Written By Adam McCrae
Please note: foraging for wild mushrooms is not a game. Never eat any wild mushroom that has not been identified as edible with 100% confidence by someone qualified to do so. Always cook wild mushrooms before eating, and if the species is new to you: cook thoroughly and only try a couple bites the first time, to make sure your body doesn't have an intolerance.
Have you ever gotten home from a foraging trip and realized that, upon closer inspection: your mushrooms are a little too... crawly, for your liking? Or, even worse, gone to your hard-earned mushroom stash in your fridge a few days after picking them only to find a writhing mass of larvae where your delicious mushrooms used to be? You are not alone.
My name is Adam McCrae, and I have been foraging and studying mushrooms for the past 20 years or so. In this short blog, I'll be imparting some of the best tips and tricks I've learned over the years to remove bugs and worms/larvae from your foraged mushroom bounty. (No, those little white bugs with black heads aren't actually worms, but they sure look like it!)
Before we dive into how to get rid of them, let's take a quick look at a few of the more common inhabitants of wild mushrooms: Springtails, Fungus Gnat Larvae, and Slugs/Snails.
Close-up of springtails, courtesy magickcanoe.com
Springtails can often be found in large swarms on the exterior of mushrooms like Lactarius and Russula, but they seem to be opportunistic feeders and can be found on just about any mushroom to some degree. These fascinating little creatures are actually pretty adorable up close, and also basically harmless. Eating a few won't harm you, which is good because they can be quite prolific and are very small (0.5-3mm). A few quick facts about springtails:
- They have no larvae cycle, the babies are just smaller versions of the adults.
- They get their name from their defensive mechanism: the ability to jump up to 10cm, which is really impressive given their minute size.
- In natural forested areas, they can be found in numbers of up to 50,000 per square foot!
Hundreds of dead springtails, a somewhat common occurrence when mushrooms catch and hold rainwater, courtesy www.foxeslair.org
Fungus Gnats / Fungus Gnat Larvae:
Mature fungus gnats mating on some Oyster Mushrooms (Pluerotus sp.). Photo courtesy Bill Sheehan
If you see these mosquito-esque little guys flying around your mushrooms, chances are *extremely* high that they've already done their business and laid eggs inside the mushroom you intend to eat. They also have a tendency to go and die on the outside/around the base, and even curled up inside the lobes of Morel mushrooms, which is... annoying. 😅
Their adult, flying stage is annoying enough, but what their larvae can do to a day's harvest in a very short period of time is both impressive and terrifying. Properly stored, pristine-looking mushrooms can turn into a wriggling mass of little white worms within a matter of days, even if you didn't see a single larvae to begin with!
Some quick fungus gnat facts:
- While they resemble mosquitos, they cannot bite and are harmless to humans... but they can be incredibly annoying, flying into your eyes, nose and mouth and often in large swarms.
- Their larvae are also harmless, and edible, which is good because even with the best of methods, you're not going to remove every single one.
- The term "fungus gnat" applies to dozens of species over several families of animal, and I'm not going to even begin to differentiate them here. 😅
Close up of a fungus gnat larvae, note the white body and black head. Photo courtesy Tom Murray
Hungry little guy. 🐌 Photo by Lynn Harrison
These captivating little creatures often leave their mark on mushrooms, taking large chunks out of the cap, stem or both! If they haven't slimed it up too bad, you can just remove them (if they're still there) and trim around the bitten area. They're generally not one to hide, but tiny slugs *will* sometimes live inside the lobes of certain morel species.
- Slug/Snail mucus is generally considered harmless, but there are exceptions and that's one reason one should always cook wild mushrooms before eating them.
- Snail eggs are often confused for certain species of Slime Molds.
- This Snail and Chestnut Mushroom Sticker made with my wife's artwork is freaking fantastic.
Straightforward advertisement for my wife's awesome mushroom art. It had to go somewhere, I'm keeping it short and sweet. Mushroom cleaning tips are just below. 🥰
Alright, let's get to the good stuff:
How to get bugs/worms out of Mushrooms
Method #1: Trim/Rinse
This is a simple, quick tactic that can be used for most mushrooms. Trim any obviously bitten or discolored areas of the mushroom, and also *slice across the base of the stem to check for bug holes*. These small, circular holes in the cross section of a mushroom are a sure sign that fungus gnat larvae or similar has hatched and is already crawling around inside your potential dinner. In most cases, eggs are laid in the base of the stipe and the larvae travel upward, so it is often possible to just keep trimming up the stem until you don't see any more holes on the bottom. If you see a large number of these holes that travel a significant way up the stem but still want to preserve your mushrooms, don't rinse yet, but go straight to Method #2! If your trimming doesn't reveal any holes that imply bug damage, go ahead and lightly rinse the mushroom, then leave it on a towel to dry until you're ready to use it. For more specific tips and tricks on How To Clean Foraged Mushrooms, just check out my other blog. 🙂
Method #2: Sealed Plastic Bags:
I know, I know, some of you are thinking "you can't put mushrooms in plastic, that will ruin them!". Well, I'm here to respectfully tell you: you can! Not only *can* you, I am heartily suggesting that you do so, if you see signs that your mushrooms have fungus gnat larvae inside! I'm not saying that you should be doing long term storage in plastic, but rather a short stint to draw out and kill any bugs that may have taken up residence. I've used this method to great effect with morels and boletes, but I don't see why it wouldn't work with nearly any mushroom hearty enough to withstand a tiny bit of suction pressure. Here's how it works:
- Place your mushrooms inside a plastic bag that will hold a good seal, such as Ziploc.
- Close all but one small corner of the bag, then use your mouth (or any other method) to suck as much air out of the bag as you can, then seal it shut.
- Place the bag inside your refrigerator for 8-10 hours.
- The larvae inside the mushrooms will crawl out and cling to the sides of the plastic bag in search of air.
- After 8-10 hours, just remove the plastic bag, dump out the mushrooms, and brush off any larvae still clinging to them.
- You can then store them as usual, ideally in paper bag or cardboard box with loose lid
- This method also works to kill *potential* larvae, as the eggs no longer seem to hatch.
- No, this won't remove every single larvae, but it does remove 99% or more. If you spot some during the rest of the cooking process, just pick them out if you want.
13 pounds of morels ready for 10 hours in the fridge.
Method #3: Water/Saltwater Soak
Five pounds of Morel Mushrooms getting a short saltwater bath.
Now, this one also gets frowned upon, but just hear me out. 😅 For certain mushrooms, like Morels and Oysters, a *short* soak in water/saltwater is not going to harm their texture and will quickly draw out/kill bugs and larvae that may be inside. I would not suggest more than a couple tablespoons of salt per few cups of water, as the mushrooms may become too salty. I would also not suggest leaving them to soak for more than 5-10 minutes, as the texture will slowly start to degrade. Freshly picked, hearty morels will often survive the days of soaking that some people prefer, but they are not the same mushroom after 3 days in saltwater. Please don't do that to them. 😊 If you do soak or rinse your mushrooms, leave them out (gill side down, for oysters) to dry for a bit before use or storage. I would never suggest saltwater soaking mushrooms with pores like Boletes/Porcini, or fragile mushrooms such as Shaggy Manes. Also note that this method is likely to drown a lot of the bugs before they have a chance to exit, so while they might not be alive, you may still see them during cooking.
Method #4: Don't
Yup. Just eat them. The springtails and larvae are harmless. They've probably spent their entire life eating nothing but mushroom you're about to eat, so are mostly made of it anyway. 😅 Some people even refer to fungus gnat larvae as "tiny little bacons", since they crisp up when you sear off your mushrooms. I personally have a limited larvae-to-mushroom ratio, but that's mostly just western culture that I have a hard time shaking off. If you're into eating bugs, go for it! Just be aware that bug damage and well-aged mushrooms often go hand in hand, so be sure that the mushroom you're eating is still in its prime besides the bug damage.
Method #5: Dehydrating
Several pounds of Morel Mushrooms about to go into a 10-rack dehydrator.
This method, like the rest, is not going to guarantee that every single bug is gone, but it certainly gets the vast majority. Slicing your mushrooms thin is going to mean you're killing a lot of the larvae you intend to remove, but hollow mushrooms like Morels can just be cut in half and dehydrated for later use. When the heat of a dehydrator is applied, the bugs come crawling out of the mushroom searching for better conditions, fall to the bottom of the dehydrator and die. Of course, if your dehydrator has multiple racks, they fall onto the mushrooms below... and some won't make it all the way out/off the mushrooms at all. Most of these can just be brushed off after they come out, but there will almost always be some "leftovers", if you will. 🙂
Bonus tip, since #4 wasn't really a method:
If you have access to CO2 and a way to pump it into plastic bags, I have seen multiple anecdotal reports that pumping plastic bags with CO2 and then sealing them has the same effect, if not faster, than sucking the air out.
Do you have any other tips to getting bugs out of your mushrooms? I'd love to hear them, if you want to drop a comment below! Please make sure to give us a follow on Instagram and Facebook, and join our Email list below.