My neighbour has a drumstick tree which seems to be infected by some caterpillars. I don't know whether they have sprayed some medicines or not but all of a sudden nearly a dozen of them have come in to my garden. They have almost ripped the leaves of a croton overnight and are now spreading to other plants. I tried spraying some rogor but it doesn't seem to be helping.What other pesticide can I use? Any help is truly appreciated.