Navel orangeworms attack far more than oranges and other citrus. They can seriously reduce your backyard apricot, almond, walnut, pomegranate, pistachio, date, fig, pear, apple, and stone fruit harvests.
You can protect your fruit and nut crops by learning more about this orchard pest. Navel orangeworm moths (Amyelois transitella) can fly in, deposit eggs, and be on their way in a matter of minutes, so monitoring regularly can go a long way toward protecting your foodscape.
Navel orangeworm description
Navel orangeworm eggs start out white. In 4 to 23 days, depending on temperature, the eggs will turn orange just before they hatch. The larvae are off-white or pink grubs with a dark head. If you look closely, you may be able to see a couple of crescent-shaped marks on the second segment behind the head. Adult moths are just under 1/2 an inch long, grayish brown, with irregular silver and black wing markings, and a snout-like appendage on the face.
Navel orangeworm lifecycle
Adult moths are generally present from March through October in California, and females begin laying eggs two nights after they emerge! Those eggs are laid on mummified fruits, newly forming fruits, and on freshly splitting almonds. The first instar burrows into a nut or fruit, where it, and future instars, will feed extensively. Next, the larva pupate in a webbed cocoon within the fruit or nut.
Damage caused by navel orangeworms
These orchard pests will devour an entire almond in the shell without ever being seen. If you examine an infested fruit or nut, you will see tiny entry holes and lots of frass and webbing. As they feed, navel orangeworms also provide entry points for fungal diseases and other pests.
You can protect your crops from navel orangeworm infestation by irrigating trees throughout the summer and by harvesting early and frequently. As always, remove mummies immediately and completely, every time they are seen. I have learned that there is a parasitic wasp, Goniozus legneri, that is supposed to be effective and commercially available. As soon as I can track down a source, I will provide an update.
Once infested, citrus fruits are pretty disgusting, so you will probably want to toss them in the trash. After harvesting almonds, pistachios, or walnuts, navel orangeworm eggs can be killed by freezing the nuts for 48 hours. After that, nuts can be stored at room temperature in airtight containers.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.