|I noticed some kind of fat brown worm like insect on the leaves of my little Satsuma tree. They lay on the leaves and destroy the orange buds and leaves.|
|I can't tell from your description of the pests just what they might be, but a product called Bt (Bacillus thuringensis) is registered for use against caterpiller type pests. It's a stomach poison so the critters will eat for a while before the bacterium affects them. Best of all, Bt is not harmful to other insects.
Hope this helps!