In Which I Attempt to Fascinate You with a Minor Plant Pigment

The Amaranthaceae, or Amaranth Family, is a somewhat obscure plant family, but you'd never know it on the farm right now.  There are amaranth crops, escaped amaranth hybrids from last year, and native amaranth weeds taking over the farm this time of summer.  It's a colorful explosion of dramatic bloomers with other meek yet ubiquitous volunteers growing between the rows of actual crops.

The hoop house, a sort of open-sided green house, is bursting with ornamental cock's combs right now.  Cock's combs are in the genus Celosia, and they come in amazing colors: eye-searing red, blazing peach with yellow, glowing whitish-green and orange.  They are such shockingly bright colors due to the fact that they are fluorescent.  Fluorescent colors absorb light energy from outside the visible spectrum (like UV light) and then emit that UV light as visible light...so they do actually glow.  Fluorescence is most noticeable when visible lights are turned off and black lights are shined, but cock's combs are so fluorescent that you notice them in full sunlight.

Hoop house full of Celosias.

A Celosia close-up.  It's even brighter in real life.

Members of the Amaranthaceae and a few other closely-related plant families can fluoresce because they have an unusual class of plant pigments.  Most plants that have red parts use a plant pigment called anthocyanin.  Think maple leaves in the fall and apple skins.  The amaranths use a group of pigments called betalains for all their red and most of their yellow coloration.  Betalains are antioxidants, so they may have anti-cancer properties.  Betalains are also useful as dyes for food and cloth, but I doubt they are what make highlighter pens fluoresce. 

The fluorescence of cock's combs is useful for the plant - it attracts pollinators.  In the hoop house, the peach cock's combs were the hands-down favorite of bees and wasps.  Each plant was swarmed with pollinators large and small.  The peach sector of the hoop house was buzzing, audibly as well as visually, with insect activity.  Good thing I got over my giant ground hornet fear in the previous post. 

Peach Celosia, source.

Amaranths in the U.S. are herbs, though there are some tropical shrubs.  They have tiny flowers, usually clustered all together.  The flower parts are so tiny, they are best seen with a hand lens or dissecting microscope.  Other ornamental amaranths include Gomphrena and Iresine.  Edible amaranth, genus Amaranthus, is used as a grain.  It is an important high-protein cereal native to South America.  Weedy pigweeds, in the same genus as edible amaranth, are found here in the U. S., and though their seeds and leaves are edible, it is much more of a nuisance than a valued crop. 

On the farm, half of our interactions with amaranths involve planting and harvesting the Celosias and Gomphrenas and the other half are killing the pigweeds, spiny amaranths and escapees from last year's crops.  The escaped plants from last year are seeds that have fallen and overwintered in the soil.  They are usually crosses between different types of Celosias, so they have a blend of their parents' traits.  That means they might have unpredictable colors, small flower heads and irregular growth forms.  They don't usually make good cut flowers, and they have to be treated as regular weeds. 

An escaped and hybridized Celosia from last year's crop growing among the zinnias.

And here is your reward (or punishment, depending on your sensibilities) for reading to the end of the post:  Beets are in a closely-related plant family, the Chenopodiaceae, and their red pigment is also a type of betalain.  I have never really noticed fluorescence in beets, but I haven't tried them with a black light.  If you eat a lot of beets, you may have noticed one of the disconcerting properties of betalain.  Betalain is not readily digested by humans, and it either passes straight through the digestive tract or is absorbed into the blood and eventually filtered into the urine.  Either way, the betalains end up in the toilet bowl, the same color as when they were swallowed.

Giant Hornets of Death: Cicada Killer Wasps

For some reason in my Entomology class, my professor really liked to talk about giant ground hornets and how territorial and mad they were.  He told us they would be a trophy to add to our insect collections, but that they were dangerous to catch because their sting was so painful.   Unfortunately, I was afraid of them for years until the owner of the farm on which I work told me that the insect I knew as a giant ground hornet was the same as the cicada killer wasp, which her 9-year-old son loves to follow because of their unique behaviors.

Cicada Killer Wasp, picture source

Well, I had to do some research, and she is absolutely right - they are the same, and cicada killer wasps are generally docile and always awesome.  I actually got to know cicada killer wasps a few years ago because there were dozens of them living in an ivy patch outside the school where I used to work.  We science teachers had to research them to see if they were a danger to the students, and we decided that they were so easy-going that we'd just keep kids from walking through the ivy and that the third graders would study them as part of their Biology unit.  They loved it and no one got stung.  I wish I had connected the dots at that time between cicada killers and giant ground hornets, because I had a close encounter with a giant ground hornet on the farm last week and had a very unnecessary scare.  It would be less confusing if we all just used the scientific name, Sphecius speciosus.

Cicada killer wasps/giant ground hornets are gigantic, up to two inches long.  They are yellow/orangeish and black and variously patterned with usually black abdomens.  They are charismatic animals, and they live large on the landscape.  When they are present, you will see them, but don't be afraid.  The females are technically capable of stinging, but they won't unless they are actually handled.  I'm assuming the ones in the picture below are deceased, either that or they are in the process of stinging.

They're gigantic!  Source

Cicada killer wasps emerge from the ground in early summer.  They feed on flower nectar and search for mates.  After they mate, the females dig a burrow 1-4 feet into the ground, piling up dirt at the entrance to the ground.  The burrows are quite visible in lawns, and many lawn-farmers usually don't appreciate the mini-mole-hills.  They wasps actually prefer bare soil, since it's easier to dig through.  Males cruise around the entrance to the burrow, protecting the burrow from enemies and other males.  Their buzz is definitely bigger than their bite because males can't sting.  Still, they can and do fight fiercely in mid-air, careening around in wrestling-holds with their competitors.

After digging a burrow, the females go on the hunt.  They search for cicadas - but not to eat.  When a female finds a cicada, she stings her prey, paralyzing it but not killing it.  Then the female begins the gargantuan task of hauling the cicada, which can be three times her weight, back into her burrow where she will lay an egg on it and seal it into a chamber.  The egg hatches into a larva which then slowly eats the cicada until the cicada is a shrunken shell and the larva is huge.  Females will make several chambers in each burrow - each of her children gets its own room.  The kiddies overwinter as larvae to emerge next year.

The Wasp Finds a Victim, Source

It seems the female can tell the sex of the eggs she lays.  Her female offspring get two or three cicadas to eat, and her male offspring get just one.  Females grow much larger than males, so they need more food.

Cicada killer wasps have their own parasites that lay their eggs on the cicada killer larvae.  Velvet ants, which are wingless wasps, are parasites on parasites.  If you must fear an insect, you could choose velvet ants (also know as cow-killer ants, though they don't actually kill cows).  Velvet ants have a MAJOR sting, which I can attest to from personal experience.  If you see one, don't bother it!

Velvet Ant Source

A Salad for the Brain

In know, I know, it's not really lettuce season.  Lettuces are cool weather plants that either get tough and bitter or melt into thin papery peels in normal summer weather, let alone in our current stew pot conditions.  Nevertheless, the farm has several warm-season varieties that like our July weather just fine, thank you.

It's composite week on the blog, (see Asteraceae post from yesterday), and I'm continuing on the theme today.  It's always a bit of a shocker that lettuces are in the Asteraceae along with sunflowers, zinnias, daisies and thistles.  They don't even have flowers, right?  Well....actually they are, and they do. 

Garden lettuces all belong to the species Lactuca sativa.  Just like there are many breeds of Canis domesticus (dog), there are many types of lettuce.  Lettuces have the same body plan as all plants: roots, stems, leaves, flowers and fruit/seeds.  The form of lettuce that we usually see is the toddler stage on the full life span of a lettuce plant.  When a lettuce plant grows from a seed, it builds a small root that grows quickly and a few small leaves on a short stem.  The lettuce then proceeds to grow very rapidly, building lots and lots of roots and leaves - but the stem doesn't grow!  All the leaves are clumped together on a short stem low to the ground, forming a head of lettuce.  This stage of plant growth is called a rosette, and many other plants also have this stage, for example, carrots and cabbage.  Here are rosettes of green leaf lettuce, red leaf lettuce and romaine lettuce - all ready to be harvested:

Green leaf lettuce (yes, that's my blue nail polish)

Red leaf lettuce.  Notice the drip irrigation tubes.

 

Romaine lettuce being crowded by crab grass.

Lettuces have categories of growth forms, with many varieties within those categories (like there are many types of labs, which are types of dogs).  The romaines have straight leaves with big ridges.  The butterheads have that soft, buttery texture.   The looseleafs have messy, shaggy heads of leaves.  The icebergs have tight leaves and no actual food value.  The ones I'd like to try are the Chinese lettuces.  They are rumored to taste mild and have stems like asparagus.  I'm going to search for some at the K & S Market.

Lettuce is harvested before it is allowed to finish its life cycle.  I'd call it the veal of the plant world, except lettuce is treated more humanely.  If lettuce were to mature, its stem would elongate and the plant would grow tall like other more normal plants.  The top of the stem would develop into flowers (all ray-type flowers), and then it would produce seeds.  Below are two lettuces I planted in the spring in my home garden, barely watered, ignored then didn't pick.  They elongated and the first one is flowering.  When rosettes elongate, it's called bolting.

A bolting lettuce - quick, catch it!

Another one trying to escape

The scientific name for lettuce is perfect - very informative and descriptive.  Lactuca, the genus, refers to the latex, or milky white juice that is found in the veins of all lettuces.  Next time you eat lettuce, squeeze out some sap - it's whitish.  Sativa, the species part of the scientific name, means edible.  Lactuca sativa: edible plant with milky sap.

That milky sap contains alkaloids, or molecules that taste bitter.  There are more alkaloids in bolting lettuces, so they can be unpleasant to eat.  Other members of the genus Lactuca contain more alkaloids, and some of these are psychoactive.  They can induce a very mild euphoria and lethargy.  Edible lettuce doesn't really have this quality, but because it's a close relative of the other Lactucas, it has been regarded by some cultures as sleep-inducing and has been sometimes served at the end of the night-time meal.  From the plant's perspective, it's making compounds that taste bad to insects or humans, and it protects itself from being eaten.  From our perspective, it's making something potentially useful.  These alkaloids could be isolated and studied for medicinal purposes.

Even the heat-tolerant lettuces on the farm will fade soon.  Lettuce season will be over until later in the summer and early fall when it has hopefully cooled off a bit.

They're altogether compound, the Aster Family

Behold, a giant sunflower, the best-known and most beautiful member of the Asteraceae, or aster family.  The Asteraceae is a huge family with many important members, and it is considered one of the most complex and highly specialized plant families.  The structure of aster-type plants is very different than the basic plant structure, which means it has changed a lot from its evolutionary ancestors.  The Orchid family (Orchidaceae) is also considered highly specialized, and it is an equally large and important plant family. 

Sunflower

The sunflower variety seen here has been bred to produce amazing quantities of  sunflower seeds, but it will serve as my example for how this plant family works.  All members of the Asteraceae have flower heads that are actually clumps of tiny flowers.  If you look closely at the sunflower head above, you will see that is is composed of hundred of tiny yellow and brown structures.  Each of these is a separate flower with its own miniature petals and male and female reproductive structures.  The main flowers in the sunflower are disk-type flowers.  These disk flowers are found in the center of Asteraceae flower heads.  When you look closely at the petals at the edge of the sunflower head, you can follow each one in to see that it is the single petal for a small flower on the edge of the sunflower head.  Flowers with a single large petal are called ray flowers.  Next time you encounter an aster-type flower, tear it apart to observe how it's put together.  You'll easily see how the miniature flowers are clumped together.

Some members of the Asteraceae have only ray flowers, like dandelions and chicory.  Others have only disk flowers, like thistle and ageratum.  Most composits, as members of the Asteraceae are also called, have both disk and ray flowers, like daisies, rudbeckias and zinnias.  Often ray flowers are infertile, meaning they don't actually produce seeds.  On the sunflower above, the disk flowers will each mature into sunflower seeds, but the ray flowers will just fall off.  Their job is finished after they have attracted bees to the newly-opened flower head.  Disk flowers are inconspicuous and do not attract bees very well, even though they produce seeds.

In zinnias, the ray flowers mature first, which you can see in the picture below.  You might just call the ray flowers petals, if you didn't already know better.  Disk flowers mature as the flowers age.  They look like yellow mini-flowers in the center of the main flower. 

Zinnia

Below is a row of rudbeckias, also known as Mexican hat flowers.  Rudbeckias, like most aster-type flowers are great at attracting pollinators like bees, butterflies and other insects.  The pollinators they attract also pollinate other plants nearby, like the tomatoes in the next row.  Many of the pollinators are also predatory insects that help to eat harmful insects.  These flowers are an important farm crop, but they also help keep the farm working smoothly and make it look gorgeous.

Rudbeckia

 I couldn't resist including this last picture.  I spent my first hour on the farm today harvesting zinnias and sunflowers, my two favorite flowers.  It was a special delight to walk among the 7-foot-tall sunflowers as they faced the morning sun.  The bees were just getting started working for the day, and their buzzing grew louder by the minute.  By the time I was finishing, I had to wave bees off of the flowers as I cut them down.  They were surprisingly patient with me, just moving on as their flowers fell beneath them.  As I finished the task, I carried away sunflowers by the armful for some very lucky farm customers.

Sunflowers facing the sun

In a Pickle

I was out of town last week, and I came home to cucumber vines loaded with over-sized cukes.  I picked every little baby cucumber before I left, and still they exploded with fruit in five days.  There was nothing to do but pickle them. 

Kirby Cucumber

I have always pickled my cucumbers by adding vinegar, salt and spices and then processing the jars in a water bath to sterilize the pickles.  Since pickles are acidic (from the vinegar), it's easy to home-can them without a pressure cooker, as they don't need to be heated above boiling.  I always use Kirby cukes, since they are crisper.  They have tiny spines on them, but I just rub them off with my hands, cut off the ends and cut the cukes into long spears.  I remove the seed core as I cut - it just makes better pickles that way.

This year, I had no time to home-can when the cukes were ready.  My cucumbers had to do the work themselves.  I found a recipe for fermented Kosher cukes, and went to town.  Home-fermented cukes don't use vinegar - they make it!  There are bacteria and yeast naturally found on the cucumbers, the spices, the dill, and if you give those little critters the right conditions, they will turn cucumbers into great pickles.  Here is a jar of cucumbers in the process of becoming pickles.  You can see the dill and spices I added.

New pickles plus dill, coriander, mustard seeds, pepper, garlic and more.

Here's how fermentation works.  There is an enormous variety of bacteria, yeast and fungi on every surface around you, including you.  Those microbes are all either actively eating whatever they are growing on, or they are waiting come into contact with something that is food.  Microbes use food resources in a variety of ways, all producing energy, but usually producing interesting byproducts too. The process of microbes breaking down food (usually without oxygen) and producing byproducts is called fermentation.  Some microbes break down perfectly good produce for food, leaving behind bubbles of carbon dioxide and a watery mess.  Incidentally, this is also what we produce when we break down food for energy!  When you see a rotten spot on a tomato, you know one variety of microbe has won a battle and is taking over.  When oxygen is absent, other bacteria can break down the produce and leave behind methane or botulism toxin.  Others produce a variety of acids, and these are the ones we're using for pickling. 

Acid-producing bacteria grow well with a limited amount of oxygen, and many of them are salt-tolerant.  Most disease-causing bacteria are not salt-tolerant.  If you give them a food source, such as a fresh cucumber, and eliminate competing microbes by keeping out most oxygen and adding salt, the little acid bacteria can go nuts.  They break down the sugars in the cucumber and release lactic acid and acetic acid, which tastes sour and helps keep even more harmful bacteria out of the food.  It is not a coincidence that vinegar is acetic acid.  In fact, vinegar is produced by a similar process as my home pickles, but using apple cider, wine or some other food source for the bacteria. Other sour-tasting foods are produced by a similar process, for example yogurt and kim-chee. 

Once a food has been fermented, the acid adds extra protection against spoilage by non-desirable microbes.  Before refrigeration and easy inter-continental transportation, pickling food was a major way of having food in the winter.  All kinds of things can be pickled: green beans, okra, hot peppers, eggs (they're good!), carrots, garlic and more.

After two days, my cucumbers are pickling away.  There is a little foam on the top of the pickle jars, and the liquid is becoming predictably cloudy.  I'm going to taste them each day, provided they look and smell like I expect them to, and when they are sour enough to my taste, I'll seal the jars and refrigerate them.  They should theoretically keep a long time if we don't eat them, and I could can them to make them last even longer.  Since canning involves heating them in boiling water to the point of sterilization (about 20 minutes, depending), the cucumbers will be less crunchy. 

Active fermentation going on here.

A little reassurance for the germ-phobes out there:  the microbes that live on you are mostly helpful.  They compete with disease organisms, they help digest your food, and they help keep your immune system working well.  A good variety of microbes is a great asset to your health.  If you add everything up, our bodies contain way more non-human cells than they do human cells.  The microbes in fermented pickles are good for you.  Yes, a stray bacterium can get into the batch and spoil things, so you have to watch out for contamination.  Remember, if it looks like a pickle and it smells like a pickle, it is probably a pickle.

Nightshades: Deadly and Delicious

This week on the farm, I harvested tomatoes, specifically orange cherry tomatoes.  We are just tipping over the edge of the top of the tomato waterfall on the farm.  Soon we'll be picking bucket after delicious bucket in a rush to keep up.

The orange cherry tomato fruits look remarkably like the fruits of one of our most poisonous local weeds, the horse nettle.  I can attest, from eating several tomatoes as I harvested, that the cherry tomatoes are delicious and non-toxic.  Here are pictures of both fruits:

Orange Cherry Tomatoes, picture source.

Horse Nettle Berries, picture source.

These two plants are actually close relatives on the evolutionary tree.  They are both in the plant family called the Nightshades, or more scientifically, the Solanaceae.  They don't belong to the same genus, (Lycopersicon esculentum for tomatoes, and Solanum carolinense for the horse nettle), but they have a surprising number of traits in common.  All members of the Solanaceae have flowers with 4-5 petals, alternate leaves, radially symmetrical flowers, and fruits that are technically berries or capsules. Both of our featured plants today have flowers with 5 petals that radiate our like little stars.  Tomato flower petals are usually yellow, whereas horse nettle flowers are light purple, but otherwise the flowers are nearly identical.  They both have fruits that are berries, meaning they are produced from one ovary and have a fleshy interior.  (As you might suspect, the botanical term berry is different than the grocery store term.  Strawberries and raspberries are not berries, watermelons and bananas are.  Don't worry about it.)  Cherry tomato and horse nettle berries are virtually identical inside and out, at least upon visual inspection.  Our two plants also have similar leaves and similar overall growth forms.

Tomato flowers, source.

Horse nettle flowers, source.

These two plants reenact the history of the Solanaceae as it affects humans - the question of whether a nightshade will nourish or kill.  The Solanaceae has no doubt been responsible for many of both outcomes.  It is a major plant family, with many species of major importance to humans.  The list of nourishing nightshades is impressive: tomatoes, garden peppers and hot peppers, potatoes, eggplants, tomatillo and more.  The poisonous nightshades include tobacco, potato (the greed parts), Jimson weed, belladonna (also called deadly nightshade), and mandrake. 

Considerable prejudice against the Solanaceae built up in Europe, as most native nightshades are highly toxic.  Our edible nightshades originated mostly in the New World.  As tempting as it is to think of tomatoes as Italian and potatoes as Irish, these plants were imports to Europe after they were 'discovered' by European explorers.  At first, Europeans were hesitant to eat the imported nightshades, but soon they incorporated them seamlessly into their cuisine.  Remnants of nightshade phobia exist today, with some people avoiding them altogether.  It is possible to be allergic to nightshades, which makes navigation of modern American cuisine very difficult - no French fries, no tomatoes, no hot sauce!

Toxic nightshades have a rainbow of alkaloids.  Mandrakes and Jimson weed are grimly hallucinogenic in smaller doses and toxic in larger doses.  Tobacco is addictive and stimulant, and the number one killer in the United States.  Belladonna is likely the most acutely toxic plant of the Western Hemisphere, with only a few of the sweet-tasting berries necessary to kill a person.  It has been used to make poison-tipped arrows.  The alkaloids in these poisonous plants can be useful to medicine.  For example, atropine, discovered in belladonna, is used to make the substance that dilates eyes in eye exams, to speed up the heart, and to counteract some pesticide poisonings.   

Birds Do It, Bees Do It........Even Zucchinis Do It

I am the only person in the world who seems to have trouble growing zucchini.  They are notoriously generous in fruit, and you always here gardeners joke about being overwhelmed by their zucchini crops. There are even stories about gardeners secretly dropping of baskets of zucchinis at their neighbors' houses just to get rid of them.

I've gotten better at growing zucchini plants through the years, but still have little luck with the actual fruits.  (Yes, they're fruits, according to the botanical definition.  Any plant part that contains seeds is a fruit.  Don't worry - I call them vegetables when I'm cooking.)  My home garden has a lot of shade for a garden, and my first few years of planting zucchini in the shadier regions allowed the plants to be overcome by a dusty white mildew.  Any zucchinis would wither and rot before they grew two inches.  Now my plant is in the sunniest patch I have, and it's healthy, but my zucchinis are still withering prematurely.  Here is this year's zucchini plant, recovered from the hail damage:

After talking with the farm owner where I'm working this summer, we agreed it might be a pollination problem.  Pollination is how plants reproduce, and seeds and fruits are the offspring of plant reproduction.  Pollen, is the plant equivalent of sperm, and it must reach the botanical equivalent of eggs, called ovules, for seeds and fruits to develop.  There seem to be two possible pollination problems in my case:  maybe there aren't enough bees to pollinate the flowers; or maybe there must be two plants for successful pollination.

Option 1, not having enough bees, is a distinct possibility.  There aren't many bees in my neighborhood.  I do see bumble bees, but they tend to cluster out front where all my ornamental flowers are.  I have seen no honey bees this year, which I fear is due to colony collapse disorder - see a future post on this.  To remedy this problem, I could plant some bee-attracting plants near my zucchinis so there is more of a reason for the bees to fly all the way over there.  I could also start a honeybee hive in my back yard, which I will do some day if my neighbors aren't reading this blog.  Or, I could hand-pollinate the flowers when they open every morning, which is what I have been trying.

To hand-pollinate the flowers, you must understand a little about the reproductive organs of zucchini plants.  Flowers are always reproductive organs for plants, but each type of plant is a little different.  Zucchinis and all squash-type plants produce separate male and female flowers.  Most types of plants have male and female in the same flower, but some may have entirely separate male plants with only male flowers and also female plants.  Hollies have separate genders, which is why only some hollies grow berries - only females can grow fruits and only males can produce pollen.

On zucchinis, the female flowers grow out of what looks like tiny immature zucchinis.  This organ is the female flower's ovary, and it is filled with ovules.  The ovary will one day actually become a zucchini, and the ovules will become seeds after the flower is pollinated.  Notice the thick regions behind the female flowers below - they are ovaries.

Male flowers have a normal stalk, and inside the male flowers are pollen-producing organs called anthers.  Here is a male flower:

For pollination to occur, the pollen must be transferred to sticky pads, called stigmas, inside the female flower.  Each pollen grain then produces two actual sperm cells that burrow down through the flower to an ovule and fertilize it.  Many pollen grains are needed to fertilize all those ovules inside a zucchini ovary.  When the ovules are fertilized, the fruit begins to enlarge and grow into a mature zucchini with mature seeds.  If no pollen is transferred, or only a little is transferred, there is no signal to the plant to grow the fruit, and the ovary just withers and rots like mine have been doing. 

I have been hand-pollinating for a couple of days now, by touching my finger to the anthers in the male flowers and smearing the pollen on the female flowers.  I think it may have worked!  Here you see the stigmas inside of a female flower and what I think may grow into an actual zucchini:

Regarding the second possible pollination problem, I may have to plant two zucchini plants next year.  Since I only have one zucchini plant, the pollen I used came from the same parent plant as the flower I transferred it to.  Some plants don't mind reproducing with themselves, but zucchinis may be somewhat pickier.  The zucchini that seems to be growing could have been pollinated by pollen from a neighbors plant.

On the farm, the year they had a bee hive, the squashes were much more productive, since all their flowers were being pollinated.  It really makes you appreciate the bees more when they are not there to do that garden task for us. 

The Ladybug's Obnoxious Cousin

Everyone loved ladybugs as a child.  We picked them up; we counted their spots, and we may have even brought them inside.  The cute, round bugs are ubiquitous on children's books and clothes.  Ladybugs are some of our earliest friends, so it's surprising to find a pest dressed up like our little pals.

The Mexican bean beetle looks like a ladybug that has rolled in the dust.  It's coppery-brown but still covered in spots and half-dome-shaped.  These beetles are true ladybugs, and they are classified in the ladybug family, the Coccinellidae, which is a subset of the beetle order, the Coleoptera.  All my entomologist readers just cringed a bit after reading that last sentence (sorry!), since ladybugs are not actually bugs.  Entolomogists call them ladybird beetles.  I still use the term ladybug, because that's what I learned when I was 4 years old.  True bugs are in a different group of insects, Order Hemiptera, that includes stink bugs, aphids, leafhoppers and cicadas, but definitely not beetles.

Unlike almost all the other types of ladybugs, Mexican bean beetles are damaging to crops.  Ladybugs are generally famous for their ability to eat vast quantities of aphids and other pest insects.  But Mexican bean beetles are infamous for their herbivorous appetites.  The adult beetles are only moderate consumers of bean leaves, but after they lay their eggs, the larvae which emerge are voracious and insatiable.  Right now the larvae are out in full force.  Their little spiky orange bodies look like tiny Pokemon characters covering the bottoms of the leaves.  Every few days, as they grow, they slip out of their skin and leave it behind to grow a new one.  After a few weeks, they shed their skin and emerge as adult beetles.  Here is a spiky Mexican beetle larva along with some major leaf damage:

The Mexican bean beetle is currently helping itself to the snap beans on the farm, and it seems to show a slight preference for one of the two varieties we have.  They technically will eat any kind of bean plant, but snap beans and lima beans are their favorites.  Many of this season's bean plants have been reduced to lacy brown ghosts of themselves.  The plants are still are squeezing out a few green beans, but these poor plants are stressed to the max by their little inhabitants.

There are many strategies to dealing with Mexican bean beetles on an organic farm.  One strategy is to time the bean crops to minimize damage.  The beetles emerge every year around mid June.  They have overwintered as adults, hiding in warmer places or under debris, and the first adults to emerge are especially drawn to bean plants to lay eggs.  If you plant your bean crop early, you can harvest beans before the scourge begins.  Also, you can wait until the first round of adults emerges and flies somewhere else to look for beans and then plant your crop.  It is thought that eliminating probable overwintering locations can be helpful.  Beans in infested areas should be harvested quickly before the beetles can damage them. In addition, the larvae are susceptible to insecticidal soaps, which disrupts their cuticles and they desiccate. 

The farmer I work for is using a neat but gruesome approach to eliminating the Mexican bean beetles.  She and her son ordered wasps through the mail and released them into the bean field.  These wasps lay their eggs on Mexican bean beetle larvae.  The wasp eggs grow inside the larvae, eating its flesh, and then they emerge from the larvae as adult wasps that go on to lay their eggs on other unsuspecting beetle larvae.  As you might suspect, the larvae do not survive this process!  The parasitized larvae enlarge and turn orange-ish.  At this stage, they are referred to as mummies.  Here is a picture of a bean leaf with both yellow larvae and orange mummies:

The wasps' life cycles repeat in quick succession, and soon the larvae should be mostly mummified.  The bean plants will hopefully recover - even now, their newer growth looks healthy and robust.  Soon I'll be able to stop looking at every ladybug with a suspicious eye.

Here is your reward for making it to the end of this post:  All members of the ladybug family can secrete a noxious compound from their knee joints when they are irritated.  The compound is subtle to our noses, but you can smell it if you bother a ladybug and sniff its knees.  The scent from Mexican bean beetles is a little stronger.  This secretion is a deterrent to predators, who find it distasteful.