What's eating my english walnut 'hartley'?

English Walnut 'Hartley' is attacked by codling moth larvae, walnut husk fly, and walnut aphids. Squirrels and jays compete for the harvest, and deer browse young trees. In California (Hartley's main region), walnut husk fly is the most economically damaging pest, staining and rotting kernels.

Maggots tunnel through the green husk; husk blackens and adheres to the shell; kernel stained brown and shrunken Hang yellow sticky traps baited with ammonium carbonate to monitor adult emergence; apply spinosad bait spray (GF-120) at first trap catch; repeat every 7 days through harvest

Entry hole at stem or blossom end of nut; frass visible; kernel partially or wholly eaten Pheromone trap monitoring; apply spinosad or Bacillus thuringiensis at egg hatch; trunk banding to intercept larvae

Yellow stippling on leaflets underside; heavy honeydew and sooty mould; reduced photosynthesis and premature leaf drop Encourage parasitic wasp Trioxys pallidus (often self-establishes); spot-treat with insecticidal soap; avoid broad-spectrum insecticides

Whole nuts removed from the tree before full maturity; consistent pre-harvest losses Harvest as early as husks begin to split; trunk baffles to slow squirrel access; bird netting for small trees