Scale insects

Scale insects are a large group of pests belonging to the order Hemiptera, specifically the suborder Sternorrhyncha. They are small insects that primarily feed on plant sap, a behavior which can damage a wide variety of plants, including crops, ornamentals, and trees.

Description

Scale insects vary dramatically in appearance and size, typically measuring 1 to 2 mm in length when mature. They are named for their scaly protective covering over their bodies, which can be either hard and armor-like or soft and waxy. This covering helps protect them from predators and environmental conditions while they are feeding.

Life Cycle

The life cycle of scale insects includes several stages: egg, nymph (called a "crawler"), and adult. The females generally remain stationary, losing their legs and antennae as they mature, and often become permanently attached to the host plant. Males, on the other hand, may develop wings and are free to move about.

Ecology

Scale insects are found worldwide, with over 7,000 species described. They can have a significant impact on their environments by weakening plants through their feeding. Some species also produce honeydew, a sticky liquid waste that can lead to the growth of sooty molds on plants.

Economic Impact

Scale insects can cause considerable damage to agricultural and horticultural plants. They are difficult to control due to their protective scale cover. Management strategies include biological control using natural predators, such as ladybugs and parasitic wasps, and chemical control through the use of insecticides.

Systematics

The superfamily Coccoidea is divided into several families, including:

• Asterolecaniidae (pit scales)
• Coccidae (soft scales)
• Diaspididae (armored scales)
• Eriococcidae (felt scales)
• Margarodidae (ground pearls, giant coccids)
• Pseudococcidae (mealybugs)

Control Methods

Control of scale insects can be challenging due to their protective cover and the waxy substances they excrete. Integrated Pest Management (IPM) strategies are often recommended, combining biological, cultural, and chemical methods to manage scale insect populations effectively.

See Also

• Pest control
• Integrated Pest Management
• Biological pest control