and depending on the circumstance outdoors, too. Ever try growing a garden without managing insects? Ever get stung by a wasp who built her nest in your door frame?
Yes, life is sacred, but not all life is the same. It was God who told Noah to eat animals after the Flood. Probably before that it was not done. But after the Flood it became necessary until vegetation regrew. Insects have very short life spans but reproduce abundantly. If moths get into your pantry, they will lay eggs you can not easily see and multiply, devouring your food. If you don't kill them, they will spread and eat your clothing in your closets, as well.
New Age thinking and environmentalists affects the thinking of some Christians. California burned badly last year. One big reason is because forestry management was stopped and deadwood built up beneath the forests providing abundant fuel for forest fires. Trees have to be pruned and trim to grow healthy. If we don't do it, then it will happen naturally with either strong winds, fires, or both.
Tarzan was right. Kill when needed, but don't needlessly kill. When Jesus returns, then we will truly understand how to have dominion based upon life and not death.