Neem is good, I believe. Isn't possible to just spray on the lower stalk since (I think) they have to travel down to the root system for moisture? Had the same problems, bastards reeked havoc on my plants. Since then, I heard that liquid seaweed spray will kill them. A Master Gardener said so. Hope others has some ideas also. What about a few Praying Mantis, that would be cool. Good Luck.