Tobacco Hornworm on a Tomato Plant Tobacco Hornworm on a Tomato Plant

Tobacco Hornworms & Tomato Hornworms

September 10, 2012

I was in the garden a couple days ago and my dog, Jasmine, was a little too interested in my tomato plants.  I headed over to that area of the garden and Jasmine had found massive green caterpillars...  The plants had become home to tobacco hornworms!

Both tomato hornworms and tobacco hornworms feast on tomato plants.  In fact, they love anything in the Solanum family.  And they have voracious appetites.  An infestation of hornworms can quickly defoliate a plant.  These caterpillars are the larval stage of sphinx moths which are huge moths with a wingspan up to five inches.

The hornworms can be difficult to spot due to their green color, they blend in extremely well.  But it is easy to tell where they have been.  Clusters of stems will have missing leaves from where the caterpillars have chewed them off.

Once you have spotted the hornworms, they are very recognizable.  They are up to four inches in length, bright green and a "horn" on their backside.  The tomato hornworm has stripes that form a "V" and a dark green horn.  The tomato hornworm has "dashed" stripes and a red horn.

Controlling hornworms is simple enough.  Get a bucket of soapy water and handpick the caterpillars from your plants.  Yes, I know...  Ew.  Pick the caterpillar off the plant and toss it in the bucket.  It will probably take a couple visits to the plants with the bucket to make sure you've gotten all of them. 

They will be easier to spot early in the morning and in the evening when the plants are shaded.  Hornworms will move to the outer parts of plants to feed making it easy for you to swoop in and pick those guys off.

If you have an infestation and your tomato plants are in immediate danger of becoming caterpillar dinner, Bt can be applied.  Bt (short for Bacillus thuringiensis) is a bacteria that caterpillars ingest and essentially seizes their digestive track, stopping them from eating your plants.  Bt is non-toxic and safe for most beneficial insects.  And it is non-toxic to birds that eat the infected caterpillars.

I have a love/hate relationship with the mockingbirds in my garden.  They love to eat my fruit during strawberry season.  But they also love to keep my plants picked clean of caterpillars!  So don't discount the advantages of hungry birds in the garden.

Now that you know what too look for, a watchful eye (and a strong stomach) will keep your tomatoes from turning into caterpillar fodder!

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