Soft scale insects primarily feed on the leaves and twigs of plants, where their sap-sucking activity can lead to leaf discoloration, stunted growth, and in severe infestations, defoliation. However, the most noticeable and damaging effect of soft scales is the large volume of honeydew they excrete. This sticky substance coats plant surfaces and promotes the growth of sooty mold, which blackens leaves and reduces photosynthesis. The presence of ants, which are attracted to honeydew, is often another early indicator of infestation. Ferns, oleanders, and orchids are particularly sensitive to soft scale damage in ornamental crops.

In contrast, armored scales do not produce honeydew. Instead, they feed by piercing the epidermal cells of leaves and fruits, injecting toxic saliva that causes yellow, red, or brown patches. Over time, this damage can lead to leaf drop and a general decline in plant health. Despite their small size, both soft and armored scales can cause significant harm to a wide range of crops and ornamental plants if not properly managed.

Scale insects have a distinctive life cycle that begins when eggs hatch into tiny, mobile nymphs called crawlers. These are the only stage in the insect’s life when they are capable of active movement. Crawlers disperse across the plant in search of suitable feeding sites, typically on leaves, stems, or bark. Once they settle, they insert their mouthparts into the plant tissue and begin feeding on sap. Female crawlers remain permanently attached to the plant for the rest of their lives, gradually developing their characteristic waxy or hard coverings for protection. In contrast, male scales undergo metamorphosis into winged adults that do not feed. Their sole purpose is to locate females and mate. After mating, males die shortly afterward, while females continue to feed, mature, and lay eggs, completing the cycle. This life history, especially the protected and sedentary nature of the later stages, makes scale insects challenging to control.

Preventing scale insect infestations involves a combination of good cultural practices, careful monitoring, and environmental management, especially because their waxy or armored coverings make them difficult to control once established.

Start by inspecting new plant material thoroughly before bringing it into greenhouses or gardens, as scales often spread through infested cuttings, potted plants, or nursery stock. Isolating new plants for a few weeks can help prevent accidental introduction. Regular monitoring is essential—look for early signs such as sticky honeydew, sooty mold, or discolored spots on leaves and stems. Pruning and removing heavily infested branches or leaves can help reduce the population and limit spread.

Maintaining healthy plants is also key, as stressed or weakened plants are more susceptible to scale infestations. Manage ants around your plants, as they protect scales in exchange for honeydew and can interfere with natural control.

Good sanitation—such as cleaning fallen leaves, pruning debris, and dead plant matter—helps eliminate potential overwintering sites. In outdoor settings, promoting biodiversity and habitat for natural predators can provide additional, indirect prevention support. These combined strategies reduce the likelihood of scale insects becoming a persistent problem.

Preventing scale outbreaks can be effectively supported through the use of key biological control agents. Introducing beneficial insects early—before infestations become severe—helps keep populations under control and reduces the need for reactive treatments.

Cryptobug (Cryptolaemus montrouzieri): Known as the “mealybug destroyer,” this predatory beetle also feeds on soft scale insects. The larvae are especially effective, as they consume large numbers of scale eggs and young nymphs. Cryptobug works best in warm, humid environments.

Chrysopa (Chrysoperla carnea): The green lacewing larva is a generalist predator that actively hunts soft-bodied insects, including the crawlers of brown soft scale. Because Chrysopa is mobile and aggressive, it is particularly valuable during early-stage infestations or in dense plant canopies where pests hide.

Rhyzobug (Rhyzobius lophanthae): A specialist predator of armored and soft scales, Rhyzobug is ideal for long-term control in ornamental or tropical crops. Adult beetles and larvae feed on all life stages of scale insects, making them a reliable tool for ongoing population suppression.

The above biocontrol agents offer an environmentally friendly, residue-free approach to keeping brown soft scale populations in check.