These things caused me the biggest headache trying to get my moringa trees going. I thought it was rabbits considering how much would disappear overnight. The closest thing I have found to a solution is to have a bunch of whatever you are trying to grow, enough that they can't eat it as fast as it recuperates. They seem to eat one thing for a while and then move on to something else.
And isn't there something to do with aphids in their nest involved? Some sort of symbiosis?
I'm not sure about the aphids. I read that the fungus grows and they eat that. If one of the leaves starts killing the fungus, they will stop eating that leaf and find something else. Maybe a fungicide on all the moringa trees?