Hornworms Management in Eggplant: Symptoms, Treatment, Cultural, Chemical, and Biological Control

Hornworms are a common pest of eggplant that can cause significant damage to the plant’s foliage. These large caterpillars are known for their voracious appetites and can quickly consume large amounts of leaves, leaving behind only the large veins. The two most common hornworms that attack eggplant are the tobacco hornworm and the tomato hornworm, which have distinctive markings on their bodies.

While the adult moths are strong fliers, the larval stage causes the most damage to eggplant. Infestations tend to be more severe in warm inland areas, with two generations occurring in most areas each year. In this article, we will discuss the life cycle and habits of hornworms and methods for managing and preventing their damage to eggplant crops.

Hornworms Management in Eggplant

The life cycle of Hornworms

The life cycle of hornworms starts when the adult moth lays eggs on the foliage of host plants, such as tomato, tobacco, and eggplant.
After 2-8 days, the eggs hatch, and the larvae emerge to begin feeding. The larvae can grow up to 4 inches (10 cm) long and prefer to feed on the foliage of plants, but they will also feed on pepper, potato, and some species of Solanum weeds.
The larvae go through several instars, or stages of growth, over a period of 3 to 4 weeks. They use their chewing mouthparts to consume large amounts of foliage, leaving only the larger leaf veins behind. Once fully grown, the larvae burrow 3-4 inches (8-10 cm) deep into the soil to pupate. The pupal stage lasts for several weeks, and adult moths emerge in the summer months.

Identification of Hornworms in Eggplant field

The adult moth is a strong flier with a wingspan of up to 5 inches (12 cm). The female moth lays eggs on leaves, and there are typically two generations of hornworms each year in most areas. Infestations tend to be more severe in warm inland areas, and larvae are usually most common in mid-summer, but there may be a small population peak in late summer.

Damage symptoms of Hornworms in Eggplant field

Hornworms in eggplant fields can cause significant damage to the plants. As they feed, the larvae can defoliate the plants, leaving only the large leaf veins behind.
The foliage may have a skeletonized appearance with large holes and missing sections.
Also, hornworms can scar fruits by chewing irregular holes or gouges, making them unsellable.
Dark green or black droppings can also be seen on the plants, especially where the larvae are feeding.
If not managed properly, hornworm populations can quickly become out of control and cause significant yield loss in eggplant crops.

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Hornworms Management in Eggplant by Cultural Method

Monitor for hornworm damage: Check eggplant plants regularly for defoliation or fruits with large cavities.
Handpick larvae: Remove larvae by handpicking them from plants. This is easiest during dusk and dawn when larvae are actively feeding.
Spot-treat-infected plants: Infestations tend to be spotty, so treating only affected plants rather than the entire field is important.
Plow field after harvest: Tillage practices like plowing move pupae to the soil surface, where they freeze during the winter, resulting in up to 90% mortality.
Rotate crops: In areas with high overwintering populations, rotating to non-solanaceous crops can help reduce hornworm populations in eggplant fields.

Hornworms Management in Eggplant by Biological Method

Biological control of hornworms in eggplant involves using natural enemies to manage the pest population. One of the most effective biological control methods for hornworms is using parasitic wasps, including Trichogramma and Brachonid wasps. These wasps lay their eggs inside the hornworms’ eggs or on the back of the larger caterpillars, and the developing larvae feed on and kill the pests.

Another natural control method uses insect predators like lady beetles and lacewings that feed on hornworm eggs and small larvae. These predators can be attracted to the eggplant field by planting flowers that provide nectar and pollen for their adult stage. It is important to note that when parasitized hornworms are found, they should be left in the field as they will produce more wasps that can lay eggs on and kill other hornworms.

Using biological control methods can be an effective and environmentally friendly way to manage hornworm populations in eggplant fields. However, monitoring the population and using additional methods, if necessary, is important to achieve effective control.

Hornworms Management in Eggplant by Chemical Method

Chemical management options for hornworms in eggplant include the use of insecticides. Several insecticides are available with different modes of action, including spinosad, indoxacarb, teflubenzuron, tebufenozide, methoxyfenozide, and novaluron. It’s important to note that using insecticides can harm beneficial insects and pollinators and may lead to insecticide resistance in hornworm populations.

Preventive Measures for Control of Hornworm

Use row covers: Covering plants with floating row covers can prevent adult moths from laying eggs on the plants and reduce the likelihood of an infestation.
Monitor plants regularly: Check plants for hornworms and their damage symptoms regularly, especially during mid and late summer when they are most active.
Encourage natural enemies: Plant flowers and herbs that attract parasitic wasps and other natural enemies that prey on hornworms. Avoid broad-spectrum insecticides that can kill these beneficial insects.
Use insecticidal soap: Spraying plants with insecticidal soap can kill smaller worms and reduce the infestation.

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Conclusion

Hornworms can cause significant damage to eggplant plants by feeding on leaves, fruits, and stems. Handpicking and using cultural and biological methods, such as crop rotation and parasitoid wasps, can effectively manage hornworm populations. If chemical control is necessary, following label instructions carefully to minimize the impact on the environment and beneficial insects is essential. Taking preventive measures like tilling the soil and monitoring plants for early signs of infestation can also help control hornworms and protect eggplant crops.

Hornworms Management in Eggplant: Symptoms, Treatment, Cultural, Chemical, and Biological Control

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