Scales are armor covered insects often black or brown in color. Their shells are oval to circular shaped and convexed (curved like a contact lens). The adults don't move so they will been seen to be stationary in adult stages.
Symptoms and Damage:
Scales are sap-sucking insects so the effects will be similiar to other plant sucking pests. The leaves will become discolored and wilted, eventually dying and falling from the plant. Like other sap-suckers scales excert honey dew which forms a sticky base for molds to grow so you may see black sooty mold or other types on the leaf and stem surfaces.
Habitat and Life Cycle:
Most scales involve both male and female in the species and reproduce accordingly. The female lays fertilized eggs under her protective "scale" until they hatch.
The hatched scales, called crawlers at this stage, venture off in search of a suitable feeding location. When a spot has been found the crawler inserts its mouth organs into the plant and begins feeding.
After several molts the female crawlers loses its legs and is no longer mobile. It will spend the remainder of its life attached to this one spot. The crawlers that became male develop a set of wings and begin to search for a immobile female with which to mate. And the whole cycle begins again.
Control and Prevention of Scale
There are many benefits to avoiding chemicals when dealing with insect invaders. The harsh chemicals in some insecticides may cause more harm to an already injured plant not to mention the possible harmful effects to you or your loved ones.
✔– First choices for attempting insect control.
✔– Used when green don't solve the issue.
✔– Only use when blue options have failed and the plant cannot be discarded.
Prevention✔- Planting species of plants near effected species is a good way to promote natural predators to visit and destroy scale infestation. For example planting flowering plants will attract bees, wasps and other natural predators of scale. As always regular inspection and proper maintenance of your plants go a long way in preventing any kind of infestation.
Manual✔- Pruning infected sections of the plant is a great way to ensure removal but the infestation must be recognized quickly. Scale may be removed manual using a toothpick, soft toothbrush, cotton swab dipped in rubbing alcohol or by rubbing with your fingers on more hardy plants.
Organic✔- Soap Spray sprayed on the leaves and stems, followed by a rinse in clean water may be enough to curb a minor infestation.
Biological✔- A number of parasitic wasps and beetles are available to commercial growers but may be difficult to locate for the average home gardener.
Chemical✔- A number of different oils and sprays are effective on all stages of scale life cycle. Consult your local garden center or nursery for the best options to you.
More information on Scale:
Wikipedia - http://en.wikipedia.org/wiki/Scale_insect
Gardening How To - http://www.gardeningknowhow.com/how-to-control-plant-scale.htm