My son is extremly defiant and my husband doesn't help. What should I do?

I have a three year old son. He's been very difficult lately and doesn't want to listen and has been very sy. My husband is a firm believer in the whole, spare the rod spoil the child, mindset. I don't feel that every bad behavior deserves a . I decided to try the behavior modification chart and do the reward system with stickers. My son is doing really good and loves the chart. My issue is my husband refuses to do it too, saying he isn't a kindergarden teacher and refuses to do so. He says if our son misbehaves, he'll just get ed. Am I thinking wrong here or should this be a group thing, not just a mommy and baby thing?