There are aphids on the pepper plants in the greenhouse and I've tried garlic to no avail. I seem to remember that marigolds and aphids don't get along.
Are Lemon Scented Marigolds an Aphid Repellent?
Any of the African or French scented Marigolds act as an insect repellent. I use marigolds all over my garden for that reason. But you do need to make sure you have picked a variety that has scent! Some of the newer hybrids are scentless, pretty but not particular practical for that use.