Wednesday, November 27, 2013

Some Fungi You Should Be Thankful For

Ahem... For which you should be thankful.

Here at the PDIC we focus on the negative impacts of fungi, bacteria, nematodes, and viruses on plant health and human well-being. This tends to overshadow the fact that they do more good than harm in the grand scheme of things. Since we deal mostly with fungi, I offer several for which we should be grateful.

Saccharomyces cerevisiae helping in the kitchen.
Saccharomyces cerevisiae. The lowly baker's yeast is one of humanity's best friends in the fungal kingdom. It's a one-celled organism, whereas most fungi grow as thread-like "hyphae". More importantly, it's capable of fermentation, a process that starts with carbohydrates such as sugar and results in energy for the fungus and alcohol and carbon dioxide as byproducts. Without the yeasts, the rolls and stuffing on the Thanksgiving table would be unleavened, and there simply would be no wine, beer, or spirits at the celebration.

Mycorrhizal fungi at work, under the surface.
Plant Pathology Department Slide Collection
Mycorrhizae. When we look at a plant, we don't usually think about the roots. Even when we do think about roots, we usually forget that most plants partner-up with certain fungi that enable them to better extract nutrients from soil. This association is known scientifically as a "mycorrhiza" (plural "mycorrhizae"), which is simply Greek for "fungus-root". Other benefits have been ascribed to this relationship such as increased resistance to root diseases and other stresses. There are two basic groups: the ectomycorrhizae and the arbuscular mycorrhizae. The former are characteristically associated with trees and form a fungal mantle on the outside of the root, slightly modifying its structure and appearance. Often these fungi produce mushrooms or puffballs (above or below ground) when it comes time to reproduce. A good example is the small, reddish Russula mushroom we see popping up each fall in our area. The arbuscular mycorrhizae form on both herbaceous and woody plants, and are very inconspicuous. If you aren't a scientist dedicated to plant roots in some way or another, you probably won't ever notice them. Do appreciate them, though, as they are close collaborators with the plants we so value and need.

Brown cubical rot of pine wood, caused by the fungus Meruliporia incrassata.
Plant Pathology Department Slide Collection
Wood decay fungi. Yes, wood decay fungi are unwelcome when they invade living trees or our homes, but we’d be in deep trouble without them. They are a critical cog in the carbon cycle, degrading the cellulose and lignin components of wood. In fact, fungi are the only organisms in the world that produce the enzymes necessary to break down lignin. Without them we would be up to our eyeballs in woody debris. There are a number of spin-off benefits, as well. For example, pulping using these fungi will be better than current processes in terms of reducing both energy use and chemical waste.

Fungi with medicinal applications. We remember with gratitude the mold Penicillium, which brought about the antibiotic revolution. Apart from the penicillins, the cephalosporin antibiotics can also be traced to a fungal metabolite. The cholesterol-lowering drugs compactin and lovastatin are derived from fungal fermentation, although other statin drugs are synthetic or semi-synthetic. Traditional Chinese medicine makes use of a number of different fungi, some of which may find their way into the western pharmacopeia.

Agriculturally important fungi. Several fungi such as Beauveria bassiana and Metarhizium anisopliae are used as biological insecticides. Some such as Trichoderma harzianum are found in biological fungicides. Also, an important group of chemical fungicides, the strobilurins, were developed based on a chemical found in the mushroom Strobilurus tenacellus.

Farmed, or Farmer?
Neocallimastix and company. Probably the most obscure group on the list, it was only within the last forty years that these were recognized as fungi and not protozoans. This includes genera with such names as Orpinomyces, Piromyces, and Neocallimastix, Once known as the "rumen chitrids", they are better called "anaerobic gut fungi", "anaerobic zoosporic fungi", or simply "anaerobic fungi". They work together with bacteria and protozoans in the digestive systems of many kinds of herbivores to break down the fibrous diet of these animals. They are found in the rumen of animals such as sheep and cattle, but have also been found in deer, horses, kangaroos, even rhinos and elephants. They do a better job than bacteria at breaking down lignocelluloses, and their rhizoids can get through plant cuticles, which bacteria & protozoans cannot penetrate. We really should be thinking of cows as farmers, responsible for a large and diverse population of microbes that convert roughage into materials that the cows can metabolize.

Strawberry jelly ingredients. Where does the citric acid come from?
Agaricus bisporus and other edible fungi. These are probably what you first think of when you consider "good" fungi, though their contributions pale in comparison to the others listed above. Note that the portabella and crimini represent a strain of Agaricus bisporus, the same white button mushroom of pizza fame. Of course there are many other wonderful edible fungi out there. A number are more popular in oriental culture than in the west, but you've probably eaten Auricularia in oriental soups. You may not be aware, though, of your consumption of a product that is commercially produced using the mold fungus Aspergillus niger: citric acid. The next time you see "citric acid" on the label, think fungus rather than lemons! And whatever you eat, have a Happy Thanksgiving!

Read on to find out about Insects to Be Thankful For.

Some Insects/Arthropods You Should Be Thankful For

How much of this delicious bounty was influenced by beneficial arthropods?

As we sit down this Thanksgiving to our turkey, mashed potatoes, and stuffing (and of course gravy!), we often give thanks to various people and things that make our lives better. So in that tradition, here are some of the insects and other arthropods (in no particular order) that, throughout the year, enrich our gardens, homes and lives...many of which we would not normally acknowledge.

Paper wasps, hornets & potter wasps (Vespidae)

Paper wasps (Polistes sp.) may sting, but they also hunt down pestiferous caterpillars to feed to their young.
Though largely hated due their painful stings and sometimes aggressive nature, these wasps are very good at hunting soft-bodied insects in gardens. Their favorite food seems to be caterpillars, which are the bane of most garden plants. The truly social groups (paper wasps & hornets) have an entire colony to feed, so they often carry away numerous pests. However they also need to defend their many sisters, thus their stings. Maybe I should focus on potter wasps (Eumeninae), who are solitary but also provision their mud pots with several caterpillars for their young to feed on. While they can sting, they are not aggressive like their social cousins. There are also several groups of solitary hunting wasps (Sphecidae) that give their young paralyzed caterpillars, further solidifying wasps as beneficial predators.

A potter wasp's (Eumeninae) pot is getting ready to dry. The small hole in the top is big enough for mother wasp to add a number of paralyzed caterpillars before sealing it off for her young to feed.

Parasitic wasps

A minute wasp (Aphelinidae; approximately 1 mm long) perches on its tiny host - a scale insect.
These usually minute wasps don't sting us, nor are they often seen by us. However, their effects on pests are immeasurable (figuratively - there are certainly studies that have been done to measure their impact). Most lay eggs within a host, which hatch into tiny larvae that feed on the poor organism from the inside. Others attach to the outside of the host, slowly sucking it dry. There are several groups of Hymenoptera that do so, including the large superfamilies Ichneumonoidea (Ichneumonidae & Braconidae) and Chalcidoidea (many families). Along with wasps several other groups of insects, notably flies (the family Tachinidae for example), have members that parasitize pests.

This hornworm caterpillar (Sphingidae: Manduca) is on its last legs. Its parasites (a species of Baconidae) spin white cocoons after emerging, from their host.

Pollinators (and not necessarily the ones that come to mind)

This false blister beetle (Oedemeridae: Heliocis repanda), like many beetles, loves nectar and thus also comes in contact with pollen which it may transport to many flowers.
I am sure you have already thanked butterflies and bees (both honey and bumble) for pollinating the plants we need to survive and enjoy looking at. However, there are numerous other insects that transfer pollen from flower to flower. Beetles, flies, bugs and even earwigs can be pollinators . In fact, any insect that visits flowers has a chance to pollinate. One of my favorite pollinators (as it should be yours as well) is a genus of tiny little biting midges (Ceratopogonidae). Without some of these [sometimes nasty] flies, we would not have one of life's greatest foods - chocolate! These flies are the only things that pollinate the cacao plant (Theobroma cacao), being small enough to fit inside the diminutive flowers.

Even earwigs (Dermaptera) enjoy nectar and pollen every once in a while. This one is covered in pollen which will likely rub off on another blossom, propagating the plant.


Larval black soldier flies (Stratiomyidae: Hermetia illucens) are powerhouses of decomposition, frequently obliterating compost waste.
Yes flies (Diptera) are sometimes annoying. And many transmit diseases or are pests. However, a large percentage of flies breed in decaying organic matter as larvae. This huge clean-up crew is responsible for devouring both rotting animal carcasses (which would be fun to have hanging around, right?) and vegetable matter. Proof of the latter can be easily seen by those who compost their yard waste and table scraps. Without flies we would be knee-deep in a putrid, bacteria-ridden mess - not something that would be good for your Thanksgiving appetite. Some flies are also important predators or biological control agents of weeds, to name a few good deeds done on two wings.

Energetic and beautiful, long-legged flies (Dolichopodidae) scour leaves to hunt down small insects including many pests.

Dung beetles

Even small dung beetles like this Onthophagus tuberculifrons can help bury dung and keep the ground clean.
As with flies cleaning up decaying matter, dung beetles get rid of another resource we find disgusting - excrement! These busy beetles (mostly Scarabaeidae) eat and bury dung for their young to feed on, effectively removing the foul substance from the ground surface. This has long been know to aid in pasture health by allowing grass to grow, aerating soils, destroying the breeding grounds of pest flies and worms, and returning nutrients to the soil. Instances where dung beetles are lacking have proved highly detrimental to natural and production ecosystems. Some are also quite beautiful and have amazing behaviors too.

The rainbow scarab (Phanaeus vindex) is one of our most beautiful beetles, despite spending a large amount of time covered in dung or underground. This male also has an impressive horn.

House centipedes

Although only a wee baby, this house centipede (Scutigeridae: Scutigera coleoptrata) is a fierce predator in the home.
Surprised by this? Despite their frightening speed and creepy leggyness, these centipedes (Scutigera coleoptrata) are good at hunting down and devouring household pests like flies and cockroaches. Though venomous, they rarely bite and most often use the venom to subdue things you really should be afraid of.


This fire ant (Solenopsis) is removing soil from its nest. Colonies of fire ants can be a good thing for your garden.
Again, although there are some ants that are not so great - those that sting and tend pest insects come to mind - many species of ants are very good at cleaning up waste, planting seeds and eating pests. For example, though fire ants are loathed for their stings, they can be very effective predators of crop pests. They are also effective, like earthworms and dung beetles, at aerating and churning massive amounts of soil.


Just kidding! There is really nothing good I can say about ticks. Though I respect them for their fortitude and tenacity, there is really no good reason for them to exist except to suck blood and transmit diseases (which they really can't be blamed for - pathogens just love to use ticks to spread).

Final thought
There are many arthropods that directly or indirectly benefit us and the ones listed above are just a starting point. Almost every group can have some quality that deserves our thanks - you just have to observe them in your garden or read the latest information to get a good idea of who the good guys are. It is also good to remember that "beneficial" is in the eye of the beholder - the advantages of arthropods must be weighed with the situation (e.g. some pests can be beneficial and vice versa).

Wednesday, November 20, 2013

Uninvited Holiday Guests

Insects, like all animals, must survive the winter (in one way or another) to reproduce the next year. There are two main strategies to do so: migrate or "hibernate". Of course there are famous insect migrations including monarch butterflies (Danaus plexippus) and several species of dragonflies (Odonata). However it is much more common for insects (and other arthropods) to hunker down for the winter in a nice secluded place. Insects overwinter in different life stages - either as eggs, larvae/nymphs, pupae (if they are holometabolous), or adults. The stage that overwinters usually depends on the type of insect, but sometimes can be determined by environmental or geographical factors.

Thus, as the days begin to cool and darkness descends earlier in the evening this holiday season, you may be getting more than your in-laws invading your home. Most do so by finding a nice brightly-colored home as a landmark during warm days where they aggregate on the siding, in eaves, or along windows. The most common nuisance insects overwinter as adults that may become active within homes during warm days of the season - a common occurrence here in NC which has a mild, fluctuating winter. Mass movements of these insects into living areas can be difficult to deal with and are a real annoyance. The following are some of the more common insects to enter houses.

- True bugs (Hemiptera) - the worst offenders -

Kudzu bugs aggregating in the crack of a tree; could easily be a window or the gaps in the siding of a house.

Bugs are among the most common insects found aggregating on and entering homes in the cooler months. Their numbers and the pungent smell they produce (they're not called stink bugs for nothing!) can be bothersome to people that want to enjoy the comforts of their indoors. Although bugs are generally harmless, kudzu bugs (Plataspidae: Megacopta cribraria) are sometimes known to cause irritations on skin, brought about by the secretions they produce. Brown marmorated stink bugs (Pentatomidae: Halyomorpha halys), another recent introduction into the US, also find it nice and cozy in houses. Along with these invasive bugs, many other types, including leaf-footed bugs (Coreidae: Leptoglossus) and boxelder bugs (Rhopalidae: Boisea trivittata), enjoy breaking and entering for a nice place to hibernate.

Kudzu bugs: one is alright, but hundreds are bad news!
Brown marmorated stink bugs find your home when it's cold outside.
Leaf-footed bugs may be seen around the home.

- Flies (Diptera) - can we use your attic? -

Figure from Oldroyd's magnificent book, The Natural History of Flies (1964). 

Several groups of flies will spend the winter in attics, barns and other man-made structures, safe and cozy away from the elements. The most common are called cluster flies (Calliphoirdae: Pollenia sp.), named for the fact that they often "cluster" in groups of hundreds in the attics of homes. Normally they are out parasitizing earthworms, but in the fall and winter when things slow down they get the urge to swarm homes. Face flies (Muscidae: Musca autumnalis) will also do this, usually around areas with livestock, their primary food (larvae live in dung and adults feed on facial secretions). On warm days these flies may come out of hiding to stretch their wings, much to the dismay of homeowners.
Cluster flies are drab (for blow flies) and have golden hairs on their thorax.

- Ladybugs (Coccinellidae) are pretty - but get them out of my house! -

"Ladybugs are great, right? They eat all the pests and are nice to look at." Tell that to someone whose living room is overrun by these red and black beasts. Most ladybugs do a fine job of staying outside and being good neighbors. However, one species in particular (though there are a few others) - the multicolored Asian ladybug or harlequin ladybug (Coccinellidae: Harmonia axyridis) - loves to come into homes. This highly variable species was first introduced into the US in 1916 for the control of pests and has been readily available for farmers and homeowners to purchase. In the 1980s it finally became established, and is now the dominant ladybug in much of its range. Thus there have been some concerns about this species. First, it may be pushing out native ladybugs with its voraciousness, which is not good for our biodiversity. Second, it can be structural nuisance pests. Along these lines, when they do enter homes in large numbers they can sometimes bite people and, like many ladybugs, reflexively bleed a noxious substance that may cause skin irritation and allergic reactions. For both of these reasons, the cartoon-like insects can be less funny than they are nightmare inducing.

Multicolored Asian ladybugs, though sometimes beneficial, are often a nuisance.

- So what can you do about it? -

The best way to deal with these insects is to first make sure that they cannot enter your home. Search for cracks and holes in the siding or under eaves. Any crack or hole small enough for the average insect to enter should be repaired or covered. While pesticide sprays on the South sides of the home may kill or deter some insects, they are not long-lasting, nor are they particularly effective. Once in the home, it is best to vacuum the insects up and collect them into hot soapy water or freeze to kill them. Spraying indoors usually does more harm than good, so cultural practices mentioned above work best.

Tuesday, November 5, 2013

About that pumpkin....

So Halloween has come and gone, but it's still Fall (Thanksgiving's on the way!) and everything is already red, yellow and orange. Why not keep that pumpkin spirit going?

Happy pumpkins are just glowing! (Photo by Matt Bertone)

Unfortunately, chances are by now your pumpkin is looking more like this:

This pumpkin used to be happy. (Photo by Sara Prado)

If you're lucky you can get it to the trash or compost without the bottom falling out (I wasn't that lucky). Even if you didn't carve a scary face in it, it will likely be in decline seeing as it is a fruit off the vine and it is slowly being broken down by bacteria and fungi. If there is a wound on the pumpkin from rough transport, it opens the pumpkin to these microorganisms. This is prime food for many insects that love to eat the nutritious soup.

Most of these insects are flies. Flies love rotting vegetable matter. Vinegar or fruit flies (Drosophilidae) are particularly fond of rotting fruit. Some walk all over their giant bounty, waving their patterned wings around while seeming to dance. They do this to attract mates and establish that they have found a nice source of food for their precious little maggots.

This vinegar fly (Drosophilidae: Chymomyza amoena) may have a dance party on your over-ripe pumpkin.

Other common flies include dark winged fungus gnats (Sciaridae) whose larvae love to eat the molds and other fungus growing happily on the pumpkin flesh. The small black flies swarm around the pumpkin and settle after a disturbance.

A mating pair of dark-winged fungus gnats (Sciaridae) - a scene you may see on your rotting pumpkin.

Many other fly species may be found among the decaying Jack-O-Lantern as well. However, flies aren't the only visitors to such a great source of food. Beetles, earwigs, isopods (sowbugs & rolly-pollys), slugs/snails, and other organisms like this type of substrate to feed on as well.

Picnic beetles (Glischrochilus) and other Nitidulidae love rotting vegetation. This is from last year's pumpkin.

Isopods may nestle themselves inside or under the pumpkin to feed.

"I am looking for a nice moldy pumpkin pie" says the snail. Slowly, he might find yours....

Of course, if you are responsible and discard your pumpkin while it is still fairly fresh, you won't have to deal with these insect and other small animals. But then again you may not see some of these cute little critters setting up shop and recycling your autumnal fruit festivity. Oh well, they can find the compost bin too I guess...