**Tomato Hornworms** (*Manduca quinquemaculata*) are the large, green larvae (caterpillars) of the Five-spotted Hawkmoth. They are a significant, voracious pest of plants in the nightshade family, including **tomato**, potato, pepper, and eggplant. The conflict is severe, rapid **defoliation**: the caterpillars are highly cryptic (camouflaged) but can consume massive amounts of foliage and sometimes the fruit itself in a very short period, leading to stunting, sunscald damage to exposed fruit, and substantial yield loss.
Taxonomy and Classification
Tomato Hornworms belong to the order Lepidoptera (Moths and Butterflies), family Sphingidae (Sphinx or Hawkmoths). They undergo complete metamorphosis. The large, active larvae are the destructive stage, while the adult moth is a strong flyer and nocturnal pollinator.
Physical Description
Adult Larvae are large, 3 to 4 inches long.
- **Larva (Key ID):** Large, green caterpillar with prominent **white V-shaped markings** along the sides and a conspicuous black or dark blue **”horn”** (not a stinger) on the posterior end.
- **Adult Moth:** A large, gray-brown hawkmoth with a 4-5 inch wingspan, distinguished by **five pairs of yellow spots** on the abdomen.
- **Damage Sign (Key ID):**
- **Stripped Stems:** Sudden, severe defoliation, often leaving only bare stems and large, noticeable droppings (frass) on the ground or leaves below.
- **Girdled Fruit:** Occasional feeding on the surface or near the stem of green tomatoes.
- **Conflict:** Rapid, severe defoliation and crop loss.
Distribution and Habitat
Tomato Hornworms are found throughout temperate North America. Their habitat is the foliage of cultivated nightshade crops and some wild nightshades, where the larvae feed.
Behavior and Conflict
The conflict is dominated by the hidden damage and voracious appetite.
- **Cryptic Nature:** Their size allows them to consume an entire plant rapidly, yet their green coloring and V-shaped markings provide excellent camouflage, making them hard to spot until major damage is done.
- **Life Cycle:** They typically have two generations per season, meaning control efforts may need to be repeated.
Management and Prevention
Control is integrated pest management (IPM), favoring manual removal and biological controls.
- **Manual Removal:** The most common and effective method for small gardens. Look for the large, black droppings (frass) as the best sign of their presence, then remove the caterpillar and destroy it.
- **Pruning:** Remove and destroy any eggs found on the underside of leaves.
- **Bt:** Apply the microbial insecticide *Bacillus thuringiensis* (Bt) to the foliage. Bt is specific to caterpillars and must be consumed to be effective.
- **Wasp Parasitism:** Preserve and protect hornworms that have small, white, rice-like cocoons attached to their backs. These are cocoons of the **Braconid Wasp** (*Cotesia congregata*), a powerful natural enemy.
Conservation and Research
Tomato Hornworms are managed as major garden and agricultural pests. Research focuses on optimizing the use of *Bt* strains and enhancing the populations of key natural enemies like the Braconid wasp.