After much anticipation, tomato season is finally here but something has been devouring the leaves on your tomato plant and even taken bites out of the green tomatoes. Looking for the culprit you see an enormous alien-looking green caterpillar with white stripes and red dots down its back.
Tomato hornworms and their equally hungry cousins the tobacco hornworm can do lots of damage in a depressingly short amount of time. Tomato hornworms feed most often on tomatoes but will also eat eggplant, pepper, and potato plants as they are in the same family.
Identification: They are voracious eaters and blend in with the foliage so well you don’t know they are there until you see bare stems. Sometimes you notice their calling card first…a pile of green or dark brown droppings on the leaves or ground known as insect frass.
Control: The easiest way to control hornworms is to use garden scissors, clip off the infested stems and dispose of the pests. However, before you run for your scissors and head out to your garden wait…there is something else you should know.
Remember the small creature you saw hovering over your flowerbed that looked like a tiny hummingbird? There are many types of hummingbird moths. Not all feed on tomato plants but some of these fascinating creatures are the product of the same caterpillar you found wreaking havoc on your tomatoes. They are called sphinx moths, hawk moths, or hummingbird moths. They do not land on the flowers as their tongues can be up to 4 inches allowing them to drink nectar while they hover over the flowers. Most prefer to feed in the evening but some feed in the day.
Hummingbird moths and tomato hornworms are the beauty and the beast of the insect world and can create quite a dilemma for gardeners. We are fascinated by sphinx moths but want to destroy every tomato worm we can find.
Fortunately, there are options.
- Tilling the soil after harvest will destroy most pupae that may have overwintered.
- If you allow them to stay on the plant nature may solve the problem for you. Parasitic wasps often lay their eggs on hornworms. Similar to a real-life horror movie, the wasp larva will feed on the hornworm from the inside out then forming a chrysalis or cocoon on the caterpillar’s body. If you find a tomato hornworm parasitized by wasps leave it alone. The caterpillar will stop feeding and when the wasps hatch they will go on to destroy more hornworms. Nature has a way of balancing the equation.
This option may sound extreme, but for a unique child activity, consider saving a few tomato worms in an old aquarium with 3-4 inches of damp soil. Feed them tomato leaf clippings you prune from your vines. It may be worth the effort when they see the metamorphosis first hand and release the beautiful sphinx moth into your garden.
Note: the last photo is of a Bumblebee Hummingbird Moth/Clearwing Snowberry and does not feed on tomato plants or members of the solanacea family but various shrubs rarely causing severe damage.