Caterpillars in the Garden or "It Pays to be Pretty"

Sometimes we get our blinders on when we get in the garden.  It is easy to get into an “us versus them” mentality when it comes to insects.  Often when we find a caterpillar in the garden, we consider it a pest and usually try to kill it.  However, I ran into two caterpillars this month that I didn't kill (mostly!).  

The first caterpillar I found in the HELP Garden earlier in the month.  This tomato hornworm is a pest of tomatoes.  If left unchecked, a couple of tomato hornworms can defoliate an entire tomato plant.  What made this particular hornworm interesting were the white tufts covering his back.  These white cottony protrusions are actually the cocoons of tiny braconid wasps. 

Braconid wasps are parasitoids of tomato hornworms.  The female wasp lays her eggs just under the skin of an unlucky tomato hornworm.  When the eggs hatch, the larvae feed on the hornworm – literally from the inside.  As the large mature, they work their way to the skin of the hornworm and spin their tiny cocoons.  After only four days in their cocoons, the newly mature wasps will emerge and fly away.  The weakened hornworm will die. 

As gruesome as this story is for the tomato hornworm, the little wasps are actually very beneficial to the gardener.  The wasps are tiny, less than an 1/8 of an inch long, and pose no threat to humans but they help naturally control the population of tomato hornworms in the garden.

The affected hornworm stops eating soon after the eggs hatch, so a parasatized hornworm does no additional harm in the garden.  If you see a hornworm that is covered with wasp cocoons, leave it in place so the braconid wasps can hatch and help control hornworm in your garden.

The second caterpillar I found in my home vegetable garden.  On my morning walk through, I noticed that my fennel was starting to look a little sparse.  Upon closer inspection I found a little green, black and yellow caterpillar.

 And then I found another one, and another one, and another one!

All of them were chomping away.

The bright color pattern clued me in that this was probably the caterpillar of a butterfly.  A quick visit to my butterfly field guides revealed the culprit, these were the caterpillars of a Black Swallowtail butterfly.  Because I like butterflies (and because the caterpillars had only infested the fennel in one bed), I let the caterpillars survive.  I guess the moral of this story is that it pays to grow up into a big, beautiful butterfly rather than a small, nondescript moth. 

Only a couple of days after that, the caterpillars had defoliated both of the fennel plants in that bed and had started in on the parsley.  Since I don’t eat much parsley, I left them alone.  

The largest caterpillar had already formed a chrysalis.  (Most butterflies only take about four weeks to reach maturity from an egg under ideal conditions.) 

 This morning, I inspected my now leafless (and soon to be lifeless) fennel plants but other than the chrysalis the caterpillars are gone.  Apparently the cowpeas, tomatoes and pepper plants left in that bed weren’t to their tastes.  When I went to check the other bed however, I found a big, fat caterpillar starting to chow down on my last remaining fennel plant.  Even I have my limits, I practiced a mechanical control technique – I picked the caterpillar off the fennel and carried him to the chicken yard.  The girls took care of the rest.

Did someone say caterpillar???

Hey, you have to have balance.

Happy gardening.