What's eating my manchurian walnut?

Manchurian walnut is notably cold-hardy and relatively pest-resistant, but walnut caterpillar and fall webworm can defoliate it in summer. The very thick, hard shell largely protects the nut from husk fly damage once husks close. Squirrels still raid the crop. In its native range it tolerates most pests well; North American plantings face typical Juglans guild insects.

Communal colonies strip foliage from entire branches; heavy infestations in successive years reduce growth and nut set. Monitor from late June; remove egg masses; apply Bt kurstaki at first-instar stage; rely on natural predators (tachinid flies, ground beetles) where possible.

Silken tents at branch tips house feeding caterpillars; cosmetic damage is the main concern on mature trees, but young trees can be significantly weakened. Prune out and destroy webs before they expand; apply spinosad to tent openings; no treatment needed on healthy mature trees with minor infestations.

Despite the thick shell, squirrels gnaw through hulls and shells to extract the kernel; buried caches mean many nuts never germinate or are harvested. Metal trunk banding; live trapping; harvest promptly when husks begin to crack or split naturally.