What's eating my chestnut 'colossal'?

Chestnut 'Colossal' (a Castanea hybrid widely grown in the US) is threatened by oriental chestnut gall wasp, chestnut weevils boring larvae into nuts, and grey squirrels taking the crop. Deer browse seedlings and fallen nuts. Chestnut blight remains a background risk on all Castanea.

Green to red galls on buds and leaf petioles in spring, reducing shoot extension and nut production; high populations weaken trees significantly. Biocontrol with Torymus sinensis parasitoid wasp (available in some US states). Prune out galled shoots. Select resistant rootstocks where available.

White larvae inside mature nuts consume the kernel; infested nuts drop early or are found hollow at harvest. Hot-water treat nuts at 49°C for 20–45 minutes after harvest to kill larvae. Collect and destroy all fallen nuts promptly. Permitted insecticides applied at burr split can reduce adult egg-laying.

Strip ripening burrs and remove nuts before harvest; persistent pressure can eliminate the entire crop. Harvest promptly as burrs begin to open. Trunk guards on young trees prevent climbing. Netting individual trees is practical for small plantings.

Browse young foliage and shoots on saplings; glean fallen nuts at harvest, competing with the grower. Tree shelters or 1.5 m wire guards protect young stems. Deer fencing around the plot is the most effective long-term measure.