What's eating my english walnut 'serr'?

English Walnut 'Serr' (a UC Davis release, widely grown in California) is particularly susceptible to walnut husk fly, navel orangeworm, and walnut aphid. 'Serr' is an early-maturing cultivar, which can reduce husk fly damage if harvested promptly, but early hull split also exposes nuts to navel orangeworm.

Maggots in the husk cause black, rotting husks and reduce kernel quality; 'Serr' early maturity intersects directly with peak fly season Yellow sticky traps from July; apply spinosad spray when flies are first caught; harvest as soon as hulls split to limit exposure

Larvae enter through hull splits, consuming kernels and contaminating with Aspergillus mould; early hull split on 'Serr' creates a large window of vulnerability Harvest immediately at 95% hull split; eliminate mummy nuts from previous season; mating disruption dispensers in larger plantings

Yellow colonies under leaflets weaken the tree and cause early defoliation, reducing next season's productivity Conserve parasitic wasps; apply insecticidal soap or neem oil for heavy outbreaks; avoid carbaryl or other broad-spectrum sprays that disrupt natural enemies

Opportunistic raiding at hull split; 'Serr' nuts are taken as soon as they crack, especially in suburban settings Harvest immediately at hull split; baffled trunk guards; netting the canopy on smaller trees