What's eating my pistachio?

Pistachio trees are attacked by navel orangeworm inside the nut, leaffooted bugs that feed on developing kernels causing blank or shriveled nuts, and aphids on foliage. Squirrels and birds take ripening clusters. Navel orangeworm is the most economically damaging pest in California, the dominant US growing region.

Larvae enter split pistachio shells and consume the kernel, leaving webbing and frass; contaminated nuts also carry aflatoxin risk in storage Early harvest at first split; complete winter sanitation including mummy clusters; pheromone traps to time harvest and sprays; spinosad at nut split if trap counts are high

Piercing-sucking feeding on immature nuts causes blank nuts (no kernel development), shriveled kernels, or dark spots; feeding site becomes a fungal entry point Vacuum or knock bugs into soapy water early in season; kaolin clay deters feeding; pyrethrin spray around orchard borders; remove weedy border vegetation that harbors overwintering adults

Similar piercing injury to leaffooted bugs — blank or gummy nuts with feeding scars Monitor borders early; pyrethrin or spinosad at threshold; weed management at orchard perimeter reduces harborage

Honeydew and sooty mold on leaves and nut surfaces; heavy infestations reduce photosynthesis and tree vigor on young trees Encourage parasitic wasps and lacewings; insecticidal soap or neem oil; avoid nitrogen over-fertilization