Yeah, I had some aphids on my potted lemon tree one summer, and I got ladybugs, released them, and they promptly flew away into my neighbor’s yard and I never saw any on my lemon tree.
Ended up having to carefully spray everything with that insecticidal soap, which worked very well, but was a pain.
Jesus Tapdancing Christ, do NOT do this! Sycamores flower and bees are their preferred pollinators so this is like setting up giant bee killing stations. You might not like messy aphids on your trees, but you’ll like living without over half the plants you eat on the regular once the bees die off and there’s noting to propagate them much, much less. I can’t wait until someone figures out we need to ban the sale of that crap.
For those that have tried ladybugs, did any of you try releasing them at night? I heard* that ladybugs don’t like to fly after dark. So, if you release them at night they’ll at least have one meal on the aphids before they fly away. Might even stick around once they’ve learned there’s a rich food source there.
Do birds eat aphids? Maybe a bird feeder near the tree might help.
That’s a numbers problem. You bought so few ladybugs that they were able to disperse around the neighborhood enough to be low density in your yard. What you need is to buy enough to saturate their entire flying range from your yard, turning your neighborhood into a nightmarish writhing sea of cute little red and black bugs. So order hundreds of thousands at a minimum.
(I bought a bag once–I think maybe 1,000? They seemed pretty effective, at least in the short term. A few photos of them in action are in this album.)
Try to get the larvae instead. They eat more and can’t fly.