Almond scale

The almond scale (Pulvinaria amygdali) is a species of soft scale insect belonging to the family Coccidae. It is a common pest that impacts various stone fruit trees across many regions.

The adult females are characterized by their brown, convex bodies. During the reproductive phase, they produce a distinctive, white, cottony ovisac (egg sac) which makes them highly visible on the branches.

The nymphs, known as crawlers, are mobile during their early development stage. They are small and yellowish, allowing them to disperse effectively across the host plant before settling.

Reproduction is typically parthenogenetic, meaning the population can expand rapidly without the presence of males. This biological feature makes them highly resilient in favorable environments.

Monitoring for this pest is easiest during the spring when the white ovisacs appear on the bark, contrasting sharply with the brown branches of the trees.

The primary hosts for the almond scale include stone fruit crops such as almonds, peaches, apricots, plums, and cherries. It is considered a significant economic pest in commercial orchards.

These insects feed by sucking sap from the branches and leaves. This continuous removal of nutrients results in stunted growth, yellowing foliage, and a significant loss of plant vigor.

A secondary issue caused by this pest is the production of honeydew. This sticky substance covers leaves and branches, facilitating the growth of sooty mold, which blocks sunlight and interferes with photosynthesis.

Severe infestations can lead to limb dieback and the overall decline of the tree. If left untreated, the cumulative damage reduces fruit quality and overall yield potential for several years.

Additionally, the stress caused by the almond scale makes trees more susceptible to secondary infections, environmental stressors like frost, and attacks by other pests.

The almond scale typically completes one generation per year. The insect overwinters as second-instar nymphs, residing in bark crevices and under bud scales for protection.

As temperatures rise in the spring and sap begins to flow, the nymphs become active, move to fresh growth, and begin intensive feeding to reach maturity by late spring.

The egg-laying period occurs between late spring and early summer. During this time, the adult females form the prominent white ovisacs and remain stationary on the woody parts of the tree.

Crawlers emerge around mid-summer. They move toward the leaves, settling primarily along the undersides and veins to feed and continue their maturation process through the season.

By autumn, as temperatures drop, the maturing nymphs migrate from the leaves back to the branches or bark crevices to settle into their overwintering stage.

Effective management requires an integrated approach. Cultural practices such as pruning and removing heavily infested branches help to lower the initial pest population in the orchard.

Chemical control is most successful during the crawler stage, as the young insects have not yet developed their protective waxy shields, making them vulnerable to contact insecticides.

The use of systemic insecticides is highly recommended for reaching the pests hidden in crevices. Timely application based on monitoring and local pest reports is essential for high efficacy.

It is important to rotate insecticide classes to manage resistance. Always follow the manufacturer's label instructions regarding timing, concentration, and safety precautions.

Biological control, including the protection of natural enemies like ladybird beetles and parasitic wasps, can provide long-term suppression of the scale population in sustainable orchard management programs.