Tomato Hornworms: Identify & Exterminate These Garden Pests
Is your tomato crop being devastated by hordes of hornworms? You’re not alone! Every year we grow tomatoes on Thistle Downs Farm, and every year we end up in an epic battle with tomato hornworms. So here are a few tips and tricks to identify and control tomato hornworms in your garden.
What is a Tomato Hornworm?
Tomato hornworms are invasive garden pests that feed on the foliage (and sometimes fruit) of tomato plants. They also feast on other nightshade crops including peppers, eggplants, potatoes, and even tobacco.
Tomato hornworms are actually larvae hatched from the eggs of the adult hawk moth, also referred to as the hummingbird moth because of it’s resemblance to a hummingbird. In late spring, the hawk moth lays eggs on the underside of foliage, which hatch soon after and unleash their gluttony on tomato plants.
The hornworms feed for about a month or two before burrowing into the ground to form a cocoon. The cocoon will remain in the soil over winter and hatch the following spring, and the cycle continues.
Tomato Hornworms vs. Tobacco Hornworms
There are a couple different types of hornworms that reak havoc on nightshade crops in North America. The two most common are tomato hornworms and tobacco hornworms. They both look very similar but with a few key differences.
Tomato hornworms have small light spots running down the sides of their bodies. They have a BLACK horn protruding from their tail.
Tobacco hornworms on the other hand have small black spots between parallel white stripes. They have a RED horn protruding from their tails.
For practicality purposes though, they are often lumped together because they behave the same in the garden and pest control recommendations are the exact same.
Identifying Hornworms in Your Garden
Hornworms can be difficult to spot because they do a remarkably good job at blending in with the foliage on tomato plants.
There are a few tell-tale signs though that will alert you to a hornworm infestation.
You may notice the leaves on the tops of your tomato plants have a significant amount of insect damage, or they are stripped of leaves entirely as in the picture below. This is a good indication of a hornworm infestation.
You may also notice fruit damage as seen in the following picture. This hornworm was particularly brazen!
Another good indicator of a hornworm problem is the presence of hornworm poop on leaves, fruit, or even collecting on the ground.
All of these signs indicate a tomato hornworm infestation and if not dealt with swiftly, you can say goodbye to your entire tomato crop.
Tips to Control and Prevent A Hornworm Infestation
Till Your Garden
One of the biggest preventative measures you can take is to till your garden prior to spring planting. This will destroy most of the cocoons in the soil and significantly reduce the hornworm moth population.
Remove Them
If you notice hornworms in your garden, one of the most basic and effective things you can do is pick them off one by one. As I mentioned, they do a really good job of blending in so you’ll inevitably miss a few, but every time you see one just remove it.
They don’t bite or sting, though the larger ones may pinch a little bit as they try to grab ahold, so I would suggest wearing gardening gloves. They will also stain your hands a terrible green color, though my dad doesn’t seem to mind…
To dispose of the hornworms you pick off, you can smash them (which is messy), feed them to your chickens, or drop them into a bucket of soapy water. The soap will kill them pretty quickly. The soapy water method is usually our disposal method of choice.
Use Insect Spray
There are also several organic and inorganic foliar sprays you can use to poison the hornworms when they ingest it. If you decide to go this route, make sure to check which pesticides are approved for your area.
The main organic pesticide that people typically use to control hornworm problems is BT or Bacillus thuringiensis (no affiliation), which is a naturally occurring bacteria that kills hornworms when ingested. BT is sprayed onto the foliage of plants and only affects insects that eat the leaves. Therefore, it is harmless to beneficial insects in the garden.
Other Natural Ways to Reduce Hornworm Problems
Promote Beneficial Insects
Ladybugs are an invaluable insect to welcome into your garden. They eat the Hawk Moth eggs on the underside of leaves which reduces the hornworm population in the garden.
Wasps are another beneficial insect to have around the garden for hornworm control as well. The picture below is a hornworm covered in wasp eggs. Female wasps will actually lay their eggs under the skin of the hornworm and when they hatch, the larvae will eat the hornworm from the inside out.
Companion Planting
Companion planting is another great way to deter hornworms from feasting on your garden. Try planting marigolds or fragrant herbs like basil or dill between your tomato plants to act as a natural insect repellent to hornworms and other garden pests like aphids, whiteflies, and beetles.
Conclusion
Hopefully you’ve learned a little bit about tomato hornworms and maybe you’ve picked up a trick or two that will help sway the battle in your favor when fighting these destructive pests.
Keep fighting the good fight and if you have any tips or tricks of your own to get rid of hornworms, please shout them out in the comments below.
Happy Gardening!
Cody
Thistle Downs Farm
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