One hornworm can strip a plant of it’s leaves in just a few hours – they are eating machines. Because of their ferocious appetites, hornworms can grow to a large size in just a few days.
They can reach sizes of 6 inches long and almost an inch in diameter. Hornworms can be very difficult to prevent, but they can be slowed down.
If you have found a hornworm munching on your precious vegetable plants, here are some tips for getting rid of these pesky critters:
Tips for Finding the Hornworms
One of the best practices is to check your plants daily (twice a day is even better) for any signs of hornworms.
Don’t worry – you’ll notice if they are present very quickly. Check for any chewed leaves. Just the “meaty” parts of the leaves will be chewed off, the veins of the leaf will most likely still be present.
Obviously, check to see if you spot the caterpillars themselves. Hornworms can be tough to spot at first because they blend in very well with the plants. Make sure to look closely, and check under the bottom sides of leaves.
Also, look on the ground and on leaves for any signs of hornworm droppings. It will be very noticeable for a large hornworm. It looks similar to tiny rabbit poo – small black or dark brown pellets.
Another way to spot them is to spray the plant with soapy water. The soapy water will cause the hornworms to wiggle and convulse around, making it easier to spot them.
If hornworms are found immediately remove them from the plant and either drop them in a container of soapy water or smoosh them.
One thing to watch for when handling hornworms, when you grab them they will turn around and eject a dark brown or black liquid on your hand.
It’s advised to use gloves or tweezers to pick them up with, unless you want that goop on your hands.
Tips for Organic Hornworm Control
Of course, besides handpicking the hornworms you find, you’ll want to prevent them from getting to your nightshade vegetables in the future.
Here are a few things that will help to control their presence in your vegetable garden:
Take Action Before the Hornworms Emerge
You have probably heard the expression – “A good defense starts with some good offense”, right?
It’s no different when battling a pesky caterpillar that wants to eat up your harvest. Follow these tips when preparing your vegetable garden for planting:
When tilling, or loosening the soil where you grew tomatoes the previous year watch for the pupae of the hornworm in the soil.
They are brown torpedo-shaped, sac-like objects that look sort of like a little tube. Here’s a site with some great pictures of the hornworm pupae.
They can be difficult to catch, but careful cultivation may find a few. Have an extra set of eyeballs with you to hunt for the pupae.
- Rotate the crops in your vegetable garden, and avoid planting tomatoes, or other nightshade vegetables in the same area.
The moths may still fly around and find your tomatoes anyway, but crop rotation will still have its benefits.
Use a black plastic mulch for your nightshade vegetables. By covering the soil with black plastic garden mulch it can help prevent the moth from emerging in spring and laying eggs on your plants.
If the area is covered then the moth can’t emerge and will die.
Use a Homemade Moth Deterrent
You can use a mixture of garlic, insecticidal soap, and cayenne powder diluted with water to keep the sphinx or hawk moth out of your garden and from laying eggs.
This will help to control the hornworms from entering your vegetable garden to begin with.
Put the mixture in a garden sprayer or a bottle sprayer that attaches to a water hose, and spray your plants.
The moths hate the smell of the solution, and will not get near it.
Attract Insectivore Birds to Your Yard
Place a couple bird feeders, or bird baths, around your vegetable garden in strategic locations.
Some birds, including robins and mocking birds, can spot the worms and devour them for lunch.
Plant a Trap Crop
You can also plant a big patch of dill as a trap crop on one end of your vegetable garden.
Hornworms absolutely love dill, and might go for the dill plants instead of the tomatoes or peppers.
Diversions are legal when fighting garden pests.
Attract Parasitic Wasps
Public enemy number one for hornworms are the parasitic wasp. The parasitic wasp lay their eggs on the backs of hornworms, which the caterpillar will carry around until the eggs hatch. Once the wasp eggs hatch, they will kill the hornworm for food.
Use a Pop-up Net
Gardener’s Supply offers a Pop-up Bird Net that surrounds the plants in a moth-free setting.
There are a couple downsides to using the Pop-up Net. One is the cost – if you have a large tomato garden it could get expensive.
Secondly, if there are hornworm pupae in the soil where you place the Pop-up Net you could inadvertently trap the moth in with the tomato plants, giving it free picking on the plants.
So, if you use the Pop-up Nets make sure to cultivate the soil well, and add black plastic mulch on top to keep hornworms at bay.
Use Biological Warfare on Hornworms
I’m not saying you need to buy gasmasks, but you may need to use Bacillus thuringiensis, or Bt.
Bt is an organic pesticide that is completely safe to use on vegetables. Bt is mixed with water then sprayed on the tomato plants. When the hornworm eats a leaf with Bt, the hornworm losses its appetite and dies.
The awesome thing about Bt is it only harms insects that eat the leaves, so beneficial insects and pollinators are not harmed.
Thuricide, commonly called Caterpillar Control, is a good form of Bt to use for hornworms.
Using a Combination Battle Plan
As you can see there are many different ways to defend against hornworms. Unfortunately, it may take several, or maybe even all of them to successfully keep hornworms from devouring your precious tomato plants.
Even with several control methods in place you may still need to observe and handpick hornworms from your plants from time to time.
For more information about hornworms, please visit the Hornworms page.