Sacramento Digs Gardening logo
Sacramento Digs Gardening Article
Your resource for Sacramento-area gardening news, tips and events

Articles Recipe Index Keyword Index Calendar Twitter Facebook Instagram About Us Contact Us

Attack of the tomato hornworms!

August heat brings out spike in population of these giant caterpillars

Green caterpillar on tomato plant branch
The tomato hornworm's coloring makes it hard to see among tomato leaves. Look
for its poop on leaves below or, at night, search using a UV flashlight. (Photo: Debbie Arrington)

They look like something out of a sci-fi movie – if you can spot them. And what they do to tomato plants is absolutely horrifying.

Recent hot, dry weather brought out a late-summer surge of one of the biggest bugs in our vegetable gardens: The tomato hornworm.

They love these last days of summer – and munching away on ripe tomatoes. While many critters retreat in high heat, these invaders actually spike in numbers and activity as the mercury rises.

Natural enemies usually keep their populations under control. But hornworm numbers tend to go up in August along with the temperature.

I saw this firsthand in my own Sacramento garden. I've picked off five hornworms from my tomato vines in five days.

Fat as a finger and just as long, hornworms rank as Sacramento’s largest caterpillars. They eat big bites out of their favorite food: Juicy tomatoes. They’ll also eat hard green tomatoes, leaves and stems.

Their stripes let them hide in plain sight. They blend in so well with their surroundings, they can seem impossible to spot.

What’s easy to see are leaves that have been stripped bare to the stem and damaged tomatoes. Other pests and critters may take bites out of tomatoes, but those stripped leaves – especially if the damage seems to appear overnight – usually indicate hornworms.

If you suspect hornworms, look for their poop. They leave large black or green droppings on or around the plant. If you see those droppings, carefully inspect the plant’s nearby leaves and stems. When you find it, pick off the hornworm and dispose of it. (Folks who raise chickens say their hens love them as a snack.)

If the hornworm escapes capture, it burrows into the soil and pupates into a moth of equally gigantic proportion: The hawk moth. Emerging in spring, this brown and gray moth has a 5-inch wingspan.

Rototilling the tomato bed after harvest prevents those moths from ever developing – and laying eggs next spring.

For more on tomato hornworms:


0 comments have been posted.

Newsletter Subscription

Sacramento Digs Gardening to your inbox.

Taste Fall! E-cookbook

Muffins and pumpkin

Find our fall recipes here!

Local News

Ad for California Local

Thanks to our sponsor!

Summer Strong ad for

Dig In: Garden Checklist

For week of Dec. 10:

Take advantage of these dry but crisp conditions. It’s time to get out the rake!

* Rake leaves away from storm drains and keep gutters clear.

* Fallen leaves can be used for mulch and compost. Chop up large leaves with a couple of passes with a lawn mower.

* Prune non-flowering trees and shrubs while they’re dormant. Without their foliage, trees are easier to prune.

* Rake and remove dead leaves and stems from dormant perennials.

* Make sure to take frost precautions with new transplants and sensitive plants. Mulch, water and cover tender plants in the late afternoon to retain warmth.

* Succulent plants are at particular risk if temperatures drop below freezing. Don’t water succulents before frost; cover instead. Use cloth sheets, not plastic. Make sure to remove coverings during the day.

* Clean and sharpen garden tools before storing for the winter.

* Brighten the holidays with winter bloomers such as poinsettias, amaryllis, calendulas, Iceland poppies, pansies and primroses.

* Keep poinsettias in a sunny, warm location. Water thoroughly. After the holidays, feed your plants monthly so they'll bloom again next December.

* Just because it rained doesn't mean every plant got watered. Give a drink to plants that the rain didn't reach, such as under eaves or under evergreen trees. Also, well-watered plants hold up better to frost than thirsty plants.

* Plant garlic (December's the last chance -- the ground is getting cold!) and onions for harvest in summer.

* Bare-root season begins. Plant bare-root berries, kiwifruit, grapes, artichokes, horseradish and rhubarb. Beware of soggy soil. It can rot bare-root plants.

Taste Spring! E-cookbook


Find our spring recipes here!

Taste Summer! E-cookbook


Find our summer recipes here!