1) Put a fence around the corn! Be sure that you use posts that a squirrel can't climb, and situate the corn patch at least 15-20 feet from other trees and fences. Even chicken wire will work(and is pretty cheap). Fence should be at least 5 ft. tall-- most squirrels can't jump up from the ground, but who knows, they might MUTATE to get to that corn;-) .
2) Aphids are easily controlled if you get to them RIGHT AWAY when you first see them. In the following order:
a) sharp spray of H20 from the hose-it knocks them off the plant and they don't fly and have trouble climbing--although the ants that tend them might CARRY them back--aphids are known as "ant's cows"; the ants literally "milk" them for the honeydew.
b) 1 teaspoon dish detergent per quart of water in high pressure sprayer-THIS WORKS!
c) Insecticidal soap(available at garden centers) according to directions.
Get more information on IPM(integrated pest management) from your local University Ag. Extension, they're a goldmine of info. And most of them are STARTING to realize that pesticides are POISON!
Diane in St. Paul MN