Poplar scale

Systematic position. The poplar scale (lat. Diaspidiotus gigas) belongs to the order Hemiptera and the family Diaspididae. It is a specialized sap-sucking insect pest that spends most of its life cycle sheltered beneath a protective shield, which makes it highly resilient to environmental stressors.

Host plants. The primary hosts for this species are poplar trees, specifically Populus tremula, Populus alba, and Populus nigra. In urban landscapes and silviculture, the pest may also be found on willow species, causing significant damage to the bark and cambium layers of the branches.

Biology and life cycle. The species is univoltine, meaning it produces one generation per year. It overwinter in the first-instar nymph stage beneath shields on the bark. In spring, as sap flow begins, nymphs continue their development into mature adults. The female scale remains sedentary throughout its life, protected by a hard, waxy, and often colored covering.

Damage and economic impact. The damage is caused by the nymphs and females feeding on plant sap. Their feeding induces the formation of galls and swelling on the bark, leading to cracks, deformation, and necrotic tissue. Heavy infestations can lead to branch dieback, stunted tree growth, and a significant reduction in the aesthetic and ecological value of trees.

Control measures. Due to the protective shield, controlling Diaspidiotus gigas is challenging and requires precise timing:

• Application of dormant oil sprays in early spring before bud break to suffocate overwintering nymphs.
• Use of systemic insecticides applied during the crawler emergence period to target the most vulnerable developmental stage.
• Pruning and destroying heavily infested branches to reduce the overall population density.
• Maintaining tree vigor through proper fertilization and watering to improve natural resistance.