A home remedy
Use your hose and spray a good stream on the infected plant, if the plant can take the power of the spray. Do this 3 days in a row.
Try companion planting using mint, fennel, dill, yarrow, clover and dandelions which will attract aphid predators to your garden.
For long-term insect control improve your soil.
One easy way is to leave a small shovel in the garden. Collect a small container of kitchen vegetable scraps. Each day dig a small hole in the garden. Drop your vegetable scraps in the dirt. Chop them up with the shovel. Cover with dirt and you are done!
In small batches the material decomposes quickly. Remember - no animal scraps - if it came from the ground it can go back in the ground.