Q.How To Get Rid Of Tiny Caterpillars Eating Royal Empress Leaves
I check the tree almost daily. Many times I have to remove and squish tiny green caterpillars and scrape egg nests from the underside of leaves. Have tried neem oil, diatomaceous earth and caterpillar spray. Any one of these seem to work for a short period (1-2 wks) but the problem returns.
Certified GKH Gardening Expert
Have you tried Bt? It is specifically for caterpillars and is an organic way to eliminate caterpillars. You may have the same problem though, it will need to be reapplied to the foliage after rains.
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/using-bacillus-thuringiensis.htm