Mushroom Poisoning Alert: Boletus huronensis

By Greg Marley

A dry hot summer has been relieved by intermittent showers and thunderstorms bringing scant relief to a moderate drought across the state.  The mushroom mycelia responded to the heavy brief downpours to produce a bounty of mushrooms where nature was generous with rain.

As the mushrooms appeared, there was a surge in calls to the Northern New England Poison Center.  As usual, most of the calls involved children in the “grazer” stage of life; those toddlers and 3 year olds who sample the world by tasting everything of interest.  A few other calls involved adults who developed symptoms of poisoning after eating mushrooms they thought were edible.  All those who forage wild mushrooms for food need to have these mushrooms on their radar as common species that cause significant gastrointestinal distress!

Our usual culprits in Maine include the Lilac-Brown Bolete; Tylopilus (Sutorius) eximius and the Jack O’lantern Mushroom; Omphalotus illudens.  Both mushrooms have been responsible for sickenings in Northern New England this year already, as was a red-capped Leccinum which was eaten raw.

It is Boletus huronensis that I want all potential mushroom foragers to have on their radar!  

(Greg Marley photo)

Boletus huronensis has been the culprit in several cases of poisoning this year already and has also been involved in sickening foragers in each if the past several years.  Most of the time the person who foraged and cooked the mushrooms thought they were King Boletes (the Boletus edulis complex) and felt confident of having a great meal!

Boletus huronensis is a large handsome meaty bolete found growing in association with hemlock.  This mushroom has a warm yellow-brown to cinnamon-brown cap with an enrolled and often irregular margin and pale yellow flesh that stains slightly blue and a smooth pale yellow to cream stalk with faint traces of reddish blush.  The stem lacks the net-veining on the stalk that distinguishes its edible cousin, or may have it only at the very top.  The pore surface on B. huronensis remains pale yellow throughout its lifespan, unlike the edulis group that matures from white through yellow to green.  The pores also turn slowly blue when bruised.   Unlike the King Bolete group, this mushroom does not get attacked by the larvae of mushroom flies, perhaps the toxins serve that purpose for the mushroom (the same is true of T. eximius, the Lilac Brown Bolete) Though not commonly found, B. huronensis has been the cause of a number of severe gastrointestinal poisonings over recent years, leaving its victims miserable for many hours.  We have seen it or had reports of this mushroom from across Maine as well as New Hampshire and Vermont.

(Greg Marley photo)

The key differences between B. huronensis and the B. edulis group:

Flesh of all parts pale yellow, not whitish,

Stalk lacks distinctive net veining,

Flesh and pore surface bruise blue (may be slow and weak staining)

Causes severe and extended weakness, nausea, vomiting and diarrhea!

For an excellent full article on B. huronensis, see Bill Bakaitis’ treatment of the mushroom on the North American Mycological Association website https://www.namyco.org/boletus_huronensis.php

(Mary Yurlina photo.  B. huronensis is the yellow sliced mushroom on the right.  Notice the light blue staining, which then faded. Bitter bolete (Tylopilus felleus) is the other mushroom. Neither mushroom belongs on a kitchen cutting board!)