Walnut husk fly (Rhagoletis complete)
When is a pest not a pest? When it’s this week’s crawly! Meet the walnut husk fly (Rhagoletis complete).
Now we should clarify, the walnut husk fly isn’t a pest for most of us. True, their larvae can damage walnuts, but if you aren’t growing walnuts in your yard, don’t panic. You can just appreciate them for their undeniable beauty.
Moreover, there are just 27 recorded sightings of walnut husk flies in Oregon and 516 in the entire United States, so, seriously – don’t panic.
First fun fact: While the walnut husk fly is aptly named, in a pinch they will dine on a peach. However, they will only go for peaches if the peach tree is right next to the walnut tree and the walnut tree runs out of walnuts.
With so few sightings of walnut husks, you might think they are an introduced species, but nope! They hail from right here in the United States. They originated east of the Rockies but made their way west.
Fun fact: California grows 99% of all the walnuts for the US, while Oregon has only a small, but thriving group of walnut farmers. We can suss walnut husk flies probably came into Oregon from California.
With California’s massive walnut production, you might worry they are overrun with walnut husk flies, but again nope. There are only 67 recorded sightings of walnut husk flies in California.
As pests go, they just aren’t very pesty.
One reason for their small numbers is that walnut husk flies will stick to one, single tree generation after generation as long as that tree has walnuts. So even if one tree in a vast orchard attracts some walnut husk flies, they won’t “invade” the entire orchard.
This propensity for having a “home base” makes walnut husk flies relatively easy to control in situations where they might become “Capital P Pests.”
To be fair, we probably have more than the 27 recorded walnut husk flies in Oregon, but because the vast majority of our walnut trees are in abandoned orchards, no one really sees them, or worries about them.
Prior to 1962 there was quite an effort to grow English Walnuts in Oregon, especially Eastern Oregon, but a massive storm took out many of the trees that fateful year. Because walnuts grew much better in California, most Oregon farmers made the change to our state nut, the filbert and what walnut trees remained were abandoned.
In our area you’re more likely to stumble on an old black walnut tree, they have narrower leaves and are prized more for their wood than their walnuts.
Of course walnut husk flies enjoy black walnuts as much as they do English walnuts, so they happily set up house in those forgotten trailside trees.
Final fun fact: Walnut husk flies don’t necessarily harm the actual nut. Walnut nuts are inside walnut shells which are inside walnut husks. The flies lay their eggs inside the husk, outside the shell and that’s what their larvae eat.
The husks will soften and turn black, which may stain the walnut’s shell and make them less appealing to consumers, but the nuts inside are no less edible.
Sometimes the shell can be damaged and those nuts will drop from the trees, but that’s the minority of cases.
So even when walnut husk flies are Capital P Pests, they still aren’t that pesty.