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Taming The Fungus

This post was written by a student (now a recent grad) who developed his talent with mushrooms by taking classes and participating in just about every mushroomy possibility Cornell has to offer.

To many of us the fungus is a strange and elusive organism, mysteriously appearing from its substrate, and then suddenly disappearing back into the mass from which it arose. The diversity of fungal shapes and sizes combined with the wide array of substrates from which they fruit, has often created the illusion that fungi come and go as they please. However, with a little knowledge about the biology and ecology of these organisms, one can often capture and cultivate a fungus found growing in the wild.

The first step to growing your fungus is obtaining a specimen. You can culture molds if you like, but I’m betting that most of you are more interested in growing mushrooms. Find a fresh mushroom that hasn’t begun to show any signs of decay–younger mushrooms are preferred, as the fungus is still actively growing. Typically mushrooms must be cultured within 24 to 48 hours of being picked, and until you can get to them it’s a good idea to store them in your refrigerator. I have chosen to culture this prime specimen of Hypholoma sublateritium, which I found growing in a nearby forest (see our previous story on this “edible?” fungus).

Now you will want some tools. These include a bottle of alcohol (ethanol or isopropanol), some matches, a scalpel, a pair of tweezers or forceps (finer is better), and a few Petri dishes of potato dextrose agar (PDA). PDA is kind of like Jell-O™ made from boiled potato water. Instead of gelatin (which most fungi can digest), indigestible agar creates the gelatinous nature of this substance, and the potato water and sugar serve to feed the fungus as it grows in culture (you can make PDA yourself^1,2 with some potatoes and sugar, agar you buy from an Asian grocer, some mason jars, and a pressure cooker as a sterilizer). While you’re gathering tools, don’t forget a notebook. It is also a good idea to record some notes about your fungus, include where and when you found it, what it was growing on, and any other characteristics that seem unique or important. You’ll be amazed at how quickly you forget this type of information if you don’t record it, and how useful it can be in identifying your fungus.

One of the greatest difficulties of culturing any fungus is dealing with contaminants. Contaminants are weeds–other organisms that want to get in your Petri dishes so they can eat your media first. Fungal spores and bacteria spores are so small that a cubic meter of air may contain thousands of them. That’s why it is very important to work in a clean environment with still air, and to sterilize your tools before use. Some people make a special “glove box” designed to provide a pocket of clean air, but this isn’t a necessity. Although your Petri dishes of PDA must be sterilized in a pressure cooker or autoclave, many of your other tools can quickly be sterilized by dipping them in alcohol and then flaming it off with a match or lighter.

Once you have gathered all of your supplies and are ready to work, the first thing you must do is sterilize your tool of choice: at left I am flaming the remaining alcohol from my tweezers. Immediately after this, use your fingers to tear the mushroom in half, exposing its internal tissue. Be sure not to cut the mushroom open with a blade, as this will drag contaminants from the outer surface of the mushroom to the more sterile tissue within it.

Now use the tweezers to pluck a teeny tiny piece of tissue from the newly revealed inside of the stem or cap, and then quickly place it in the center of your Petri dish. Seal the dish with tape or parafilm, and voila! you have captured your fungus in culture. The mycelium that will grow from your tiny piece is a genetically identical to the parent mushroom. You may have inadvertently captured a few other things, too, so I like to set up three or four dishes–this way I am more likely to get a culture without any contaminants.

Within several days to a week you should begin to see the first signs of growth, as mycelium grows outward from the piece of tissue in the dish. You’ll want to transfer a teeny tiny chunk taken from the edge of that colony to a new Petri dish, to make sure it’s contaminant-free. The appearance of this mycelium varies greatly depending on the species of fungus that you are culturing. This can make it difficult to spot contaminants if it is your first time culturing that species. Any colony that arises elsewhere on the plate is probably a contaminant that arose from a single spore deposited in air. Slimy, mucusy colonies might be yeasts or bacteria. Anything blue or green is most unwelcome.

Capturing your fungus in culture is the first, essential step in mushroom cultivation. I hope we’ll talk more about this another time, but for now I’ll refer you to an expert: If you are interested in learning more about mushroom tissue culture and the contaminants you will encounter, The Mushroom Cultivator, by Paul Stamets, is a great book.

Lactarius helvus, the maple syrup milky cap

This post was written by Ariana Verrilli, a curious student in PLPA 3190 in Fall 2008.

Lactarius helvus is a milky cap of the family Russulaceae, and occurs widely throughout North America and also Europe. It generally grows in boggy, mossy areas and is probably mycorrhizal with coniferous trees. It has some easily identifiable characteristics. This milky cap releases a watery and colorless latex that does not stain the flesh of the mushroom. The whole mushroom has a distinct scent reminiscent of curry or maple syrup. Although this odor is sometimes weak in young specimens it becomes more pungent upon drying. Is it toxic? Some authors report this mushroom in North America to be mildly poisonous while others claim that it is edible (but see below!).

In 1979 Hesler and Smith began calling this mushroom Lactarius aquifluus Peck, instead of using the older name Lactarius helvus. Michael Kuo has provided a fine explication of this name confusion. Let’s call it L. helvus for now, but should our North American species turn out to be different from its European cousin, L. aquifluus will be back in style.

The distinct smell of Lactarius helvus comes from a cyclic ester called sotolon (or 3-hydroxy-4,5-dimethyl-2(5H)-furanone, if you must know). Sotolon is a powerfully aromatic compound, and is a highly recognizable characteristic of Lactarius helvus. At high concentrations sotolon smells strongly of curry or fenugreek, and at lower concentrations it smells like maple syrup or caramel. As L. helvus mushrooms are dried their odor tends toward fenugreek. A number of foods, including lovage, molasses, rum, and roast tobacco also contain sotolon. It is a component of some wines that develops with aging–it is especially pronounced in French vins jaunes, sherries, Port wines, and botryotized white wines like Sauternes. When oenophiles (wine geeks) smell sotolon, it suggests to them that the wine is well-aged.

In Europe, Lactarius helvus is considered mildly toxic. If large quantities are eaten raw, symptoms can occur. On average it takes 15 minutes to 1 hour for signs of poisoning to appear: These include vomiting, copious diarrhea, and sweating. In Leipzig, Germany in 1949 an estimated 418 people were poisoned by Lactarius helvus. This group of people experienced nausea, vomiting, abdominal pains, salivation, vertigo, diarrhea, disability, and a cold feeling. All survived. Although not much is known about the toxin in Lactarius helvus, it is definitely not sotolon. Some speculate that the toxic component is a sesquiterpene. It appears to become inactive upon boiling (or perhaps it is leached out). In northern Europe this mushroom is sometimes dried and used in small quantities as a spice (a practice which wise Dr. Benjamin says is “ill-advised”).

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Editor’s Note: Despite its drab colors, Lactarius helvus is one of the milky caps that ordinary muggles like me can identify–because of its odor. There are very many Lactarius species–Hesler and Smith treated over 200 in North America. A few other milky caps are distinctive, such as the lovely Lactarius indigo (yep, it’s blue), but often Lactarius species are tough to identify. That’s why we can all be excited about a forthcoming book, Milk Mushrooms of North America: A Field Identification Guide to the Genus Lactarius by A.E. Bessette, D.B. Harris, and A.R. Bessette (Syracuse Univ. Press 2009). I haven’t seen it yet–it’s due out in Fall 2009. I can hardly wait!

How to eat a bolete

A hungry student who took my Mushrooms of Field and Forest class in 2007 wrote this mouth-watering post.

Although I grew up equidistant from a large woodland and the local grocery store, I never would have thought that they contained some of the same products. The woods had carefully marked trails and swimming holes, the supermarket carefully marked bins of produce and even mushrooms. But the second week of my Field Mycology class, I collected my first bolete, something I’d thought I could only buy dried at my supermarket. The process of finding and eating boletes is much different in the wild than it is in civilization, so I’ll describe the path from the forest to the mouth for a delicious bolete.

The most coveted boletes belong to the Boletus edulis group (right), and are rarely found fresh in stores; generally only dried boletes appear. Unlike white button mushrooms, boletes are not saprobes that can grow on compost; they are mycorrhizal, forming relationships with trees. Due to the expense and complications of trying to cultivate a mushroom with a specific tree, there has been little success, so boletes are always collected from the wild, making them uncommon and expensive in supermarkets. However, the good news for collectors is that because they are mycorrhizal (symbiotic with certain trees), they will recur in the same places each year.

Because boletes are mostly water, dried boletes barely resemble fresh ones. While the dried boletes appear very similar to other dried mushrooms, fresh boletes are thick and fleshy, and distinct from other mushrooms because they have a thick sponge of tubes (often yellow) on the underside of the cap, instead of gills. However, although it is generally easy to recognize a mushroom as a bolete, identifying your bolete to species can be more difficult. This is an important step, because many boletes are either poisonous, or simply not pleasant to eat. (In France, pharmacists will check your mushrooms for you–all are trained in mycology).

My first bolete was Boletus parasiticus (at left). This mushroom is easily identified because it grows out of an earthball (Scleroderma sp.). Although it is not poisonous, one should be careful before eating it because the earthball is poisonous, and has powdery, easily distributed spores. Choice mushrooms from the genus Boletus include B. appendiculatus, B. regius, B. badius, B. erythropus, B. mirabilis, and B. zelleri. Other good edibles are found in other bolete genera, including Suillus, Leccinum, and others. Some are not so good, including, for example, the bitter boletes of the genus Tylopilus, (below) which will give you a belly ache, Boletus satanus and allies (anything named after the devil is likely to be poisonous), and a fatally poisonous Australian species of Rubinoboletus. [Editor’s note: don’t try to identify your boletes based on our story–consult a more comprehensive source like Michael Kuo’s MushroomExpert.com, or Bessette et al.’s big bolete book²]

Once the mushrooms have been properly identified, it’s time to begin preparing them. Boletes rot quickly; any wet and mushy undersides or insect-filled stems should be discarded. The hard or fibrous stem of an older bolete should also be removed. The best boletes are small and firm. The choicest specimens can be served raw, thinly sliced with lemon juice and oil. However, there are a variety of cooking methods to best showcase the meaty flavor of boletes.

The classic French method includes three stages. First, the mushrooms are partially dried in the oven to remove some of the water. Then, they are stored in the exuded liquid, so that the flavor is not leached away. Finally, they are sauteed, to brown and cook them.

And though I may have seemed to disparage dried boletes as very unlike fresh boletes, dried boletes are not inferior. In fact, the distinct change that takes place during drying is seen by many as an improvement. The enzyme action and browning reactions that take place during drying give the dried bolete a powerful taste that can be used to infuse many foods with its umami flavor. And they last as long as a year.

Dried boletes should first be soaked for 30 minutes, and as with fresh boletes, the liquid is highly flavorful. When the rehydrated boletes are sauteed, they will have more flavor if they are cooked with the liquid. Although the texture of these are lacking, they are excellent for adding flavor to soups, or as flavoring in salads or meats. One interesting suggestion is to add a small amount of dried boletes to ordinary cultivated white mushrooms to give the dish a much richer and deeper flavor.

No matter how you eat ’em, boletes will give your food a meaty and earthy flavor reminiscent of the forest they came from.

Small friends of fungi

Dr. Robert Mesibov contributed this post. He’s a taxonomist from down under who studies seriously fungophilic animals: millipedes.

If you studied the traditional sort of biology, you’re probably carrying around an unfortunate prejudice.

You see terrestrial habitats as a simplified nutrients-and-energy pyramid. At the bottom are green plants, feeding on sunlight, carbon dioxide and soil water and minerals. Next layer up on the pyramid is the herbivore mob: leaf and stem eaters, sapsuckers, root nibblers, seed and fruit gobblers. Above these green feeders are a couple of layers of predators. And that about sums up the world, right?

Wrong. That’s only part of the world, and a small, very specialised part of it, too. To begin with, most animals can’t eat green food. Herbivores are dietary specialists among the insects, mollusks, birds and mammals. Your average green leaf or stem doesn’t show much herbivore damage, and for good reason. It’s mainly water boxed in by cellulose and other structural carbohydrates, which are impossible or extremely hard for animals to digest. Other nutrients are present, but at low concentrations. You need to eat a great mass of indigestible green stuff to get a decent return of elements like nitrogen, phosphorus, potassium and calcium. As for animals eating wood, which makes up most of the biomass in a forest – well, there are termites, and…um…termites…

The truth is that in the real world outside the biology classroom, only a tiny proportion of terrestrial primary production goes through the stomachs of the few evolutionary lineages brave enough to tackle what green plants produce. In any terrestrial habitat, the great bulk of primary production just does *not* get eaten. It sits, instead, at the bottom of a very different food pyramid. I call it the Dead Plants Society (DPS), as opposed to the Green Feeders Guild (GFG).

In the absence of fire, all that uneaten primary production is first attacked by fungi and bacteria. By ‘attacked’ I mean ‘converted from low-nutrient indigestibles to concentrated yummies’, i.e. fungal and bacterial bodies. Stacked on top of this microbial layer in the pyramid are microbivorous layers of nematodes, mites, springtails, earthworms, millipedes and other soil animals. On top of those are predators – but picture ‘centipede’, not ‘eagle’.

The GFG and DPS animal communities differ in many ways. To begin with, in any given habitat the GFG has very high species diversity (think of plant-eating insects) but low higher-taxon diversity, while the DPS has great higher-taxon diversity (lots of strange sorts of animals), but low species diversity. Next, GFG herbivores tend to specialise on particular plants, while DPS microbivores will eat anything that’s rotting nicely. There are also a lot of winged GFG members (‘gotta find that particular plant I like…’), whereas almost no DPS members have wings, at least in their younger, feeding stages. There’s an architectural difference, too. The GFG extends well up in the air, to ca. 100 m in some tall forests, while the DPS is largely confined to the ground.

Then there’s the matter of heritage. The earliest DPS fossils are of mites, springtails and millipedes, and they’re more than 400 million years old, from a time when terrestrial vegetation was mainly mossy and ground-hugging. The first solid evidence for green feeding (early insects with spores in their guts) appears much later in the fossil record, from coal swamp times. The DPS is vastly older than the GFG, and when you handle richly organic soil you’re holding animal communities which are spectacularly ancient and robust. You can almost imagine a springtail thinking: ‘Seen the dinosaurs come and go, mammals are nearly done. Wonder what great lumbering dopes we’ll see in the next 100 million years? Yum, love these hyphae with yeast sprinkles!’

Paleomycology: Discovering the fungal contemporaries of dinosaurs

This post was written by Christine Layton, a talented PhD student in Plant Pathology and Plant-Microbe Biology here at Cornell.

Almost everyone has been to a museum like The Smithsonian and seen firsthand the relics of our planet’s evolutionary past. Most of the fossils we find belonged to creatures that have long been extinct, but many of those bear a striking resemblance to organisms we share the earth with today. As with the fossilized remains of plants and animals with which most of us are familiar, fungi that existed millions of years ago have also been preserved and can be studied by paleomycologists — that special breed of mycologist who studies fungi in the fossil record.

Some of the most fantastical discoveries of ancient fungi have been in amber. Amber comes from certain species of trees whose sap was able to resist decay and weathering, and thus hardened and became fossilized over millions of years. Anything (including fungi!) that became trapped within the sap before it hardened became completely preserved– just like a time capsule. Amber deposits exist worldwide, but two of the most important are on the coast of the Baltic Sea and in the Dominican Republic. Both of these deposits differ greatly in age: Baltic amber dates around 35-55 million years old during the Eocene, or at about the time that the first modern mammals appeared, whereas Dominican amber is from the Miocene (about 15-20 million years old), making it about half the age of Baltic amber.¹ This important age difference gives us snapshots of two completely separate periods in our planet’s history, a real boon for evolutionary biologists.

Many insightful discoveries have been made about what fungi were like millions of years ago. It seems that while many of the fungi that existed back then clearly differ from the ones that exist today, the fungi of today bear a striking physical resemblance to their ancestors. And from what we can tell, it seems that ancient fungi walk the same walk and talk the same talk as their modern counterparts, too. Many fungi are parasites — of plants, of insects, and even of each other. So, it is not surprising that we should find them doing the same things in the fossil record.

One of the more well-preserved specimens of a fungus in amber comes from a piece of Baltic amber that contains a springtail (an arthropod closely related to insects) which is likely being parasitized by Aspergillus collembolorum, a previously undescribed species. The sporulating fungus is so well-preserved that the individual conidiophores (spore-bearing structures), complete with conidia (spores), can be clearly seen erupting from all over the body of the springtail. Using these physiological characters, it was placed in the modern genus Aspergillus, whose species are primarily saprophytic. However, some species are known to be facultative parasites of insects. Because A. collembolorum is the only fungus on the springtail, as well as the fact that the springtail was not decomposing when it was trapped, it is likely that the Aspergillus was acting as a parasite and not a saprophyte.² Investigating fungi trapped in amber is almost like figuring out what happened to a victim in CSI, since you have to follow the clues from what happened at the time of death to really figure what the fungus was doing, its identity, and perhaps even how it lived.

There have been some other remarkable finds of parasitic fungi of insects in amber. In Dominican amber, a mosquito was found with several types of parasitic fungi growing on its outside cuticle. What is interesting is that the fungi resemble modern day fungi in class Trichomycetes, which are common gut-inhabiting zygomycetes of insects, but they differ from Trichomycetes in that the fungi are on the outside of the insect rather than the inside. If the fungi are indeed Trichomycetes, this could be important for figuring out when the ability to live in insects’ guts was acquired in the lineage.³ Another interesting find, this time in Baltic amber, is of a parasitic fungus consisting of four club-shaped fruiting structures erupting out of the thorax of a stalk eyed fly. What’s really neat is that the fungus physiologically closely resembles a modern day Laboulbeniales, which are obligate parasites of insects and are often very host-specific. Since the fungus was found on a fly, it was able to be placed in the modern genus Stigmatomyces, which is specific to flies. This fossil, which is the oldest record of an insect-parasitic fungus, shows that these host-specific insect pathogenic fungi have existed for tens of millions of years.^4,5

Now probably one of the coolest fungal finds in amber has to be from a piece of Burmese amber dating to about 100 million years old, or around the time when the dinosaurs were in their heyday. Within this piece of amber is a fungus parasitizing a fungus that is parasitizing yet another fungus. You heard me right: three fungi eating and being eaten by one another. I should also probably mention that the piece of amber in which this was all found is itself smaller than a grain of rice! In the amber is the cap of the basidiomycete Palaeoagaracites antiquus, whose gills are covered by the hyphae of the mycoparasite Mycetophagites atrebora. And amazingly, inside of the hyphae of that mycoparasite are the hyphae of the hypermycoparasite Entropezites patricii. All three fungi were described as new genera and species from this single sample. The specimen is so well-preserved that portions of P. antiquus‘s gills appear to be liquefying from toxins released by M. atrebora. Nowadays such complex and sophisticated levels of parasitism are known amongst fungi, but the fact that they were so well-established some 100 million years ago is simply astonishing.⁶

But really, why do we even care about all of this? Knowing what kinds of fungi were out there and getting a glimpse of what they were doing millions of years ago is vital to the understanding of the evolutionary histories of the species we have around today. While we may have a good understanding of the relationships between many plants and animals, we know relatively little about the true evolutionary history and relationships of most fungi. A recent phylogenetic study using highly conserved DNA has shown that the morphological characters–primarily those of fruiting bodies–that we use to identify fungi are far from perfect at revealing the true evolutionary relationships between groups. It’s become quite clear that some traits once considered to be homologous, like the presence of gills or an enclosed sac-like fruiting body, have evolved multiple times in different phylogenetic lines, making them analogous and not homologous traits.⁷ By “filling in” the blank spaces of the past with clues from fossilized fungi, we can develop a better understanding of not only how long fungi have been filling certain ecological roles, but also when major fungal lineages diverged. Through the differences between ancient fungi and their modern counterparts, we can start to grasp when certain traits evolved and ultimately learn about the true evolutionary relationships among modern fungal taxa.

Beneath Notice

A dispatch from your editor, Kathie T. Hodge

Kent Loeffler and I are headed up to Rochester, NY on Monday to give a presentation on our explorations of fungal photography using a borescope. Should be awfully interesting to talk to a mix of optics professor types and mushroom-lovers. We’ll bring part of our borescopic art show along, and also, ta da! Our new self-published book, Beneath Notice: Adventures with a borescope.

Since I am not the first author and can therefore cast humility aside, let me tell you that this is a beautiful book. Not only are the small fungi it features surprising and lovely in their own right, but the book design by Noni Korf is strong and handsome. The book is essentially a catalog of two years of our well-received art shows. It includes all Kent’s borescope photos from our shows (with a few bonus additions), along with wry and moderately informative captions by me, Kathie Hodge. There’s a brief explication of borescopy and the trials of using a borescope in the field. Apparently few have bothered to to use a borescope to capture beauty; the borescope has previously been relegated to inspecting gun barrels, fuel injectors, moldy walls and the insides of people’s knees. It’s a 90 page, softcover book and I respectfully submit that it’d make a good gift for anyone fond of fungi or intrigued by life on a smaller scale. You can order it from Lulu Press, right here.

Order Beneath Notice: Adventures with a borescope., $33.50

Homeward Bound: Fungi of China

notes on fungal diplomacy by Kathie Hodge

It’s been an exciting week. On April 13, 2009, we held a ceremony to give a set of very special Chinese fungi to the people of China. We’ve been taking care of these fungi for a long time–since about 1940. They have a poignant story tied to the brave heart and scientific dedication of S.C. Teng. He was a graduate student at Cornell in the 1920s, and went on to become one of the fathers of mycology in China. You can get a sense of the determination of the man from this Associated Press article. A little more about Teng is in this 2005 article (PDF) from our Department Newsletter.

The Fungi of China is a special collection of the Cornell Plant Pathology Herbarium (CUP). As Director of the Herbarium, I am in charge of something between 300,000 and 400,000 specimens plus about 60,000 archival photos. My Curator Robert Dirig is the one who does all the hard work. Many treasures make up our collections, including the mushrooms of George F. Atkinson, over 7000 type specimens (the first of their species to be named; bearers of the names of their species), the occasional seashell, and a lot of other things we love or have barely even noticed.

The guest list for the April 13 repatriation ceremony was impressive. Presiding was Madame Yandong Liu, State Councilor of China and China’s highest ranking female official. The delegation included Mr. Ji Zhou, Minister of Education; Mr. Xueyong Li, Vice Minister of Science and Technology; Mr. Wenzhong Zhou, the Chinese Ambassador to the US; and many other high ranking and accomplished Chinese leaders. With the help of a translator, Cornell’s President David Skorton read a carefully crafted letter pledging our gift, and Madame Liu read back her letter of acceptance and appreciation. Pretty elevating.

Now take a break and give yourself a tour of our photo gallery of some of the Fungi of China specimens. The images were created by Kent Loeffler (Photographer, Department of Plant Pathology and Plant-Microbe Biology). The problem is, herbarium specimens aren’t beautiful things. The Associated Press quotes me as saying they often look like “something you would sweep off your kitchen floor,” which I can’t believe I actually said. We know better, of course, because up close they are heart-breakingly ordered and organic and exquisitely functional and dear. I asked Kent to photograph the fungi in a way that shows them in their best light, and I think you’ll agree he’s been quite successful. Kent’s photographs, printed up handsomely large, are another part of our gift to China.

So our gift to China is 2278 specimens, out of about 2300 that we hold. The difference is in specimens that could not be divided without destroying them, which we’ll keep at Cornell. We make this gift freely, out of good feeling. China has a most impressive group of taxonomic mycologists–the group within the Chinese Academy of Sciences forms one of the largest and most productive mycological centers in the world. We hope our gift will facilitate an understanding of the diversity and systematics of Chinese fungi by Chinese mycologists, who will now have much easier access to study these historic specimens.

What will happen next is not quite settled yet. We expect that during an upcoming visit of President Skorton to China, the 2278 specimens will be handed over in another splendid and solemn ceremony in Beijing. In the meantime we’re feeling both proud and humble to be a part of it.

Some news coverage and more info

• Associated Press news release by Ben Dobbin (Photos by Heather Ainsworth). This is the story that appeared in over 400 news outlets worldwide, like here (often filed under “strange,” alas)
• Xinhua news service story
• Cornell University News story
• National Public Radio’s interview with our own inestimable Professor Emeritus Richard P. Korf
• National Geographic News
• Kent Loeffler’s photo gallery of selected Fungi of China specimens

• Early article about the repatriation and Teng’s travails published in the Dept of Plant Pathology newsletter, 2005. [Plant Path Newsletter article, 2005]

Entomophaga maimaiga – The caterpillar killer

This post was written by a fan of moldy bugs who is a graduate student in Entomology at Cornell.

The Cinderella story of biological control is the introduction of the fungus Entomophaga maimaga (Zygomycota: Entomophthorales) to control gypsy moth caterpillars in northeastern North America. The gypsy moth became established here in 1869, and its fuzzy caterpillars eat the leaves of a wide range of plants and trees (though they prefer oaks). The gypsy moth quickly became a pest and began to cause serious forest defoliation as populations reached extraordinarily high densities in the absence of serious natural predators (aside from generalist insectivores). In 1910 and 1911 fungal pathogens were released, one of which was E. maimaiga, but no resulting infections were found in the larval population and hope for a fungal solution was given up as a lost cause.

Seventy years later, scientists decided to try again, and E. maimaiga was released again. Just as before, however, no lasting infection was found in the field. Then, in southwestern Connecticut in 1989, large numbers of Gypsy moth larvae were found to have succumbed to a fungal pathogen, specifically E. maimaiga¹. The fungus has been seen most years since then, and is has spread through northeastern gypsy moth populations. How could this fungal pathogen have taken so long to establish itself? As much as scientists and biological control advocates would love to take the credit for this introduction, genetic and geographic evidence point to the fact that this new epizootic (the animal equivalent of an epidemic) was caused by an accidental introduction of Entomophaga maimaiga. Whoops.²

Here’s the part of the Entomophaga maimaiga life cycle that’s visible to the naked eye. This is also the part that makes it a potent biological control. The time lapse movie below is courtesy of James Reilly.

Quicktime 5+ movie

Time lapse video of our fungus, Entomophaga maimaiga, erupting from the corpse of its host to shoot spores all over the place. Movie by James Reilly.

What you’re seeing here are the late stages of infection. The fungus has eaten away the inside of the caterpillar and will now send out white structures called conidiophores, from which its spores are shot into the air. These spores (asexual conidia) can now infect other caterpillars. If it fails to find a host, a conidium can germinate to make and shoot off a smaller replicate of itself (spiffy!). Spore dispersal allows for direct infection of other caterpillars within the area, but conidia are short-lived and only capable of surviving for a few days in the environment. They’re hoping to land on a caterpillar. From there they’ll grow through the cuticle and start eating up its tissues (think Invasion of the Body Snatchers). Once it’s finished its gypsy moth caterpillar (and this fungus eats nothing else), the fungus bursts back out to produce a new crop of spores. In the video we see the fully colonized corpse shrink as its biomass is converted into fungus. For the pyrotechnic finale, a white dust of spores appears–each spore is independently shot from its mother cell. In the second half of the video, we see the same thing at higher magnification. The conidiophores emerge like small, gooey cauliflowers, and become sprinkled with salt (conidia) that are then shot off. The conidia then accumulate on the hairs like white crystals. By the time we’re done, there’s virtually no fungal biomass left in the caterpillar; it’s all been shot away.

How does this fungus overwinter if these spores are ephemeral and the supply of caterpillars runs out? Towards the end of the season, or towards the end of the larval stage of the caterpillar, E. maimaiga produces hyphal swellings within the insect’s hemocoel (space in the insect that the blood or hemolymph sloshes around in). These swellings develop a thick wall and become asexual resting spores. They can survive for years in the soil litter (where most caterpillar cadavers end up). When presented with favorable conditions, they can germinate to make and shoot off conidia of their own, thus starting up the cycle of infection once again.²

Entomophaga maimaiga is perhaps one of the most successful fungal biological control agents. It belongs to the order Entomophthorales, many members of which are insect pathogens, including our fly-killing friend Furia ithacensis. Entomophaga maimaiga can effectively control outbreak populations of the gypsy moths and has spread to cover most of area inhabited by these moths. Only at the edge of gypsy moth spread is this fungus not present.

Shots from the archive: puffball lad

Well hello. It’s been quiet here for a while, hasn’t it? Things are thawing now and I’m really looking forward to a new mushroom season. I’m sure you are too.

In the meantime, did you know that we have a really big archive of cool old photographs here? This is one I have blown up and hanging on the wall of my lab. It was taken in 1937 by our then department photographer, W.R. Fisher. We’ve been fortunate to have several generations of expert photographers associated with my Cornell department–explore our photographic heritage here. We’ve already talked about the puffballs here, and I can tell you nothing about the lad (I’m a mycologist!).

Part of my job is to direct the Cornell Plant Pathology Herbarium. In addition to a few hundred thousand specimens of fungi and sick plants, we have about 60,000 photos in our archives, going back to the 1880s. Many of them are interesting or odd. I’ll be posting some here, but feel free to explore on your own.

borescopic mycology

I’m proud. Proud to tell you about our new art/science show at Mann Library. It features the staggering borescope photographs of Kent Loeffler (official Blog Photographer), along with the jocular science-ish musings of me, Kathie Hodge. The borescope reveals a new perspective on fungi: A bug’s eye view. My friends, the borescope will reveal to you a whole world you have never seen before.

Through the end of February you can find our show hanging in the second floor gallery of Mann Library, on the Cornell campus in wintry upstate New York. Alongside are our famous time lapse videos, looping on a high definition monitor. You’ll want to come back again to help us celebrate at our curiously belated opening reception on Feb. 5, from 5 to 6pm.

• Jan-Feb 27, Beneath Notice Borescopic photographs by Kent Loeffler; fungal outbursts by Kathie Hodge (Mann Library 2nd floor Gallery)
• Feb 5, 5-6 pm, Beneath Notice Reception, Mann Library 2nd floor Gallery

Our show is loosely a part of Ithaca’s Light in Winter, a festival poised at the interface of art and science. Well, that’s my favorite place to be!

But wait, there’s more! For Light in Winter we’ve also put together a special Jan 25 event for the main Light in Winter festivities this weekend:

• Jan 25, 10am, Little Fungi for Good and Evil, a talk and slide show by Kathie Hodge (Mann Library lobby; all audiences)
• Jan 25, 10-12am, Fungus Amongus, by Dave Kalb and gifted others (Mann Library 2nd floor Gallery; kids and grown-ups)

This is a public outreach kind of event. You get to come and look down a microscope or two, have a look at our fungusy displays, and ask all those fungus-related questions you’ve been saving up. Hope you can make it.

Rumor has it there will be zoospores in the library! Don’t tell the librarians, for goodness’ sake.

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