A lot of my trees are taking damage right now from insects. Mostly mango, but some others. I don't have any pesticides on the lawn and the ants got out of control. I could see aphids or white scale or thrips on a lot of the dead leaves of my Canna Lilies and some coconut palms that are buried in undergrowth. I can see tiny white insects flying around before sunset and lots of moth and caterpillar activity.
I ordered some organic insecticides (Pyrethrin and Spinosad) and applied them to the affected trees with a pump sprayer. I also started spraying the ant mounds with the pyrethrin. It works great but doesn't last that long. I'm not sure exactly which insects I have compared to you but I can see improvement from the spraying already and I will continue to hit the affected trees until it's gone.
Tanglefoot on the tree trunks also helped but that's not enough on its own. I also got caught up on my fertilizers, iron and calcium. I tried to cover all the bases where somebody with more expertise might be able to isolate one factor.
