Navel Orangeworm in Walnuts

Common crops affected

Walnut

Why it matters

Navel orangeworm follows damage. Codling moth entry, sunburn and blight cracks all open a walnut for it, so the two pests compound rather than simply coexist, and the damaged kernel carries the same aflatoxin risk that concerns export buyers.

When to act

Time to the local flight rather than to a fixed date, and treat from hull split through harvest. Because codling moth is usually being managed in the same orchard on an overlapping schedule, the practical question is which passes can be combined and which have to stand alone. The pre-harvest stretch is the one conventional materials cannot cover, and it is where a zero pre-harvest interval changes what is possible.

What to look for

Crescent-shaped marks on the segment behind the head, which separate navel orangeworm larvae from codling moth.
Webbing and granular frass in the nut; codling moth leaves frass without the same webbing.
Entry at existing damage, including codling moth stings, sunburn and blight cracks.
Mummies retained in the tree over winter.

How to manage it

Sanitation over winter, as in almond and pistachio: mummies down and destroyed before bud swell.
Trap for both navel orangeworm and codling moth, and identify larvae before assuming which pest you have.
Treat from hull split through harvest, timed to the local flight.
Hold the window on a seven-day interval rather than stretching a contact residual.
Harvest promptly once removal is good; a delayed harvest extends exposure for both pests.

Recommended Vegalab program

Spider Mite Control · geraniol nanoemulsion, tolerance-exempt under 40 CFR 180.1251, applied foliar onto the nuts from hull split through harvest, alongside the orchard's codling moth program.

Role	Product	Use
Principal application	Spider Mite Control	1:500 · 51 fl oz/acre at 200 gallons of water per acre, foliar onto the nuts from hull split
Through the window	Spider Mite Control	Every 7 days through to harvest. Zero PHI and zero REI
Coverage aid, optional	Jumping Worm Control	1:800 · 32 fl oz/acre, in tank with the principal application

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Frequently asked questions

How do I tell navel orangeworm from codling moth in walnuts?

Look at the segment behind the head. Navel orangeworm larvae carry a pair of crescent-shaped marks there; codling moth larvae do not. Both are commonly present in the same walnut orchard, so identify before deciding the program.

Does navel orangeworm need existing damage to get in?

It strongly prefers it. Codling moth entries, sunburn and blight cracks all open a walnut, which is why the two pests compound and why managing codling moth also reduces navel orangeworm pressure.

Can the two programs share a pass?

Sometimes, and that is a decision for the orchard's own spray plan and the labels in front of you. What a zero pre-harvest interval adds is the ability to keep treating after the codling moth materials have run out of interval.