Aphids are nearly all female (rare males have wings), are born pregnant, are parthenogenic (they don't need to have sex to reproduce), and give live birth to miniature HUNGRY adults...no egg or larval stage! So in a very short time they can cover the growth tips of okra, roses and many other plants and literally suck the life out of them. Short term control can be achieved by blasting them off the plant with a garden hose spray nozzle, spraying them with a Kirk's Castile soap solution (see recipe on an early page of the blog archives), and letting native ladybugs and lacewings colonize your yard over a couple of years after you cease using pesticides. But an excellent long term approach that has done wonders for me and landscape clients since the early 90s is to buy mail order the eggs of the TINY, non-stinging Trichogramma wasp that over two years colonizes a landscape as the female wasps lay their eggs INSIDE the aphids. When they hatch they eat their way out like the monster in 'Alien', leaving behind a hollow husk.
For years I and my clients have bought them from Gardens Alive. I prefer the "combo" that has the eggs of two species, Trichogramma pretiosum to protect plants up to 5 feet tall (roses, most crops, low shrubs) and Trichogramma minutum for tall shrubs and trees. For about $23 you get 24,000 eggs in three bi-weekly installments. I feel that spring is best but if you order now you might get a population established before winter. Order them at:
www.gardensalive.com or at: 513-354-1482