Trouble for the Sweet Green of the South

Collard greens are a staple of southern cooking. Slow cooked with the salty flavor of ham hocks and served up with golden corn bread, collards make the perfect meal for a cool winter’s day. Collard greens belong to a group of loose-leaf cultivars (non-heading) of Brassica oleracea. Other members of Brassica oleracea include cabbage, broccoli, Brussels sprouts and cauliflower. These leafy greens are believed to have descended from Asian wild cabbages and eventually made their way into Europe where ancient Greeks and Romans grew the plants in domestic gardens over 2,000 years ago. When colonists settled in the New World, greens were a major part of any well-rounded vegetable garden. In the South, collards were abundant and cheap and quickly became a main ingredient in soul food inspired dishes that southerners still enjoy today.

Lately, we have seen quite a few collard and cabbage samples in the clinic. This season, white mold has been quite prevalent in both home gardens and commercial fields. White mold is caused by the soil-borne fungus Sclerotinia sclerotiorum. This disease is favored by cool, wet conditions and most infections occur in late winter to early spring. Early symptoms of the disease are tan, water-soaked, circular areas on the leaves or crown. These areas quickly become covered in fluffy white fungal growth, followed by a watery breakdown of infected tissue. Eventually, the fungus completely colonizes the head and produces large, black, seed-like structures called sclerotia.

White mold (Photo: E. Lookabaugh)

Sclerotia can survive in the soil for many years. Cool, wet conditions trigger the sclerotia to germinate. Sclerotia can germinate to form mycelium that directly infects plant tissue, or to produce small cup-shaped apothecia (fruiting bodies). These small, mushroom-like apothecia are most likely to form when the sclerotia have been exposed to cold, saturated soil for several weeks. They produce millions of ascospores that can be windblown to nearby plants and infect.

Germinated sclerotia with mushroom-like apothecia (Photo: H.D. Shew)

Sclerotinia sclerotiorum has a very wide host range and can attack over 350 species of plants. Common vegetable hosts include cabbage, broccoli, cauliflower, Brussels sprouts, lettuce, pepper, bean, pea, potato, and tomato. Field crop hosts include sunflower, canola (rapeseed), and soybeans. Additionally, several species of weeds are hosts, including ragweed, dandelion, wild clover, vetch, common chickweed, and pigweed.

Sclerotinia on field grown broccoli (Photo: B. Shew)

Controlling white mold can be difficult and requires an integrated approach. Maintain good air circulation by using proper plant spacing and selecting varieties that have minimal leaf overlap between adjacent plants. Maintain good soil drainage by planting in raised beds. Planting susceptible plants in areas with a history of white mold is not recommended. Rotate with non-susceptible plants such as small grains (rye, wheat), corn, beets, onion, and spinach to prevent inoculum build-up. Only very long rotations (4 years or more) will be helpful in areas with high inoculum levels. Practice good weed control strategies to remove weedy hosts from the area. Planting a small grain as a winter cover crop may help to exclude winter weed hosts. Deep plowing or turning of the soil can be useful because sclerotia typically do not germinate at soil depths greater than 5 cm. This is only effective for one year as subsequent tillage will bring the sclerotia back up to the soil surface. Avoid spreading the fungus with equipment or on infected planting material. When practical, remove infected plants by bagging and burning or disposing of offsite. Do not place infected plants in nearby cullpiles as these can become sources of inoculum. Avoid overhead irrigation and use subsurface irrigation when possible. There are no chemical control options for the home gardener. A few products are available to commercial producers, but correct timing of sprays is critical for successful control. See the Ag Chemical Manual for more information on chemical and cultural control of this disease.

For information on Sclerotinia-caused diseases of other hosts, see our previous blog post.

For information on another disease of collards, see our post on black rot.

Winter Insects and a Spring Foreshadowing

With the extreme cold snap and the slow march of winter, most people think that insects and other small animals would be too chilly to make an appearance. Their diminutive size might lead one to think that they would freeze solid out in the environment. For the most part that is true: insects tend to either hibernate or migrate during this time of year to avoid extreme cold. But what about those that enjoy the cold? Many groups only come out this time of year and have special adaptations (such as natural antifreeze - apparently common in Arctic species) to survive the low temperatures. Here are a few cold-loving groups that come to mind:

• winter crane flies (Trichoceridae) - a family of mosquito-like flies related to their warm weather cousins, the true crane flies (Tipulidae); you may have seen them at your porch light
• winter stoneflies (Taeniopterygidae) - develop in well-oxygenated streams especially in the mountains; they emerge in the fall, winter and early spring
• snow crane flies (Tipulidae: Chionea sp.) - these small, wingless, spider-like flies only come out in cold weather, usually being observed on snow
• snow scorpionflies (Boreidae) - these tiny, hopping insects are only found in the Northern Hemisphere, most commonly in mountainous areas with snow; their larvae feed on mosses
• snow fleas (Hypogastrura) - often seen in masses on snow, these tiny springtails (not true fleas) enjoy the cold weather
• some dung beetles (Scarabaeidae) - in my studies on the seasonality of dung beetles in NC, I found that a few species were only present in the cooler months of the year (below)

Aphodius distinctus is one of the dung beetles that is present in the fall and winter, but not during other times of the year (from Bertone 2004).

More types of insects than you think are active in the frigid times of the year*. Most go unnoticed (maybe because we are inside more) and pass their days doing what they do and not bothering us.

Others are a sign of what's to come. Despite their autumnal name, the fall cankerworm moths (Alsophila pometaria) have been out and about for a few months. In fact, just two weeks ago I was alerted to a plethora of females mistaking some campus building pillars for trees. The wingless females were clinging to the cement and some had started to lay their eggs. No doubt others had already done so since they appeared in the late fall.

Female fall cankerworms are strange moths that lack wings (though not unique among Lepidoptera).

The tiny, barrel-shaped eggs of the fall cankerworm laid in a nice batch.

I was also surprised by the abundance of male fall cankerworms at lights and elsewhere this year - something I have not particularly noticed in the past. Males, unlike the wingless females, have large, drab wings and look...rather moth-like and fairly mundane.

Male fall cankerworms are fully-winged and can be found at lights during the cooler months.

So what does this mean? I am assuming the abundance of adults is a direct result of the previous spring's many, many larvae that plagued local trees and bushes, raining down from above on silken strands. But does that mean that we will have as many (or, even more) this coming spring? I am not sure, but we will know in a few months when these little guys come out:

Fall cankerworm caterpillars are all too familiar "inchworms" in recent years.

Oh, and don't forget about spring cankerworms! The silver lining? At least it will be warm outside.

*there is even a whole group of insects, the ice crawlers (Grylloblattodea) that only exist in the cold mountains of the Northern Hemisphere, though in the US only in the Western part of the country; they cannot live much above freezing and will die sitting in a person's hand!

Nematodes Chilling Out Now, But Ready for Action

Nearly dead liriope plants with crown rot and root-knot nematodes.

Last week we received a sample of liriope from NCSU’s Centennial Campus. The main problem was Fusarium crown rot, but it also suffered from root-knot nematodes (Meloidogyne). Based on a microphoto I took, Dr. Weimin Ye of the NCDA&CS Nematode Assay Laboratory gave a tentative identification as the southern root-knot nematode, Meloidogyne incognita.

Root-knot nematodes are microscopic roundworms that are parasitic on cells found in plant roots. The nematodes have a spear-like stylet that allows them to pierce the root cells and feed on the nutrients found there. Root-knot nematodes also use the stylet to inject the cells with nematode "saliva" which contains substances that, among other things, cause the cells near the nematode's head to swell. This swelling eventually leads to the galls that are a symptom of root-knot nematode infection.
  
You may be surprised to know that we’ve found root knot nematode damage on samples from every month of the year, although about 80% of them arrive between mid-May and the end of October. In a blog post last month, Dr. Barbara Shew made mention of this particular pest in the context of the relatively unknown “Nematode Song”.

Meloidogyne species have an extremely wide host range. The PDIC has made a confirmed or suspected diagnosis of root-knot nematodes on many North Carolina host plants since January 2008. This list is by no means exhaustive. For example, figs are a known host that did not show up during this period.

Ajuga, Angelonia, Aucuba, Azalea, Beans, Beets (garden & sugar), Begonia, Bermudagrass, Boxwood, Butterfly-bush, Cockscomb, Coleus, Gardenia, Corn, Cotton, Creeping bentgrass, Cucurbits (Cantaloupe, Cucumber, Watermelon), Euphorbia, Foxglove, Hydrangea, Impatiens, Itea, Japanese holly, Lantana, Liriope, Okra, Pansy, Peach, Peanut, Pentas, Potato, Sasanqua camellia, Soybean, Spinach, Strawberry, Sweetpotato, Tobacco, Tomato.

Plants listed in bold are those with three or more diagnoses during the last six years. The plants most often diagnosed were boxwood (6 samples), cucumber (7), tobacco (5) and tomato (12). Of course this is due in part to the popularity of these plants in North Carolina.

Not all species of Meloidogyne are created equal. For example, all four of the most common species can reproduce on tomato, but only two of them are problems on peanut. Even within species there are races that differ in their host ranges.

Rather than repeat the very useful information on root-knot nematode damage and control from Charlotte Glenn’s previously cited article, I’ll just add a few comments. One is that if your interest is bedding plants, the University of Florida has a publication showing the relative susceptibility of various cultivars.

Charlotte mentioned how to tell a root knot from a legume nodule. Another challenge can be distinguishing between root knots and the normal storage swellings on roots of plants such as daylily, liriope and mondograss. In my experience, the average tuberoid swelling is larger than a root knot, but gall size can vary with the host plant. When in doubt, you can do a dissection under a magnifying glass or a stereomicroscope.

Root-knot galls (left) and swollen storage area (middle) on liriope roots.
The tip of a standard pencil (right) is for size comparison.

Choose swellings that are solid, then shave or pick off layers with a scalpel or razor blade. Look for the pearly white swollen posterior of the adult female nematodes. They are easily “popped”, so work carefully. With a little more effort you can lift out the entire nematode and see the narrowed head and esophageal region.

Two root-knot nematodes dissected out of their gall (arrows).
One is in hind view, the other in side view. Scale bar=0.4mm.

An interesting point to ponder at this time of year is how nematodes survive the “big chill” of January, especially in the absence of a host plant. The short answer is: eggs. Adult females are pretty much egg-producing machines, extruding them in a gelatinous matrix throughout the growing season. Egg masses can be seen on the gall surface if you look under magnification before washing the roots. They may be brown or white.

Brown masses on the surface of these galls are nematode egg masses.

An important part of the nematode’s reproductive “strategy” is that not all the eggs hatch as soon as conditions become favorable; some remain inactive. This inactive period is known as diapause and confers a survival advantage: if conditions improve only temporarily, the unhatched eggs will survive. Fortunately for our plants, root knot eggs will not survive more than about one year if they can’t hatch and infect a susceptible plant root. In this week’s sample, eggs at different stages of development could be seen in the same mass. Some eggs showed no signs of further development, while others already had active juvenile worms inside. In the photo below, you can even see the stylet of the unhatched juvenile. If you have doubts as to whether this nematode was alive, click here.

Meloidogyne eggs within an egg mass. Those at top and left are
undifferentiated. In the egg at right there's a well-developed juvenile.

There are limits, of course. Many root-knot nematode species will not survive the extreme winters of our northern states. That doesn’t mean that they don’t have nematodes up there. My first plant pathology professor, Dr. Dave MacDonald at the University of Minnesota, told us about a state trooper who found live nematodes after melting dirty snow from a blizzard that had picked up soil from points farther west.

There is so much more that can and should be said about these fascinating creatures. Here are two excellent print resources, used in the preparation of this blog. The third is an online introduction to the topic, from the American Phytopathological Society.

• Shurtleff, M.C., and Averre, C.W. 2000. Diagnosing Plant Diseases Caused by Nematodes. APS Press.
• Sasser, J.N., and Carter, C.C., eds. 1985. Meloidogyne: An Advanced Treatise. NC State University Graphics.
•  Mitkowski, N.A. and G.S. Abawi. 2003. Root-knot nematodes. The Plant Health Instructor. DOI:10.1094/PHI-I-2003-0917-01 Revised 2011  http://www.apsnet.org/edcenter/intropp/lessons/Nematodes/Pages/RootknotNematode.aspx

Note: Many other genera of nematodes are important pests of plant roots, although most don’t cause galls. These tend to live in the shadow of their highly destructive root-knotting cousins, and we’ll give them some attention in a future blog.

Mike Munster and Barbara Shew

The Heartbreak of Botrytis

Decay at the terminal portion of the flowering stem of
poinsettia, due to infection by Botrytis cinerea

Dark blotches are bract
infections by B. cinerea

On Monday, December 16th, we received a sample of poinsettias that for all commercial purposes had been ruined by Botrytis blight. Botrytis cinerea is a pernicious and ubiquitous fungus that particularly infects wounded or senescent tissue such as old flowers. From this foothold it can spread to other plant parts. When the fungus sporulates, the colors of the black conidiophores (spore-bearing threads) and white conidia (spores) combine to give the appearance of a gray mold. The spores are easily carried around on air currents.

Botrytis cinerea can wreak havoc with many different host species, even causing canker on rose canes and fruit rot on plants such as strawberry. More specialized species of Botyrtis also exist. One is Botrytis elliptica, which affects primarily lilies. Botrytis tulipae causes a disease called "fire" on - you guessed it - tulip.

Closeup of conidiophores and conidia of Botrytis cinerea,
growing on cyathia (true flowers) of poinsettia. Black bar = 1mm.

The Achilles heel of Botrytis is its need for abundant moisture. In greenhouses, care must be taken to ventilate, even for a while after sunset, in order to keep the relative humidity down. Watching watering practices (timing, drainage) is also important. Fungicides are sometimes needed. Another essential element in Botrytis management is prompt removal of dead plant material from the house. For more information on Botrytis in greenhouses, see our blog from May 18, 2012.

Pansy bed at NCSU in early 2012. Botrytis blight.

Be on the look out for Botrytis blight on pansies in the landscape, especially in the late winter and early spring. To prevent problems, avoid overhead watering if possible, and make sure the plant spacing and surrounding shrubbery allow for good airflow. For more information on Botrytis in the landscape, see the May 31, 2013 blog.

Light colored dead blotches on flowers, spreading to leaves,
are a hint that you might have Botrytis blight in your pansies.

Just a reminder to check our holiday closing schedule. We look forward to seeing you in 2014!

Mike Munster and Kelly Ivors

Songs of the Season, with a Twist

Are you tired of nonstop carols yet? While not as popular as Santa, plants star in many songs of the season – and some of them have special associations for us here at the PDIC. Number one on the list must be “The Christmas Song,” aka Chestnuts Roasting on an Open Fire. This song reminds us of the blight that devastated the Eastern forests in the last century, leaving us with no chestnuts to roast. “Oh, Christmas Tree” (Oh, Tannenbaum) makes us think of North Carolina’s beautiful Fraser firs and the root rot they must escape before they can end up in our living rooms. Mistletoe figures prominently in “I’ll be Home for Christmas” and holly pops up in “Have a Holly Jolly Christmas” and “The Holly and the Ivy.”

But here’s a song that puts me in the holiday spirit even though the subject and the tune have nothing to do with snow, presents, Santa and all the rest. That’s because for many years, NCSU Plant Pathologists sang it lustily at every gathering, including the annual holiday party. I promise you have never heard it on the radio. Enjoy!

Photo by David Langston, Univ. Georgia

For a nice write up about managing root-knot nematodes, check out this article by Pender County Agent Charlotte Glen.

THE NEMA SONG

(To be sung with gusto to the tune of “The Battle Hymn of the Republic”)

A nematode was chewing on a young tobacco root.

Her keen and piercing stylet was protruding from her snoot.

Her salivary glands were squirting out the poison juice.

The galls keep hanging on.

(Chorus)

We must fight the nasty nema,

We must fight the nasty nema,

We must fight the nasty nema,

Rotate crops and pray.

A cotton plant must suffer on a hot and sunny day.

It transpires too much water when its roots are chewed away.

If we don’t lick the nema we will really have to pay.

The galls keep hanging on.

(Chorus)

Meloidogyne incognita,

Meloidogyne incognita,

Meloidogyne incognita,

Fumigate and pray.

The cortex cells are swelling to a giant size to stay.

The female’s sac’s protruding in a morbid sort of way.

The blind roots now are forming and the root knot’s on the way.

The galls keep hanging on.

(Chorus)

We must fight the nasty nema,

We must fight the nasty nema,

We must fight the nasty nema,

Rotate crops and pray.

Lyrics by Dr. G. B. Lucas

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.

Flies

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.

Ants

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.

Ticks

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).

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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).

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.