scaleinsect

Scale insects are a diverse group of small sap-sucking insects in the superfamily Coccoidea (order Hemiptera). They include armored scales (Diaspididae), soft scales (Coccidae), and mealybugs (Pseudococcidae). They feed by inserting piercing mouthparts into plant tissues and often form protective coverings, such as a waxy scale shell.

Most adult females are immobile after molting and remain beneath their protective coverings. Males, when present, are typically winged and short-lived. The life cycle usually begins with mobile first instar nymphs, called crawlers, which disperse to new feeding sites and settle. After settling, they molt into sessile nymphal instars and eventually lay eggs. Some species produce several generations per year, while others have fewer; overwintering stages vary by species.

Scale insects affect a wide range of plants and can cause significant damage through direct feeding and the production of honeydew, which promotes sooty mold and reduces photosynthesis. Heavy infestations stunt growth, cause yellowing and leaf drop, and can weaken or kill branches. They are important pests in agriculture and horticulture, and in some cases can transmit plant diseases. Natural enemies such as parasitoid wasps, predatory beetles, and lacewings help regulate populations, while ants that tend honeydew can protect scales from predators.

Management emphasizes monitoring and early detection, physical removal of scales, and chemical or biological controls. Horticultural oils and insecticidal soaps disrupt feeding and are often effective against crawlers. Systemic insecticides may be used for severe or persistent infestations. Biological control, including releases of parasitoids and conservation of natural enemies, is a common component of integrated pest management. Quarantine and cultural practices to reduce plant stress also help limit outbreaks.