What's eating my filbert 'barcelona'?

Filbert 'Barcelona' is susceptible to hazel bud mite, hazelnut weevil, and in the US Pacific Northwest — where it is widely grown commercially — eastern filbert blight is the dominant disease threat rather than a pest per se. Aphids and filbert worm are secondary pest concerns. Squirrels cause heavy crop losses at harvest time.

Caterpillar burrows into the developing nut and feeds on the kernel; infested nuts drop early, and the larva exits through a small hole. Collect and destroy fallen nuts immediately; pheromone traps help monitor adult flight; apply a spinosad-based spray at first adult capture.

Grubs consume the nut interior, exit through a round hole, and pupate in soil; crop losses can exceed 50% in unmanaged trees. Remove and destroy fallen nuts; kaolin clay or labeled pyrethroid applied at nut gel stage; cultivate soil beneath trees to expose pupae to birds.

Swollen, globular buds that fail to open, reducing shoot extension and catkin production for the following year. Remove swollen buds in late winter; replace heavily infected trees; no effective acaricide is available to home growers.

Heavy pre-harvest theft of green nuts; can strip a tree completely before commercial maturity. Harvest early when possible; use trunk baffles; protect small trees with netting from late summer.