By Paul
Robertson  Class of 2011

Placed
7-1-12 on website

As an organic gardener, I consider myself a friend of the environment.  Thus,
while we all severely dislike those ugly and  voracious Tomato Hornworms, I have
started a mini-campaign to ask gardeners to NOT get rid of all of them in
your garden.  The reasons are two-fold:

-There is a tiny wasp, called a braconid wasp, that lays its eggs under the skin of
the hornworm.  When the eggs hatch, the larvae eat their way through the
skin of the hornworm.  Once outside, they spin small cocoons that look
like rice on the back and sides of the hornworm.  At this point, the
hornworm becomes so weak that it dies, all thanks to the little wasp.

The point is this: the hornworm is the host for the parasitic wasp.  If we get
rid of all the hornworms in our garden, then there is no host for the wasp.
I thus recommend planting an extra tomato plant just for the hornworms so
that there is a chance for the wasp to find a place to lay its eggs.

Bottom line: if you ever see a hornworm that looks like it has a bunch of rice on its
back, LEAVE IT ALONE and let the wasp larvae do their job.

-The second reason to leave at least a few hornworms in your garden is that they
turn into a beautiful moth known as a sphinx moth or a hawk moth or, my
favorite description, a “hummingbird moth”, since it does indeed
mimic the flight patterns of a hummingbird  The first time that you see
one, you will swear that it is a hummingbird until you look more closely and
see that it has a thin proboscis that can be a few inches long to feed from
flowers. The proboscis stays rolled up until the moth begins its feeding.
If you ever get a chance to see on of these moths, you will be very pleased at how
beautiful they are.  In my garden when I lived in the country, they
preferred four-o-clock flowers to feed on. Therefore, I suggest that you plant
some four-o-clocks next year to see if you can attract some of them. They feed
near sundown.

Of course, you still probably want to get rid of many of the very destructive
hornworms.  One way is to pick them off of your plant  (using
gloves).  I used to cut them in two, but it makes somewhat of a mess.
A product with bacillus thurengiensis (BT) such Thuricide can also be
used to control them.

If you want to learn more about gardening in an environmentally friendly manner,
the Springfield Organic Gardening Club meets on the fourth Thursday of each
month at 7:00 pm at the Library Center on South Campbell, or you can get on our
e-mail list at or follow us on
Facebook.

Paul C Robertson

Master Gardener Class of 2011

Coordinator, Springfield Organic Gardening Club