Japanese cottony scale

The Japanese cottony scale (Pulvinaria nipponica) is a member of the Coccidae family within the Hemiptera order. This scale insect is a significant pest known for its ability to infest woody plants, causing severe stress to the host through continuous sap extraction.

This pest is primarily found on stone fruits such as peaches, plums, apricots, and cherries. It may also affect various ornamental shrubs and trees. Due to its cryptic nature, it often goes unnoticed until the characteristic white, cotton-like ovisacs become visible on the stems and undersides of leaves.

The biological cycle consists of one generation per year, with the species overwintering as second-instar nymphs in bark crevices. As temperatures rise in spring, nymphs mature into adult females. These females produce large, white, wax-like egg sacs containing a high number of eggs, which hatch into crawlers during early summer.

Direct damage is caused by nymphs and females feeding on plant sap. Indirect damage is severe, as the insects excrete honeydew that coats the foliage and branches. This honeydew serves as a substrate for sooty mold, which inhibits photosynthesis, weakens the plant, and can lead to branch dieback or total yield failure in heavy infestations.

Effective management requires a combination of dormant oil applications to target overwintering nymphs and systemic insecticide treatments during the crawler emergence phase. Cultural practices, such as pruning heavily infested wood and maintaining tree vigor through proper fertilization and watering, are essential components of an integrated pest management strategy.