Thanks for your question. Well, this is really a three-step process. First, you need to identify the pests, which may be insects or pathogens (fungi, bacteria, etc.). After knowing what you have, you need to determine whether there are effective preventative or curative treatments, And only then you need you to determine if the insect infestations which have been there in past years have, for some reason, made them unsafe, unproductive or unfriendly in your environment. Have you ever used traps to see what you have? Have you used any type of sprays in the past? Effectiveness? What do the trees look like now? Have they produced in recent years, or are the fruit they produce full of insects? You could hire a licensed arborist to examine them, but they're going to need similar information to know whether they are salvageable or not.
Assuming that you might now know all of that, I suggest you read the following OSU Extension article on home orchards, which may get you started toward completing the analysis above: https://catalog.extension.oregonstate.edu/ec819/html. Write back!