African soft scale

The African soft scale, scientifically known as Coccus africanus, belongs to the Coccidae family within the Hemiptera order. This pest exhibits significant sexual dimorphism.

Adult females possess an oval, slightly convex body of a brownish or yellowish-brown color, which attaches firmly to the plant surface. They lack a true shield, as the hardened cuticle of their body provides the necessary protection.

First-instar nymphs, commonly referred to as crawlers, are highly mobile and pale yellow, allowing them to disperse easily across the plant or be carried by the wind.

Males are rarely observed; they are winged and have reduced mouthparts, meaning they do not feed and their sole biological purpose is to fertilize the females.

Adults typically measure between 3–5 mm in length, and their bodies are often covered with a waxy secretion that helps them resist certain contact insecticides.

Coccus africanus primarily infests various fruit trees, citrus crops, and ornamental plants commonly grown in warm climates.

The pest targets young shoots, leaves, petioles, and occasionally fruits, extracting cell sap and causing significant stress to the host plant.

Damage is most severe in nurseries and young orchards, where heavy infestations can lead to premature leaf drop and stunted growth of young saplings.

Beyond direct feeding damage, the pest excretes honeydew, which serves as a substrate for the growth of sooty mold, a fungus that covers plant surfaces.

The combination of sap depletion and the clogging of leaf stomata by the fungal layer impairs photosynthesis, ultimately reducing crop yields and quality.

The life cycle of this pest is highly dependent on temperature and humidity, allowing for nearly continuous reproduction in greenhouses or subtropical environments.

The most active phase for crawler emergence occurs during the spring and summer months when ambient temperatures remain consistently above 18°C.

Females lay their eggs beneath their own bodies, which act as a protective shelter for the offspring until they are ready to emerge as crawlers.

Coccus africanus can produce several generations per year, with the developmental duration of each generation decreasing as temperatures rise toward the optimum range.

During the winter, the pest enters a period of reduced metabolism, typically overwintering as second-instar nymphs or young unmated females in sheltered bark crevices.

The first noticeable symptom of an infestation is the presence of characteristic rounded or oval brown bumps on leaves and stems, which can be easily dislodged by touch.

Leaf surfaces become sticky due to the excretion of honeydew, which frequently attracts ants that protect the scale insects from their natural predators.

Advanced infestations are marked by the presence of black sooty mold spots, which interfere with the respiration of the plant's tissues.

Affected plants show signs of slowed growth, yellowing, and deformation of leaves, and in severe cases, the dieback of individual branches may occur.

A large number of young individuals on the underside of leaves is a clear indicator that the pest has entered its active dispersal phase across the plant canopy.

Effective management requires regular monitoring of plantings, especially during the crawler emergence period when the insects are most susceptible to treatment.

Pruning and destroying heavily infested branches is a practical agronomic method to significantly reduce the overall pest population in the orchard.

Chemical control often involves the use of systemic insecticides that are absorbed by plant tissues and affect the pests during their feeding process.

• Applying horticultural mineral oils to suffocate the insects
• Utilizing biological control agents and natural enemies
• Implementing preventative sprays before the onset of the growing season
• Maintaining optimal growing conditions to boost plant immune systems

It is crucial to rotate insecticides with different modes of action to prevent the development of resistance in the pest population against specific active ingredients.