As California almond harvest progresses, grade sheets and damage reports start putting numbers against the season’s navel orangeworm (NOW) pressure. When damage is higher than expected, it’s natural to ask what went wrong. But NOW damage is rarely the result of one factor or one tool.
Mating disruption is an important piece in the puzzle of managing NOW, but it is designed to work as only one component of your integrated pest management (IPM) program. The University of California recommends combining mating disruption with practices including winter sanitation, monitoring, well-timed insecticide applications, and timely harvest as part of your IPM program.
That makes the post-harvest damage report more than a scorecard. It’s an opportunity to review the entire program and identify where improvements can be made for next season.
Before drawing conclusions, take a closer look at what the damage report is telling you. NOW larvae typically leave extensive kernel feeding, webbing and frass. Other pests and disorders can also contribute to reject levels, so correctly identifying the source of damage matters. Representative harvest samples taken across individual blocks can provide additional context and help identify differences in pressure across the orchard. From there, compare damage against what happened in each block throughout the season.
Sanitation: How many mummy nuts remained after winter sanitation? Mummies provide overwintering and development sites for NOW, making their removal and destruction one of the essential foundations of an effective program.
Monitoring and spray timing: What did monitoring show throughout the season? Were applications aligned with pest activity, degree-days and crop phenology? At hull split, timing becomes particularly important as the new crop becomes susceptible to infestation.
Mating disruption: When evaluating mating disruption, consider deployment timing, coverage, dispenser density and whether there were untreated areas or neighboring sources of NOW pressure. Monitoring should also be interpreted carefully in mating-disrupted orchards because reduced male captures can be an expected effect of the program and should not be viewed in isolation.
Biological control: Beneficial insects can contribute to NOW suppression. However, the University of California notes that naturally occurring parasites should not be relied upon as a standalone control strategy, reinforcing the importance of combining compatible tactics into one holistic IPM strategy.
Harvest timing: How long was your crop left in the orchard? Harvesting as soon as good removal can be achieved can significantly reduce exposure to later NOW generations.
It’s also worth considering factors outside the block. Neighboring orchards and alternate hosts can contribute to immigrating NOW populations, while variety, shell seal, hull split progression and regional pest pressure can all influence final damage.
A high damage number deserves investigation, not a single-point explanation.
Review your harvest results alongside sanitation records, monitoring data, spray timings, mating disruption deployment and harvest dates. Look for patterns between blocks and across seasons by using the following checklist:
A post-harvest review isn't about finding one thing to blame. It's about understanding what happened throughout the season and using that information to strengthen next year's program. If you're reviewing your NOW damage and want another set of eyes on the data, reach out to our team. We can help look across monitoring, degree-days, mating disruption, sanitation, spray timing and harvest information to identify opportunities for the coming season.