It happens, you walk into your tomato patch and you notice that one of your plants no longer has leaves. What is going on? you probably have an infestation of tomato hornworm. Don’t be alarmed you can save your tomatoes, and all is not lost. Let’s talk about hornworms and how to get rid of them.
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Two Species of Hornworm
Tomato hornworm: larvae of the five spotted hawk moth or sometimes called the hummingbird moth. Full grown caterpillars have v shaped markings on their sides with five red spots, and a blue/black horn on last abdominal section.
Tobacco hornworm: larvae of the Carolina sphinx moth. Full grown caterpillars have straight white lines on their sides with a red horn on the last abdominal section.
Good news is that they act identical, so the elimination strategies work the same for both.
How do I know I have them?
The hornworm usually starts their destructive leaf eating at the top of your tomato plants. You will notice that the plants are missing their leaves and all that is left is the stem. They also will eat some of the actual tomato fruit. They never eat all of the tomato just enough to ruin it.
Around the base of the plant, you will notice dark green or black droppings. Litte pellets everywhere. They love to eat so they poop…a lot.
What is a hornworm and where do they come from?
The moths emerge from the soil in late spring or early summer. They lay their eggs on the underside of the tomato leaves. The eggs hatch in one week and the caterpillars will reach full size in 3-4 weeks.
Fully grown hornworm larvae will drop to the ground, burrow, and form a cocoon to turn into a moth. If the weather is warm this process may take only 2-3 weeks. So, if you live in a warm climate more than one generation may be possible. So be diligent in watching for hornworms.
How to eliminate hornworms?
The best way to eliminate hornworms from your tomatoes is to hand pick them off of the plants, place them in a bucket, and feed them to your chickens. If you don’t have chickens, then you can put them into a bowl of soapy water to kill them or you can smash them.
Because they camouflage so well on your plants a popular method of finding the hornworm is to go out at night with an UV flashlight. The hornworm glows in the light and are easily seen. The light allows you to see the smaller caterpillars that you may miss in the daylight.
How do I prevent hornworms?
In my research one source said that tilling the soil in the spring destroys the overwintered larvae. A 90% mortality rate. I’m not sure how effective this method is because we tilled this spring and I have hornworms on my tomatoes as I write this post. Maybe we will have less? I’m not sure.
Plant dill, basil, and marigolds as companion plants to repel hornworms.
Attract beneficial insects such as the braconid wasps, ladybugs, and lacewings. How do you attract these insects? By planting native flowers in your garden that bloom throughout the season so they have a constant supply of food and will want to visit your garden regularly.
The braconid wasp actually lays rice like eggs on the back of the hornworm. This will eventually kill the hornworm. The ladybugs and lacewings will eat the small larvae and eggs of the hornworm. So, find out what native flowers grow in your area and add them to your garden so you can attract the beneficial insects.
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