What's eating my english walnut 'howard'?

English Walnut 'Howard' is vulnerable to walnut aphid, walnut husk fly, navel orangeworm (especially in California, where 'Howard' is widely grown), and squirrels. Navel orangeworm is the dominant commercial pest concern for 'Howard', infesting nuts after hull split and causing significant kernel loss.

Larvae infest nuts at hull split, consuming kernels and introducing fungal contamination (Aspergillus mould); a major quality problem at harvest Early harvest as soon as 95% of hulls split; remove all mummy nuts from trees and ground after harvest; apply mating disruption dispensers in commercial plantings

Maggots blacken the husk from mid-summer; stains shells and reduces kernel quality Yellow sticky traps from July; spinosad canopy sprays timed to trap catch; kaolin clay barrier effective as a non-chemical option

Dense yellow colonies on leaflet undersides, causing premature leaf drop and reducing nut fill in heavy infestations Preserve parasitic wasps (Trioxys pallidus); avoid broad-spectrum insecticides that kill natural enemies; spot-treat with insecticidal soap if necessary

Pre-harvest theft of nuts from branches; gnaw bark on young 'Howard' scaffold limbs Baffled trunk guards; harvest early; netting for small trees