Aphids attack most green plants, usually in spring though they may be present throughout the growing season. While they are usually white, there are also blue, pink, brown and yellow varieties of the insects. They have piercing mouths that latch onto the fleshy parts of plants, usually the leaves or stems, to suck out the juice. While aphids may not cause direct damage to plants, they transmit viruses and diseases which can lead to plant death. Killing the aphids on green plants is necessary to prevent this.
Inspect the plants regularly during the growing season for signs of aphid infestation. Look on the underside of leaves and the stem of the plant. Use a magnifying glass to aid inspection, as some aphids are quite small.
Spray plants down with a heavy spray of water, concentrating on the infested areas, if minor infestation is present. This washes the aphids off the plants. Spray in the mid-morning to early afternoon so the plants have time to dry before nightfall, as wet plants are prone to mildew and fungus.
Mix 3 tbsp. of liquid dish soap with 1 gallon of water. Place in a spray bottle and spray down the infested areas of the plants to kill the aphids. Rinse off the soap one to two hours later so it doesn't form a film on the leaves that may inhibit plant respiration.
Apply an insecticide formulated for aphids if infestation is severe. Follow label instructions for application instructions and amount.