Aphids are small sap sucking destructive pests (about .04 to .39 inches) that feed upon cultivated plants. Their body color can range from green, black, brown, pink or clear. As they feed upon a plant, aphids can transmit plant viruses to the plant. These viruses are powerful enough to occasionally kill the sieged plant. Plants that are under attack by aphids may demonstrate such symptoms as yellowing, curled leaves, browning and wilting.