Hornets are very pesky and difficult pests to get rid of. They have a voracious appetite and can do a lot of damage quickly, but it is possible to save your plants.
In this complete guide, we’ll tell you everything you need to know to get rid of caterpillars organically. You’ll learn about the caterpillar’s life cycle, their diet, and the damage they cause. Plus, we’ll show you five safe, natural ways to rid your garden of caterpillars.
We’ll also share some simple prevention tips to help you keep hawk moths from infesting your plants in the future.
What are hornets?
Hawkmoths are a type of caterpillar in the Sphingidae family that eventually develop into large moths.
There are two species: the tomato hornmoth (Manduca quinquemaculata) and the closely related tobacco hornmoth (Manduca sexta).
The tomato hornet is found in southern Canada, northern Mexico, and many other parts of North America. The tobacco hornet is more common in the southern states and is the species that causes the most damage to tomato plants in those areas.
What do they look like?
Both the tomato hornmoth and the tobacco hornmoth (larvae) are large caterpillars that can grow up to 5 inches long and are so named because they have horns on their rears.
They look very similar – both are green with white markings on their bodies – but there are two easy ways to tell them apart for sure:
The tomato hawk moth has a V-shaped pattern on its body and black horns, while the tobacco hawk moth has diagonal stripes and red horns.
The larvae eventually develop into adult sphinx moths, also known as hawk moths or hummingbird moths, which are brown or gray with striking patterns and a wingspan of 4 to 5 inches.
The eggs are hard to see, but can be found on the undersides of the leaves of the host plant. The eggs are smooth, spherical, and pearly white in color. When they hatch, the tiny larvae are pale green in color.
Life Cycle
There are four main stages in the life cycle of a hawkmoth: egg, larva (caterpillar), pupa, and adult. The larva is the only stage that feeds on plants, while the adults are actually beneficial pollinators.
Adult females lay eggs on the undersides of leaves from late spring to early summer, and the eggs usually hatch within a week.
The larvae then begin to feed on the host plant, growing rapidly and molting several times. After about 4-6 weeks, they reach the pupal stage and build a cocoon in the soil. Depending on environmental conditions, this stage can last from 2 weeks to several months.
Finally, the adult moths emerge and live for about two to three weeks. In milder climates, this occurs in the spring and only one generation occurs per year, but in warmer areas, multiple generations may overlap throughout the summer.
What do caterpillars eat?
Hawkmoth larvae have a voracious appetite and feed mainly on plants of the nightshade family.
These include tomato and tobacco plants, as well as related vegetables such as eggplant, peppers and potatoes, but they have also been seen feeding on other plants, including brugmansia and grape vines.
Despite their common name, tomato hornworms will happily feed on tobacco plants and vice versa.
The larvae feed primarily on the leaves of the host plant, often devouring several leaves in a night, but may also eat stems, fruits, and flowers.
Where do they come from?
Because the adults can fly, hawk moths can come from anywhere and are very difficult to eradicate completely.
They are naturally attracted to nightshade plants, so if you’re growing these plants and there are hawk moths in your area, they’re more likely to find your garden.
Damage to plants
Due to their green/brown body coloring, wasps are well camouflaged and difficult to spot among the foliage on which they feed, but there are some signs of the damage they cause that you may notice even before the insects appear.
Gnawed or missing leaves at the top of the plant – this is where the caterpillars’ preferred feeding begins. The caterpillars will kill entire stems or leaves on small plants in a very short time. Plant growth will be stunted or the whole plant will droop. Irregular holes will appear in the fruit where the caterpillars have fed on the flesh. The presence of droppings (excrement) is also a common sign. The droppings are usually large dark green balls.
How to get rid of wasps
It’s important to get rid of hawkmoth infestations as soon as you notice them, otherwise they can quickly cause significant damage to your plants.
Below are some safe and natural remedies using organic and non-toxic remedies.
Insecticidal soap
Applying organic insecticidal soap can help get rid of caterpillars, but the soap must come into direct contact with the insects to kill them.
Spray the plant thoroughly with the solution first thing in the morning or late in the evening, being sure to cover the stems, the tops and bottoms of the leaves, and any visible caterpillars or eggs.
Insecticidal soap has no residual effect, so we recommend regularly checking your plants for signs of renewed activity and reapplying if necessary.
Hand-picked
If you don’t have a lot of plants, picking them off by hand is an easy and effective way to get rid of the wasps.
Don’t worry, despite those fearsome horns, they won’t bite or sting, but wear gloves if you don’t want to touch them.
The best time to hand-pick them is in the early morning or late evening when they are most active. Gently pull them off the leaves and drop them into a bucket of water and mild liquid soap.
Diatomaceous earth
Diatomaceous earth (DE) is a non-toxic powder made from fossilized algae that dehydrates and kills pests.
If you are using this to get rid of wasps, sprinkle the powder lightly on the plants, especially on the tops and bottoms of the leaves, the stems, and the base of the plants.
Be careful not to use too much diatomaceous earth as it can also harm beneficial insects in your garden.
Beneficial nematodes
Beneficial nematodes are microscopic worms that feed on the larval and pupal stages of pest insects.
Prepare according to package directions and apply to the soil around the base of plants.
Learn more about using beneficial nematodes to control wasps and other garden pests.
Bacillus thuringiensis (BT)
Bacillus thuringiensis (BT) is a type of bacteria that occurs naturally in the soil. To be effective, the grubs must ingest BT, so apply in the late afternoon or early evening when the grubs are likely to be feeding.
Follow the prep instructions on the package and spray your plants liberally, making sure both the tops and undersides of the leaves are covered.
Related Article: Natural Garden Pest Control Methods and Recipes
How to prevent hornworms
All of the above treatments are effective at getting rid of caterpillars, but the best thing you can do is to stop them from feeding on your plants in the first place. Here are some prevention methods you can try:
Encourage natural enemies
Try planting herbs like dill, parsley, fennel, and other flowers around your vegetables, which attract insects like lacewings, ladybugs, and parasitic wasps that prey on wasps.
Use insect hotels or leave some areas of your garden slightly wild to attract predators. Attract birds to your garden with bird feeders and water bowls.
Related article: How to release ladybugs into your garden
Protecting plants
Early in the season, protect your plants with a lightweight horticultural fabric or row cover, which allows light, water, and air through while preventing adult moths from laying eggs on the leaves.
Once your plants start to flower, be sure to remove the cover to allow pollinators to reach them.
Try repellent plants
Companion planting is a good way to protect your crops from hawkmoths, using strongly scented flowers or herbs to scare away the adult moths.
Try planting basil, borage, chives, garlic or marigolds next to the plants you want to protect – all of these have pungent scents that repel pests, with the added benefit of attracting predatory insects.
Cultivating the soil
Digging and breaking up the soil at the beginning and end of the gardening season is a great way to control hawk moths.
This will expose and destroy the pupae in the soil, reducing the number of pupae next season.
FAQ
Hawkmoths can be harmful because their larvae feed on plant leaves and fruit. These large caterpillars have voracious appetites and can cause a lot of damage quickly. However, the adults are harmless to plants and can even be beneficial pollinators.
No, the caterpillar cannot sting or bite humans, its horns are not poisonous and are used as a bluff against predators.
If they are not causing significant damage to your plants, it is not necessarily necessary to eradicate them, but most people choose to do so, as they can kill a plant quickly, especially if there are multiple larvae on one plant.
The tomato hawk moth changes into the five-spotted hawk moth, and the tobacco hawk moth changes into the Carolina hawk moth. These are large moths that hover while feeding, like hummingbirds, and are usually most active in the evenings and after dark.
About garden pest control
Share your tips on how to get rid of caterpillars in the comments below.
