Finding nemo...toads?

I recently found myself among a group of people in the middle of a hot debate.  Were we discussing current events?  Politics? Religion?  No, we were talking toads...or, rather, todes: Nematodes.  A friend was lamenting the sorry state of his cucumber patch, which was being decimated by cucumber beetles.  He'd heard that nematodes might be the solution.
"Nema-what?" asked someone.
"What are they?" asked another.
"What do they do?"

My mind flipped back through years of gleaned knowledge, like the pages of a book.  "They're organisms that occur in soil...and they're good for the garden," I said, vaguely recalling learning about them in class at The Botanical Garden when I was studying for my horticulture certification.  Yet try as I might, I couldn't recall much else about them.

"Where do you get them?"
"What form do they come in?"

I shook my head, unable to recall much.  "Let me rifle through my old notebooks and get back to you," I said, determined to rediscover whatever I could about these mysterious organisms.  Here's what I (re)learned:

As with most things, the world of nematodes is chock full of drama, and can be summed up by the cliche, "The good, the bad, and the ugly."  Since I'm a positive person in general, I'll get the "bad" out of the way first: The devious above-ground dwellers.  The human-attacking variety is called ringworm (ugh...bet that brings up bad memories of wet towels, steamy high-school gym locker rooms, and the ringworm's pal, athlete's foot).  As most of us know, ringworm is not actually a worm at all.  This multi-cellular organism is unsegmented, but far from harmless.  The variety that attacks plant matter is equally intrusive, with sharply pointed mouth parts that pierce tender vegetative flesh, and can even inject bacteria into plants that can damage--or kill--them.  Far fewer in numbers than the "good" nematodes, the bad-boys tend to get no longer than 1/50 of an inch.

The good guys are 1/25 of an inch to several inches long.  Mostly soil-dwellers (although the bad variety can shift around in moist soil too), they break down organic matter in compost piles, and attack and kill insects such as weevils, clearwing borers, cutworms, sod webworms, white grubs, aphids and...you guessed it...cucumber beetles.  They work by injecting the bugs with harmful bacteria or by entering the hosts and feeding on them.

It's very important to keep a few things in mind when purchasing nematodes.  First of all, get the right kind.  The beneficial ones are from the Steinernematidae and Heterorhabditidae families.  The wrong kind of nematodes will actually attack the plants you're hoping to help--especially vegetables.  Nematodes require moist, humid conditions and warm-ish soil to be most effective, so be sure to water sites before and after application.  The organisms can be found at most nurseries, and even online.  I know Amazon sells them. The packaging is usually a powdery dirt-like substance.

Why would anyone want the "bad" ones?  Perhaps someone wanting an all-natural weed killer.  But a word of warning: just because something is "natural" doesn't mean it's harmless.  Be careful what you wish for when you unleash an army of plant-smashing nematodes onto a site.  After they've eaten their way though all the undesirable plants, where will they turn next?

So, after reviewing the good and the bad of the nematode world, we have only the ugly to explore.  In my opinion, they are all quite homely, but I'm sure there are plenty of nematode advocates who would disagree.  And beauty really is in the eye of the beholder, don't you think?