Advice and input please... My orange tree is thisclose to getting chopped down and replaced w/a crape myrtle or Teddy Bear magnolia. Though I'm worried about acting too hastily, I'm equally worried about having an uncontrolled whitefly/citrus blackfly infestion throughout my garden. Please chime in!

About two months ago, I noticed these black egg-like things on the bottoms of the leaves (the photo attached is not mine but this is exactly what 20-25% of my leaves look like right now). My extension office diagnosed these as whitefly pupae. I've also observed some tiny, white moth-like things flying around my lawn (day and evening) but not sure these are the dreaded beasts. It just makes me uneasy thinking of the damage that could be happening all around. Anyway, I sprayed the tree with Fertilome's Triple Action fungicide/insecticide two weeks ago but the black specks are still there--no change. A hard spray with the hose doesn't budge 'em either. Basically, I have no idea if the treatment has had any beneficial effect...or even what signs to look for.

Background on the tree: I inherited it with my house--it's an unknown variety planted by my parents and could be over 15 years old. It's an attractive tree that provides good shade for an A/C condenser and small bathroom window. It's probably about 12-14 feet tall, has a nicely shaped habit, and produces lots of blah, thin-skinned fruit that no one eats. The leaves are full and green and to the casual observer it looks healthy enough. But there have been other problems, including sooty mold a few years ago, immature fruit splitting open and rusty colored skin on the fruit. The sooty mold eventually cleared up after many, many months of benign neglect by yours truly. I'd probably go that route again but I've taken more of an interest in gardening and don't want to risk my plantings from this past season.

I know someone who can remove the tree and grind the roots for a very reasonable price. But I'm torn! Is there something I haven't tried? Thanks so much for reading!