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Tomato Hornworms

Though not as rampant or widespread as smaller swarming pests, tomato hornworms are almost ubiquitous with gardening as they are easily one of the most recognizable insects of the season. Like all caterpillars, tomato hornworms are not fully formed adults but are merely the transitional larvae prior to the hornworm maturing into a fully-formed five-spotted hawk moth. Because tomato hornworms are a young and developing larvae, they feed quicker and more aggressively than just about any mature insect in the garden. Tomato hornworm is nearly identical to the tobacco hornworm in both color and size, as each can be found almost exclusively on tomato plants and occasionally other members of Solanaceae such as eggplant, pepper, potato, and tobacco. While other foliage-eating insects only consume the softest plant tissue, tomato hornworms are far more ravenous and will feed on the most fibrous parts of the plant.

Facts About Tomato Hornworms

  • Tomato Hornworm Distribution: Widespread throughout all North America
  • Tomato Hornworm Host Plants: Tomato, eggplant, pepper, potato, tobacco
  • Tomato Hornworm Lifespan: 2 weeks as a larval caterpillar
  • Tomato Hornworm Eggs Laid per Lifetime: ~2,000
  • Tomato Hornworm Removal: Bacillus thuringiensis var. kurstaki (Bt), remove by hand, birds
  • Tomato Hornworm Predators: Finches, bluebirds, blackbirds, predatory wasps
  • Most Common Hornworm in North America: Tomato Hornworm (Manduca quinquemaculata)

What Do Tomato Hornworms Look Like?

Both tomato and tobacco hornworms are nearly indistinguishable from one another at a first glance as each are about 3-4” long with vibrant green caterpillar bodies. Though some can be found with dark amber-colored bodies, most tobacco hornworms will be bright exotic green and will all have a pattern of exactly seven white lines marking the length of their body. These white lines have an accompanying black line on tomato hornworms and a green line for tobacco hornworms. Tomato hornworms have a sharp and distinct tail spine referred to as the “horn” which often confuses gardeners as to which end is which, likely influenced by the thought of the horned rhinoceros or narwhal.

Tomato Hornworm Damage

Tomato hornworms are larvae not in their adult stage which means that, like anything still developing in nature, these young caterpillars are voracious eaters. While even the most bothersome grasshopper or snail are picky about which parts of a plant they consume, tomato hornworms are known to devour even the most fibrous parts of a host within hours. Damage caused by tomato hornworms can be difficult to spot because entire leaves will be missing from the plant rather than the chewed up leaves left behind by more forgiving foliage-eating pests. Tomato hornworms also feed on both ripe and unripe fruits in the garden. Don’t let the name confuse you because hornworms do not bury in tomatoes like worms, but are true caterpillars that feed directly on the exterior of the fruit.

What Do Tomato Hornworms Eat?

Tomato hornworms and tobacco hornworms are often confused for one another as they both exclusively feed on crops within the family Solanaceae (nightshade) such as tomato, eggplant, pepper, and tobacco. Though large and 3-4” long, both types of hornworms are still young maturing larvae that must consistently feed before transitioning into an adult moth. Whether a tomato or tobacco hornworm, tomato plants of any kind are the crop of choice for both of these species of caterpillar, as they’re known to quickly and aggressively consume the entire host, including foliage that even the most ravenous infestations won’t consume. Tomato hornworms are not commonly found on eggplant or pepper plants if there are available tomato hosts in the local area.

Tomato Hornworm Eggs

Tomato hornworm eggs are small, green, perfectly rounded, and found in small clusters of 1-5 eggs on the underside of tomato leaves. If you’re lucky enough to spot hornworm eggs early, they look very similar to fish eggs (roe), characteristic of larger garden pests. Since tomato hornworms are immature larvae caterpillars, these eggs are not actually laid by hornworms, but by a fully matured adult five-spotted hawk moth. Hornworm eggs can be difficult to spot because they quickly hatch in less than a week, yet adult hawk moths will lay 1-5 eggs at just about every plant visit, about 2,000 in their lifetime, making it easier to possibly identify a cluster of eggs on the underside of a Solanaceae crop.

How To Get Rid of Tomato Hornworms

Tomato hornworms are some of the largest pests in the garden and can’t be eradicated in the same manner as smaller aphids or spider mites. Hornworms are solitary caterpillars that do not swarm and can be removed individually by hand. For a larger hornworm population, try the store-bought bacterial gardening powder Bacillus thuringiensis, or simply known as Bt. The bacteria is non-toxic to humans and animals but very effective when consumed by caterpillars. There are several types of Bt for different insects but, if eradicating hornworms and caterpillars, be sure to only use Bacillus thuringiensis var. kurstaki. Maintaining an active birdfeeder is one of the most organic means to keep your garden free of hornworms and caterpillars, since visiting birds will naturally check your garden soil for grubs and insects.

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