Heartnuts and the Husk Maggot Fly

A veteran nut grower invited me over to pick up nuts from under his Heartnut tree.  We also picked a lot of Hazelnuts (but that’s another story).  I am a “newbie” to the nut and fruit growing world.  Every day I learn something new.  Last week it was Heartnuts and their pests.

Heartnuts are in the Walnut family (Juglans) so have a husk and a shell.  If the Husk Maggot Fly has the opportunity to lay her eggs in the exterior husk before it hardens it will be all mushy inside and this is what you will find.

Dennis Strahle, President of the Michigan Nut and Fruit Growers Association, said these are Husk Maggots.  They do not get into the nut but “turn the husk black and gooey. Removing the husk gets rid of the issue if you remove them timely enough so that the goo does not soak into the nut meats.” 

I husked the nuts and found maggots and mush in many of the husks.  It was pretty gross; the maggots were still alive and trying to crawl away from the light as I broke open each husk.  I discarded all the husks in a plastic pail, then transferred the husks to a plastic bag and into the trash.  The goo is really very dark and I was glad I had decided to wear my leather work gloves.  This is what my gloves and the nuts looked like after husking.

Notice that some of the nuts are much darker than others.  Those were the ones with the most maggots and gooiness.

“The primary damage from the husk fly is nutshell staining, which is a problem in commercial orchards where nuts are grown for in-shell sale; however, this can be tolerated in backyard situations. Feeding by the husk fly maggots also causes the damaged husks to stick to the shell, making them difficult to remove. An early season husk fly infestation (June to mid-August) can result in shriveled, moldy kernels.” (University of California, Statewide IPM Program, online)

The maggots overwinter in the ground (pupate) and emerge again in the spring.  For this reason, when you are husking nuts and find ANY worms or maggots place the husks in a plastic bag and discard them in your trash.  Do not compost the husks.

If you are a backyard orchardist you will probably never see the Walnut Husk Fly, especially if your trees are tall.  But you will see the damage.  If you can pull down a limb and look at your Heartnuts you may see a tiny black dot.  That means the Walnut Husk Fly has laid her eggs, usually near the stem.

This is a photo from the University of California IPM site.  Because Heartnuts are part of the Walnut family they are susceptible to the diseases and pests of walnuts.  The tiny black spot is where the eggs have been laid. 

I am using these nuts for my own purposes, so staining is not an issue.  Dennis Strahle says he sprayed his Walnuts “when the nuts were about the size of golf balls and looking green…”  That spraying took place around the last week in June and then he did another spraying about a week or two later.  He says his “nuts turned out  totally maggot-free and dropped very nicely and cleanly from the trees.” (e-mail communication).

I cracked out my Heartnuts and found beautiful kernels. They have a much milder taste than Black Walnuts, but not as sweet as English Walnuts.  The shell is also too hard for most nutcrackers but not as hard as the Black Walnut shell.

My nutcracker was not up to the job of cracking Heartnuts so I had to result to the hammer and cement block.

Since I first cracked the nuts above I’ve done a bit of research on how to crack Heartnuts. You have to hammer them on the sides, not the flat part, to have a better chance of getting that heart shaped shell that is advertised in nut tree catalogues.

  I’m proud to report that after cracking another 10 or so nuts I actually got a heart shaped shell.  Bear in mind that I am a “newbie” to nuts so this was an accomplishment to me!

I’m sure there are members of the MNFGA who can get heart shaped shells every time.  If you are a crafter I can see that growing Heartnuts can give you two harvests.

Number 1: tasty nuts. 

Number 2: that heart shaped shell to decorate for Christmas ornaments or whatever else you can imagine.

The world of edible nuts is an interesting one full of adventures.  There are so many different species of nuts and they have been a food source for so many peoples all over the world for eons.  Take some time to find out about the nuts in your neck of the woods. 

Better yet; join the MNFGA and find mentors to help you on your quest for tasty nuts (and fruits).


2 responses to “Heartnuts and the Husk Maggot Fly

  1. He doesn’t use any spray. He’s only growing for personal use and the maggot cause discoloration. Every now and then he loses a nut but he considers that sharing. Sorry I can’t be more help.

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