Zombie Worms From Planet Sphinx

This time of year, when you're harvesting tomatoes, you often notice part of the plant where the leaves seem to be missing and all that's left are stubby stems.  This is not a deformed tomato plant.  Look closely and you will see a stem that seems to be especially thick and stubby like so: 

Tobacco Horn Worm (Source)

The gigantic worm above is a tobacco horn worm.  It is a positively ravenous caterpillar that literally stuffs itself with tomato or tobacco leaves.  If you touch one, it seems to be so full that its skin feels like a grape leaf around a dolma.  It eats so much of the tomato plant that it can reduce tomato productivity dramatically.  Farmers dislike these caterpillars, but I bet most of them also admire the strangeness of these creatures. 

Tobacco horn worms grow from tiny eggs deposited on tomato plants by the Carolina sphinx moth, a gorgeous night creature that moves and hovers like a hummingbird.  It has a coiled proboscis that it uses to probe nectar from night-blooming flowers trumpet-shaped flowers.  Here is a sphinx moth feeding on an azalea:

Sphinx moth feeding.  (Source)

 Sometimes when you see a tobacco horn worm, it will appear to be covered with dozens of white, ovoid bead-like objects.  When you see this, you know the horn worm is one of the walking dead.  The white things are the pupal cases of a type of braconid wasp, which lays its eggs under the skin of the horn worm.  The eggs hatch inside the horn worm and eat the worm from the inside out.  The larvae begin to burst out of their horn worm and weave little white cases with lids around themselves.  In a few days, they will emerge as adult wasps, and the horn worm will expire as a shrunken husk of itself.  The adult wasps will go on to infect and kill other horn worms.  Braconid wasps are friends of the farmer because they help do the work of dispensing with horn worms.  Anytime a farmer sees an infected horn worm, she lets it be so that more wasps will hatch.  Farmers can even order braconid wasps in the mail to release on their farms.  Here is an infected horn worm:

I know it's hard to see, but there is a parasitised tobacco horn worm in the middle of the picture.  I'll bring a better camera to work tomorrow.

 Here are some better pictures I didn't take from this website:

A good picture of an infected hornworm.

An adult braconid wasp spreading its wings for the first time.

Caught in a Web of Suberin

It's melon season.  We're searching through the melon fields to collect the ripe ones on the farm right now.  Testing for ripeness is an art, and it varies for each type of melon.  The cantaloupes are perfectly ripe when the stem easily peels off the top of the fruit.  We farmers refer to this as 'full slip', as in, "That melon's ready to go - it's full slip."  The reason melons from our farm (and, to be fair, other local farms) taste infinitely superior to supermarket melons is that mass-market melons are harvested at half-slip or even earlier, so the fruit flesh doesn't mature into as complicated of a combination of sweet and aromatic notes.  In addition, supermarket melons are treated with a compound to prevent their rinds from molding.  Unfortunately this treatment also prevents the melons from smelling like melons.  Go buy a melon from the farmer's market or your local organic farmer (my favorite is here: Fresh Harvest Cooperative).  Even if you hated canteloupe as a kid, like I did, you will not be able to stop eating a delicious local ripe cantelouple. 

The farm I'm working on grows a variety of melons.  Here is what I harvested one day this week:

Genetic diversity in melons on our farm.

The picture above contains two varieties of watermelons, cantaloupes, an heirloom variety of cantaloupes, and honeydews.  All the types of melons above except the watermelons are types of muskmelons.  Muskmelons are tropical melons originating from Africa or the Near East.  They require a long warm growing season.  They are in the same plant family (Cucurbitaceae) as squash and cucumbers, so they have to deal with squash bugs, too. 

Have you ever noticed the netting on the rind of cantaloupes?  If not, take a look at the cantaloupe below.  If you did notice the netting, did you ever wonder what it was doing there?  Not me, but when I started reading about cantaloupes for this post, I found out the most fascinating thing about that netting.

Netting on cantaloupe rind.

The netting on cantaloupe rind is made of a substance called suberin.  Suberin is a fantastic molecule produced by many plants.  It is waxy and waterproof.  On the cantaloupe rind, anywhere the rind cracks as it grows, the cracks are quickly filled in with suberin.  The suberin helps keep the juiciness in and the moldiness out.  It's basically very much like a scab on our skin, but not gross.  Fortunately for me, but not for the farm owner, suberin fails on occasion and a crack becomes too large to grow a suberin scab.  These cracked melons cannot be sold, but they are fine to eat as long as they don't get moldy and aren't inhabited by an ant colony.   I've been stuffing myself with melon culls for two weeks now.

But back to suberins.  You may already know suberins from their most famous location.  Cork is pretty much solid suberin.  Cork is the almost-outmost layer of bark of the cork oak (Quercus suber).  It provides waterproofing for the cork oak, enabling the cork oak to survive in the very dry areas around the Mediterranean Sea.  It provides the same function when humans peel it from those trees, cut it into cylinders and cram it into wine bottles. 

You will probably be surprised to learn that roots of almost all plants contain microscopic layers of suberin under their surfaces.   This seems ludicrous at first, since roots are supposed to absorb water. You'd think the last thing a plant would want is a layer of waterproofing around their roots.  In roots, suberin helps the plant regulate what can get into the plant.  There are doors and windows in the suberin layer, and those openings let in water plus the minerals the plant needs.  The openings keep out anything the plant doesn't need, such as too much salt, harmful bacteria or lots of other things that could be dissolved in groundwater.  Mangrove roots are highly suberized to keep out the salt of the ocean water in which they grow.

 Suberins are actually a group of complicated molecules.  All suberins have a similar structure, but they can vary slightly in their components.  Suberins are long polymers of smaller molecules, arranged variously but allowing crosslinks.  These molecules have a lot in common with oils, which makes them hydrophobic and water-repellent.  A little-known fact about suberins is that they have their own facebook page. 

Many varieties of melons don't have suberin netting, including most honeydew melons.  Their rind is smooth and net-free. The lack of suberin is not due to an inability to make suberin or an absence of the gene for suberin.  In melons lacking netting do not express the gene for suberin in their rinds.  The difference between netted and non-netted melons is a genetic difference, but not in what the DNA says.  The difference is in how the DNA is read.  Imagine the DNA for melons as a book.  If you read the pages in a different order, you get a different story.  For honeydews, the suberin chapter is skipped over altogether, except in the root cells.  (Source)  I don't know why honeydew melons don't have cracks on them.  Their rind must be able to expand around the fruit without cracking. 

I'll leave you with this picture of last week's melon harvest. 

Nice melons!  Ready for the market.

Squishing the Squash Bugs

See those dots?  They're the little bronze balls at the center of the squash leaf in the picture below.  These are newly-deposited eggs of the gross squash bug. 

Squash bug eggs

 Squash bugs are attacking the zephyr squashes on the farm.  Zephyr squashes are green and yellow zucchini-like squashes.  They are very generous plants, and we have to collect them every two days while they are in season, or we'd be buried in giant squashes.

Yellow squash, zephyr variety

 Squash bugs belong to the insect order Hemiptera.  Stink bugs, aphids, cicadas and assassin bugs are also Hemipterans.  Hemipterans have piercing, sucking mouth parts (think sharp straws), only one pair of wings, and commonly have a shield-shaped patch on their backs.  They usually eat like kids consume drink boxes:  poke in the proboscis and suck out the liquid.  Most Hemipterans eat plant sap, but a few (like assassin bugs and toe-biters) specialize on blood or insect juices.  Technically, Hemipterans are the only bugs that can be called bugs.  They are the "true bugs" of the insect world.  All other bugs are just insects.

Squash bugs drink squash juice, which can be found inside squash plant leaves, stems and fruits.  They are voracious, and they can suck out so much squash sap that the leaves can wilt and smaller plants can just wither and die.  More commonly, they damage plants by walking through diseased portions of the plants and treading spores to other parts of the plant.  They also make little specks on zucchinis, acorn squash and other squashes, which reduces their retail value if not their food value.  In addition, they creep out their squash farmers.

Yes, there is a squash bug in the center of the picture

 Adult squash bugs are shy.  If you try to take a picture of one, they will constantly walk to the opposite side of the stem from where you are.  That is why the picture above is so lame.  They also congregate under dead leaves or other things on the ground.  One way to catch a lot of squash bugs is to set a board on the ground under an infested plant.  Then go back the next day and squish them all.  Or brush them into soapy water if you don't like squishing bugs.

Younger squash bugs are easier to find.  After they hatch, they hang out under squash leaves and gradually spread out over a few days.  I was 'lucky' enough to find this cluster of squash bug nymphs and get a picture before they scattered.  They are slower than adults, so they scatter slowly.  If you find a bunch of squash bug nymphs, you can brush them onto the ground and stomp them, or brush them into soapy water.

A billion little squash bug nymphs.

On the farm, we kill squash bugs if it doesn't slow us down from the rest of our work.  We also squish the eggs when we can.  Mostly we use timing to reduce the impact of the squash bugs.  Squash grow quickly, but squash bugs take almost a month to hatch and grow to fighting size.  By that time, the squash bugs are really cooking, the squash plants have been fruiting for a week or two.  Also, squashes grow so quickly, most of the squashes escape damage and can still be harvested.

Abundance

It's been a wonderful year for produce.  Every crop seems to be generous this year, except the poor green beans that were infested with Mexican bean beetles.  The tomatoes are exploding (figuratively, as well as literally, since some are rotting on the vine).  The flowers are lush and bright.  The squash are growing so fast it's hard to keep up with them.  We've had good weather and adequate water, and the plants are doing exactly what they do best.

Most of a bushel of tomatoes before they were turned into sauce.

Abundance brings the exquisite dilemma of what to do with too much food.  I've accepted the challenge of helping to preserve the amazing overflow of tomatoes we have in Middle Tennessee this year.  We've been eating all the extra tomatoes I get from the farm, mostly as tomato peach salad, which is the single most delicious food item I have ever experienced (thanks to the farm owner for this idea!).  I also rescued about a gallon of split sungold cherry tomatoes last week and dried them in my food dehydrator, resulting in hundreds of little sweet/tart tomato bombs for my salads and pizzas.

The best use of the tomato abundance has been my tomato sauce.  For this, I bought tomatoes from the farmer's market, as we don't have quite enough rescues from the farm to make all the sauce I want.  I've processed and canned bushels of tomatoes, and I have it down to a fairly streamlined and straightforward process.  Still, you'll need about 2.5-3 hours from start to go from tomatoes to sterile jars of sauce.

A pint of liquid summer.

Here's how to do it:

1. Wash your jars in the dishwasher, with hot water.  Right before using them, dip brand new lids and any old (or new) bands in almost boiling water to reduce bacteria.  Lids can't be reused!
2. Make the sauce (see below) and keep it hot.
3. Add 1/4 teaspoon of citric acid to each pint jar or  1/2 teaspoon to each quart jar.  This reduces acidity in the jars so they are less likely to spoil.
4. Boil water in a giant pot.  Boil enough that the water will be 1" over the tops of the jars after you put them in.  This is a little tricky the first time, but you'll get the hang of it.  You can always boil a little more in the microwave and add it to the pot if you don't boil enough.
5. Fill jars leaving 1/2" of space at the top of the jar, wipe off any mess at the tops of the jars, and close the lids on them just to finger tight.
6. Immerse the sealed jars in boiling water (covered by 1" of water) for 35 minutes for pints and 40 minutes for quarts.  Start timing when the water returns to a boil after adding the jars to the water.
7. Set the jars on a counter over night to cool without disturbing them.  They make cute little pinging noises as they cool.
8. Write the date on the lid (it can't be used again, so just go ahead and write it), and put it in the cabinet for later. 
9. This sauce works great on pizzas, pastas, lasagnas, eggplant parmesan or anything of that sort.

Now for the recipe.......

Since you're using citric acid, there's a little leeway on proportions of ingredients, but you don't want to use much besides tomatoes.  Tomatoes are acidic, and acid helps preserve the sauce, so you don't want to dilute the acid too much.  Just multiply the ingredients to match the amount of tomatoes you have.  I actually usually use more tomatoes than the recipe calls for - it's flexible as long as you don't use less tomatoes.

Tomato Sauce
2 T olive oil
1/2 onion
1 small carrot, diced
1 stalk celery, diced
2 T fresh parsley
1 clove garlic, pressed
2 T fresh basil
12 medium tomatoes
1 t tomato paste
salt and pepper

1. Wash the tomatoes, and only use the ones in good shape.  Cut out the stem area and slice the tomatoes in half across the middle horizontally.  Squeeze out the liquid and many of the seeds by squeezing each half of the tomatoes.  Save hours by not peeling them.  It's totally not necessary, dude.
2. Heat the olive oil in a big pot, and add the onion, carrot, celery and parsley.  Saute a bit, then cover and heat on low for 15-20 minutes, stirring from time to time.
3. Add the garlic and increase heat to medium.  Add the tomatoes, tomato paste, basil, salt and pepper, and heat to boiling.  Use scissors to chop up the tomatoes into smaller chunks - right in the pot!  This is really fun.
4. Simmer uncovered until thick.  Use an immersion blender to make the sauce fairly smooth.  Can the sauce while it's still boiling according to the directions above.


It's a very straightforward process, and this is a great one to try for new or experienced canners.  If you follow my instructions exactly, it's hard to go wrong.  If you deviate from the instructions, it is important that you take precautions because improperly canned food can be deadly.  You have two options:  (1) freeze the sauce, or (2) do more research on the Internet to see if your deviations from canning protocol are acceptable.  I encourage you to try it - you'll be really glad to have the taste of real tomatoes in January.

Not All That Buzzes is Black and Gold

The airspace on the farm is busy.  There is no air traffic control, but no one seems to collide.  I'm a giant lumbering along amongst the cloud of busy insects as I work my way down rows of flowers and vegetables.  They hardly seem to notice me as they go about their work.  With so much time and so many insects, I've gotten to know their sounds well.  You can tell an amazing number of buzzing insects by the qualities of their buzzes.

The easiest to recognize are the cicada killer wasps I wrote about a few weeks ago (here).  They have a steady bass tone - a low buzz in which you can occasionally hear individual wing beats.  They are loud and their pitch only changes from the Doppler Effect, lowering a bit as they fly away.

Cicada killer wasp.  Picture source.

Bumblebees are the most common on rows of flowers.  Their buzzing is all fits and starts as they whiz from one flower to the next.  They seem to have trouble steering because they swerve around a flower's entrance before crawling onto it, so their pitch varies widely as they try to align themselves for landing. They are generally loud and low in pitch.

Bumblebee.  Picture source.

Honeybees are quiet and unfortunately rare on the farm.  They move and sound a lot like quiet, higher-pitched bumblebees.  If bumblebees are the bases, honeybees are the tenors.  Sweat bees are the sopranos.  They have these little tiny, quiet buzzes as they try to wedge themselves into the backs of your knees so they can sting you when you squat down.  They are usually unnervingly near you, and they whiz off when you try to swat them.

Sweat bee.  Picture source.

The bugs, stink bugs and assassin bugs, are hilarious once you get used to them.  They buzz so stereotypically that I expect them to have little captions over their heads filled with z's.   They hide amongst the green parts of plants instead of the flowers, and they wait until the last minute to try to escape from a perceived threat.  I'll be harvesting tomatoes and all of a sudden a loud buzzing bug will be flying erratically very near by.  No other buzzing insect buzzes so close and loud. 

 

 

 

Leaf footed bug.  Picture source.

There are some stealth insects too.  Wasps usually don't make a sound.  If you are very quiet, you can hear a little purring noise when they are very close, but usually they just seem to float by noiselessly.

Paper wasp.  Picture source.

Tomato Hands

The strangest thing happens when you harvest tomatoes for hours:

Tomato hands!

That black stuff is called tomato tar, and it builds up on your hands as you handle the green parts of tomato plants.  It's thick and a little sticky, and some patches where it's especially thick have a greenish hue.  When you try to wash your hands, it turns the water yellow!  It also takes about 5 serious washes to get it off of your hands.

Matt's Wild variety of cherry tomato, and some tomato-y hands.

It turns out that tomato tar is the same wonderful compound that makes a tomato plant smell like a tomato plant.  It is an oily secretion produced by hair-like structures called trichomes.  Here are some trichomes sticking out of the rachis (stem) of this tomato leaf:

Trichomes and proof that my hands eventually got clean.

Under a scanning electron microscope, you can see that about half of tomato trichomes have a swollen structure filled with a yellowish secretion.  This link connects to an image taken by a molecular biologist named Anthony Shilmiller whose entire career is studying tomato trichomes.  In fact, he's part of a team of scientists who study tomato trichomes!  The Solanum Trichome Project studies the structure, genetics and chemistry of tomato trichomes, and they can be found here.

Now before you call your congressman about how much money is wasted on paying multiple scientists to study tomato hairs, please read a little further.  Glandular trichomes of tomatoes can produce a variety of substances, depending on the genetics of the plant.  Those substances can influence flavor, deter insects, prevent plant disease, and smell incredible (or terrible, as the case may be).  Since the total value of the 1997 US tomato crop was $1,246,843,000,(source), and the value of tomato crops depends on flavor, insects and disease, you start to get a sense of the value in being able to use tomato trichomes to one's advantage.


Most plants have trichomes.  Aromatic herbs like mint often produce their wonderful-smelling oils in glandular trichomes.  Trichomes can also be hair shaped without a gland.  These can help leaves shed or retain water or deter insects.  Trichome shapes can vary widely.  In fact, as a last resort, many leaves can be identified by their trichomes.


Tomato trichomes have another use that we can take advantage of.  If you place a leaf or three in broth or stew or anything you want to taste like tomato, you can enjoy a very intense tomato flavor.  Just add the leaf as you simmer and remove it before you eat - like a bay leaf.  The trichomes burst and release their oils into your broth as it simmers. 

A Time to Sow

Seasons are changing already on the farm.  Crops are maturing, exhausting themselves and giving way to insects, and it's time to plow them under and start anew.  The chard, beets, onions and lettuce were past the point of diminishing returns, so last week we demolished them and and set up twelve new beds, which are already starting to grow.  We'll soon have new chard, beans, lettuce, beets, turnips and carrots.

To change over the beds, we remove the irrigation system (see below), and the farm owner plows the crops under.  Then I spread organic fertilizer on the row, and the farm owner plows again.  Maybe after a few more years I'll get to learn how to drive the tractor, but for now, I stick to raking the biggest of the dirt clods and weeds out after the plow goes through.  The beds are perfect at this point - fluffy, weed-free and ready to be planted.

There are two ways we plant new beds:  one is transplanting seedlings into the soil that have been started in the greenhouse, and the other method is directly planting seeds into the soil.  The method of planting depends on the type of plant.  Those with a long taproot, like carrots or beets must be direct-sowed, and others like squash or kale or most flowers can be started in the greenhouse and transplanted.  I started hundreds of seeds in the last few weeks for transplanting, but we won't get to those until next week.  Last week we were direct-sowing. 

There is an ingenious little machine on the farm for direct-sowing.  It's called the Earth Way Precision Walk-Behind Garden Seeder.  Here is a picture of the whole machine and of the seed chamber filled with chard seeds:

The front wheel has a groove for making a seed furrow.  The wheel inside the chamber scoops 1-2 seeds at a time, and you can easily replace the wheel with a different-sized chamber for different seeds.  The seeds fall down a chute into the furrow in the soil.  There is a chain dragging behind the chute for pulling the soil back in place.  The back wheel is flat for pressing the soil down over the seeds.  Genius!  It worked very well, too, except for the carrot seeds, which had a coating on them for supposedly making them easier to sow evenly. 

We usually make 4 rows per bed.  Since this was my first time seeding, the rows were a little wonky.  I know they'll look a little strange as they start to sprout, but we won't notice the crookedness once the plants get big.

After we seed, we lay irrigation tape over the rows of seeds.  It has holes every twelve inches to drip water directly onto the soil.  Drip tape distributes water very efficiently, and it wastes much less than sprinklers.  The irrigation tape can be reused many times, though I learned the hard way that wound-up balls of used drip tape make great places for wasps to nest!  Fortunately, I wasn't stung, but many poor wasps lost their home. 

Direct-sowing is quick and easy compared to transplanting, but there are some trade-offs.  First of all, the seeds are often planted too close together, and then they must be thinned.  Also, sometimes the direct-seeder malfunctions and entire swaths of the rows don't get planted, which you don't notice until the seeds sprout.  When growing seeds for transplanting, every seed usually germinates.  Expensive seeds aren't wasted, and every bit of the bed ends up with actual plants growing on it.

I seeded on Thursday and I don't go back to the farm until Tuesday.  There has been lots of rain and sunshine, so I bet the seeds are coming up.  Everything seems to grow to quickly on the farm.

Pigment Pondering

No pictures today, which is ironic considering it's a post about plant pigments.  Think of it as an exercise for the imagination.  I promise pictures for next time, but today interesting fonts and colors will have to suffice to spice up the text. 

The previous post (which had lots of pictures), described the amazing plant pigment called betalain, found in Celosias and beets (and bougainvillias and cacti).  Very strangely, betalains have never been discovered in the same plant as today's pigment, anthocyanins.  Anthocyanins are the workhorse, common pigments, and betalains are the superhero pigments.  But anthocyanins are not without some amazing characteristics.  Come along and find out.

Anthocyanins are a group of molecules that are usually red, but sometimes they are blue, orange or even yellow.  They share a similar chemical structure and method of production in plants, and they are everywhere.  Every time you look at a plant and see red, unless you're angry or it's one of the plants with betalains mentioned above, you're looking at anthocyanins.  Red fruit, red leaves, red stems, and red flowers are all due to anthocyanins.

In plants, anthocyanins have many functions.  They can act as sunscreen, which is why immature leaves are often reddish.  Some trees' leaves produce anthocyanins in the fall to protect the dying leaves while their nutrients are recovered by the parent plants.  Anthocyanins are major antioxidants in plants, and they protect the plants' DNA from other types of radiation in addition to UV light.  Flowers use anthocyanins to attract pollinators.  Fruits use anthocyanins to attract dispersers.  Plants that grow amongst snow produce anthocyanins because they help the plant stay warmer and grow faster. 

Some anthocyanins change color with a change in pH.  The one in red cabbage turns red in acidic solution, blue at a neutral pH and greenish-yellow at a basic pH.  You can experiment with this at home with a red cabbage, some vinegar, some water and some baking soda.  The anthocyanins in some hydrangeas are red when the soil pH is around 6.5, and they are blue when the pH is a little lower, around 5.5.  The reason for the hydrangea color change has to do with the increased solubility of aluminum in very acidic soil.  The aluminum is used to make anthocyanins when it's present, which accounts for the blue color.  When aluminum is not available at a higher pH, the anthocyanins are made using iron.

All pigments are molecules that selectively reflect light.  Light coming from the sun, or from a light bulb, is white light, which contains light of all wavelengths.  Pigments absorb white light and hold on to most wavelengths, but a few specific wavelengths are bounced off the pigment.  Whatever those reflected wavelengths are are what your eyeballs detect when you look at the pigment.  Something that's red reflects light with only wavelengths of approximately 700 nanometers (very small).  Something that's violet reflects light with wavelengths of about 400 nanometers (even smaller).  Something that's white is not pigmented - it reflects all wavelengths.  Something that's black is also not considered a pigment - it reflects no light.  That's why looking at something that is black is like looking at a dark room - there is no light coming to your eyes from either.  Black clothes are hotter in the sun than white clothes because the black molecules in the clothes absorb all light that hits them.  The black molecules hold on to the light as heat.  And that is why I'll be wearing a white T-shirt tomorrow on the farm (and I'll bring my camera!).