Miscellaneous Ornamental Pests

Tiny, delicate dark flies that hang around potted plants are fungus gnats. These are adults of larvae that live in the soil, feeding onrganic matter. Cutting down on watering so the soil surface dries between waterings can do some good. Tilling the soil also helps discourage these flies from laying eggs.

Many different aphid species are important insect pests of plants. They include the green peach aphid, melon aphid, tuliptree aphid, giant bark aphid, white pine aphid and the rose aphid. Aphids are small (6 mm), soft-bodied insects, with piercing-sucking mouthparts that enable them to suck the plant juices out of plants. Aphids have a pear-shaped body, with a pair of cornicles (tube like structures) at the posterior end of their body, and long antennae. The cornicles excrete a defensive fluid which warns aphids of predators and other enemies. An aphid will secrete a substance called honey dew from their anus. This honey dew is attractive to ants, flies, hornets and yellowjackets. 

Aphids overwinter as fertilized eggs, and hatch as wingless females in the spring. The females reproduce wingless aphids until the plant is saturated with aphids. When overcrowding occurs, winged females will be produced and fly to another plant to form a new colony Aphids damage plants by decreasing the plant fluid, by the toxic action of their salivary secretions injected during feeding, by serving as virus vectors, and by reducing the plant's photosynthetic capabilities by the honey dew secretions left on the plant. Control measures include the use of beneficial insects, cultural practices and chemical means. 

Mealybugs are relatives of the scale insects. They have rather soft scales and soft bodies covered with a white powdery wax. The favorite place for mealybugs is where branching occurs on the plant. Mealybugs damage plants by sucking sap. The adult female mealybug may produce live young, or may lay eggs in a white fluffy mass of wax. The immature mealybugs, called nymphs, crawl all over the plant and onto nearby plants. Soon after they begin to feed, they produce white waxy filaments that cover their bodies, giving them a cottony appearance. As they mature, they become less mobile. Mealybugs excrete a fluid called honeydew, which coats the leaves of  the plant.

Control: 
Mealybugs are difficult to control since most pesticides won't penetrate 
the waxy shell.  For small infestations trim out infested area. 
Rinse your tools in hot water and let dry completely to make sure that you don't spread eggs from one plant to the next.

Home Remedies: These home remedies are diluted with water 
Dish soap and warm water (about 1 Tablespoon per pint) 
Rubbing alchol (and about 1/2 teaspoon soap)

Systemic pesticides: 
A systemic is a chemical taken up by the root system, distributed throughout the plant and to the foliage. The sucking insect ingests the poison.

Orange dog caterpillars feed on citrus. They are mottled dark grey to light brown, and are said to look like "bird droppings." If disturbed, two orange, horn-like projections emerge from the head and the caterpillar produces a pungent lemony odor. When mature the caterpillar is about 1 1/2 inch long. The adult is beautiful black and yellow butterfly called the giant swallowtail.
Orange dogs are potentially harmful to young trees only, older trees can easily withstand the loss of a few leaves. Orange dogs can be controlled on small trees by finding and crushing eggs and caterpillars. Most are controlled naturally by parasites and other natural enemies.

Spider Mites are tiny creatures, some less than 1/50 of an inch, most Spider Mites are too small to be seen without the aid of a microscope. 
They were named Spider Mites because they produce a fine webbing between leaves, a sign of  infestation. They suck sap from leaves and fruit, which causes yellow spots or stippling on the leaves. Their feeding  may cause deformations such as twisting and stunting of leaves as well. A mix of soap and water may be used to wash plant mites off leaves.  For large plants (Italian Cypress etc.), a morning rinsing of foliage with a forceful spray of water may help. 

Link:

• http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn006.html

The whitefly was considered only a poradic pest until the 1980s. 
However, possibly because of modern agricultural practices, today it is an extremely destructive pest of field, ornamental and greenhouse crops throughout the world. The whitefly possesses a short lifecycle of 18 to 30 days. Adult longevity is about 10 to 22 days. It attacks about 500 species of plants in over 70 families. The whitefly also serves as a vector for many plant viruses,
transmitting about 20 viruses which cause over 40 crop diseases. It produces a honeydew which promotes growth of sooty mold which interferes with plant growth. The whitefly is becoming increasingly difficult to control through chemical insecticides because of its rapiddevelopment of resistance and the fact that it most often inhabits the undersides of leaves which are difficult to spray. 
Link :

• Whitefly Control in Arizona: Developing a Resistance Management Program