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Big Bad Bugs 2


Second in an Occasional Series

Tomato Hornworms are perhaps the most shocking bug to find in your garden. They are just huge (or at least they are by the time you find them). And the amount of damage an individual hornworm can do is astonishing. They eat both leaves and fruits (never all of one, but parts of two or three, I hate that). They are in the garden now, so you need to keep your eyes peeled for them.

Healthy & Parasitized Hornworms

Healthy (left) & Parasitized (right) Hornworms

Unfortunately, they are almost impossible to spot when small because they blend in very well with your tomato plants. Generally, I notice their damage first and then I know to look for them and even then they can be hard to spot.

I’ll never forget when I saw my first hornworm. I looked at one on my tomato plants and I thought a deer had come by and chomped on the top of my plant. As I looked over the plant I spotted the hornworm. I tried to pull it off of my plant, but I could never get all of its legs off the plant at the same time so I wound up just cutting off the leaf that it was on. I have continued to do the same to this day.

Tomato Hornworm Damage

Tomato Hornworm Damage (relatively minor in this picture)

Sometimes (I’d actually say about half of the time) you’ll find the hornworm covered with what look like white cocoons. That is exactly what they are, the cocoons of the Braconid wasp. The adult wasps lay their eggs in the hornworm where the larvae hatch, eat their way out (think Alien) and form the cocoon to pupate.

Do not destroy a hornworm with these cocoons, because the hornworm is about to die anyway and you want the wasps to reach adulthood so they can kill next year’s hornworms.You’ll notice in the hornworm picture above how much larger and healthier looking the unparasitized hornworm looks.

There are various ways to dispose of healthy hornworms, but since I’m a bit squeamish about what would happen if I squished a hornworm, I just take any hornworm I find far away from my tomato plants, so it can’t crawl back and I figure it’ll just starve to death. Alternatively, you can apply BT (Bacillus thuringiensis) which is a naturally occurring bacteria that when eaten by any kind of caterpillar will kill it. I figure though that by using BT, it just gives the hornworm a couple of extra days to my plant before it dies. You can buy BT sprays at most nurseries these days.

The adult form of the Tomato Hornworm is a moth called the Sphinx, Hawk, or Hummingbird Moth. I prefer Hummingbird Moth because it’s the most descriptive, as they can actually hover like a hummingbird. I saw one feeding on my chive flowers last year so I would advise not planting your tomatoes near your chives.

Though individual hornworms can do a lot of damage, they usually won’t appear is such high numbers that you have to worry about losing a whole crop. So keep out your eyes for Tomato Hornworms but don’t panic when you find one.

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