Walnut lace bug

The walnut lace bug (Corythucha juglandis) is a tiny insect belonging to the Tingidae family within the order Hemiptera. This pest is named for the intricate, lace-like pattern on its wings and thorax, which acts as camouflage against the leaf surface. They are typically found on the undersides of leaves, making them difficult to detect early on.

These insects primarily infest walnut trees (Juglans species), such as black walnuts and English walnuts. While they show a strong preference for walnut hosts, they have also been documented on other deciduous trees like basswood and occasionally willow. They feed by piercing the plant tissue and extracting cell contents with their sucking mouthparts.

The lifecycle begins with adults overwintering in protected sites, such as bark crevices or leaf litter. As temperatures rise in spring, the adults emerge, feed, and mate. Eggs are laid in clusters on the undersides of leaves. The nymphs pass through several instars before maturing, often resulting in two generations per growing season in warmer climates.

Feeding damage manifests as chlorotic stippling on the upper surface of the leaves, where the cells have been drained of chlorophyll. As the population increases, these spots coalesce, leading to premature leaf browning and leaf drop. The presence of dark, varnish-like excrement spots on the underside of the leaves is a definitive sign of an active infestation.

Effective management focuses on minimizing overwintering success and chemical intervention when necessary.

• Sanitation by removing fallen leaves in autumn to reduce hibernating sites.
• Maintaining healthy tree vigor through proper irrigation and fertilization.
• Applying contact or systemic insecticides during the nymphal stage when they are most vulnerable.
• Monitoring the canopy closely during mid-summer.