Tomato Hornworm Parent?

Sphinx Moth

Sphinx Moth

Before you are able to appreciate that glamorous butterfly or majestic moth, there is a voracious caterpillar (larva) that needs copious amounts of food before it can molt into maturity. As a gardener, it’s important to be able to identify insect visitors to know whether to be on guard rather than simply admire.

A few days ago, this rather large sphinx moth was positioned on one of the deck posts right behind my trailing petunias. Being nocturnal, she decided to stay all day, so I had plenty of photographic opportunities, but no real macro photographic ability without disturbing her. Sometime after 9:00 p.m. that night she flew off.

After studying numerous photographs and references, I still can’t decide whether she is a Carolina Sphinx Moth (Manduca sexta) or a Wave Sphinx Moth (Ceratomia undulosa). There seems to be a wavy pattern in her design, but then many Carolina Sphinxes claim a similar distinction. Her proximity to the petunias suggests that she could well be a Carolina, which, like the White-Lined Sphinx Moth (Hyles lineata) featured in a post last year, feeds on petunia nectar. Adult Wave Sphinxes tend not to feed at all.

Tomato Hornworm Photo Courtesy of Colorado State University Extension

Tomato Hornworm Photo Courtesy of Colorado State University Extension

Why is this important? Well, the Carolina Sphinx Moth is parent to the Tomato Hornworm, that large, knobby green caterpillar that can wreak havoc on a tomato plant. The Wave Sphinx caterpillar prefers lilac and ash leaves.

I don’t mind sacrificing some lilac leaves in a good cause; I have plenty to spare. All of this year’s growth has already occurred, and a healthy supply of nutrients has been stored up for next year. An attack on my ash tree is less welcome, given the continuing threat from the Emerald Ash Borer; but, again, the tree is looking surprisingly healthy after last year’s EAB treatment.

Where I draw the line is my tomato plant. I’m growing one lone heirloom tomato this year, and so far it’s doing beautifully; but it is my only tomato, and I’m not willing to share with a hungry caterpillar. Just to be safe, I’ll be monitoring the underside of leaves for pearly colored eggs and be ready to handpick any horny green caterpillars. Another few weeks of attention and I should be enjoying my first ripe tomato.

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