my greenhouse is only 10 feet away from my corn, never saw an aphid all last year except on the rose bushes out front.
the real concern will be bud worms, make sure to spray preventatively with BT while in veg.
aphids aint very clever. they rarely get inside a greenhouse unless somebody brings in a plant from outdoors. they sure do travel on the wind from corn though. when i grow corn i keep it well away from my tomatoes, and downwind as well. my area is heavy with peach aphids who really love tomatoes and cannabis, as well as tobacco white flies.
almost every plant eating bug can be controlled with liberal application of a hotpepper spray
in a saucepan on the stove, simmer
3 cups water
a large handful of peppermint leaves and stems
6 cloves fresh garlic finely minced (no powdered garlic! it doesnt work)
3 tablespoons (or more) cayenne pepper flakes
simmer for 45 minutes strain through a cloth (piece of old T-shirt works good) let cool and pour into sprayer addd 1 tablespoon biodegradable dish soap, top off sprayer with water put on a dust mask and ski goggles (super important) and SPAY EVERYWHERE!
wash hands thoroughly with soap before touching eyes mouth genitals or butthole (really really hot stuff)
it's non toxic (just spicy as hell) and washes off with water easily do not use on your buds unless youre a masochist. wash any produce before eating. and seriously, wash hands with soap before wiping your ass or holding your dick.
once a week will keep aphids slugs snails and whiteflies in check like a motherfucker.
Warning: may attract Hispanic, Thai, and Punjabi cuisine aficionados. do not store near salsa fixins or noodles and shrimp.