Aphids are small (1/8 inch long), soft bodied, pear-shaped insects that may be green, yellow, brown, red or black in color depending on species and food source. Generally adults are wingless, but some can grow wings, especially if populations are high. They have two whip-like antennae at the tip of the head and a pair of tube-like structures, called cornicles, projecting backward out of their hind end.
Note: As they feed, aphids secrete large amounts of a sticky fluid known as honeydew. This sweet goo drips onto plants, attracting ants and promoting a black sooty mold growth on leaves. Cars and lawn furniture that are under infested trees will also be covered with this sticky fluid.
This article provides useful tips for controling Aphids.
For curled leaves on citrus this is the cause: This will not kill your citrus. It is caused by the Citrus leaf miner. Leafminers are tiny caterpillers which is the larval stage of the Citrus Leafminer Moth. The larvae bore into the leaf shortly after hatching and live inside the leaf for only 3-4 weeks. After emerging, they oftentimes will curl the leaf and live inside the curled leaf until molting into a moth. The moth is usually actively laying eggs in the warmer time of the year starting in about June but can start earlier. This damage WILL NOT KILL your citrus plant but will make it very ugly. The moth will lay its eggs on tender emerging leaves when the tissue is very soft and easy to enter. To keep your plants clean you must spray on a bi-weekly basis directing the spray to the new growth. It is recommended that two different sprays be alternated.
Crapemyrtles suffer aesthetic damage because of the CMBS infestations. These bark scales may not kill the plants, but there may likely be a reduction in plant vigor, number of flowers, and flower cluster size. Infested plants typically leaf out later than healthy plants. Branches and trunks can be covered in the white scale infestation. Another striking symptom is the extensive amount of black sooty mold that may completely cover the foliage, branches, and trunks. However, do not confuse the honeydew and resulting black sooty mold caused by an aphid infestation with that caused by the crapemyrtle bark scale. Aphids are small insect pests that feed on new tender growth on the ends of branches. With a scale heavy infestation, there may be premature bark peeling. Often there will be more female adults congregated on the lower (and shadier) sides of branches. Here's an article to educate yourself on the history, causes, and treatment for CMBS.
Mealybugs are a common insect often seen on both outdoor and indoor plants. Their favorites are tropical plants such as hibiscus. They are small, oval and wing-less. These insects have long tails and are covered with wax that makes them look fluffy. Many times they are confused with some type of fungus. They have piercing-sucking mouthparts which they use to penetrate plant tissue and suck out juices. This can lead to chlorosis (yellowing of the plant), wilting and distortion. With larger infestations, these insects may cause stunted growth, premature leaf drop or death of the plant. Mealybugs are also known for secreting honeydew, which is a sweet, sticky substance on which a fungus called black sooty mold can grow.Tips for mealybug management: Use a high pressure water spray to dislodge mealy-bugs from the plant before moving indoors. For severely infested plants, it may be best to throw the plant away and buy a new one
Malathion 57% 2 tsp. per gallon (EXCEPT TROPICAL HIBISCUS), it will cause them to defoliate. Consider using products such as Captain Jack's, Horticultural Oil, Bifenthrin. The best thing for killing mealy bugs is malathion mixed with a sticker spreader. Apply three times ten days apart. Horticultural oils will work. Captain Jacks is an organic alternative. On a small infestation, use alcohol and water in a spray bottle.