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Belonochilus numenius

Sycamore seed bug

Description

Belonochilus numenius, commonly known as the sycamore seed bug, is a monophagous pest primarily associated with trees from the genus Platanus (e.g., Platanus acerifolia, P. occidentalis, P. orientalis). Native to North America, it was first detected in Europe in 2008 on the island of Corsica and has since spread across southern Europe. This insect feeds on sycamore seeds and occasionally on the sap from leaves and stems. The bugs overwinter beneath the bark of host trees, resuming activity in spring when they feed and reproduce on flowers, leaves and seeds.

High numbers of B. numenius can negatively affect the health and vitality of sycamores, particularly young or stressed trees, by reducing seed viability and causing localized damage to bark and leaves. Although the aesthetic damage, such as discoloration and scarring on seeds and foliage, is often more apparent than the impact on overall health, severe infestations can lead to reduced vigor, diminished growth, and increased susceptibility to secondary pests or pathogens.

Symptom

Affected seeds display small feeding punctures, discoloration, and premature drying. Bark near overwintering sites may exhibit tiny scars. Leaves show localized color changes and occasional deformation due to feeding activity.

Tree Species: Plane

Part of a plant- attacked: Leaf / Needle, Branch

Pest significance: Less harmful

Pest Category: Insects

Invasive Species: Yes

Present in EU: Yes