Their name can be a bit misleading. True, the favorite food of the tomato hornworm is the tomato plant, but they will also feed on potatoes, eggplants, and peppers. Also, they’re not technically worms–they’re caterpillars. The tomato hornworm goes through 5 stages of life: the egg stage, larvae stage, caterpillar stage, pupae stage, and finally the adult stage (moth). The tomato hornworm is most detrimental to your garden plants while maturing from larva into caterpillars.
As the larva grow and mature, changing into caterpillars, they require more and more nutrients, meaning, they’re going to eat more and more. The larvae are usually pale yellow or green when they first emerge from the egg, but as they grow (and eat your garden greens) they become a darker green in color. You’ll recognize a tomato hornworm by its rows of “V’s” along each side of it’s body and by its horns. Some of these pests can grow up to 3 inches in length and be as thick as your index finger! Yuck!
How To Catch a Caterpillar:
As usual, early detection is the key to control. Beginning in late Spring, and continuing through the Summer months, check your plants for eggs and young larvae. Hand-picking them off will do the trick. Do this on a regular basis. Discard of the hornworms by dropping them in a bucket of soapy water. Remember, as the larvae grow, they eat more. You don’t want to “put it off” only to find the damage has been done.
Just like with aphids (see previous blog) lady beetles and lacewings are a beneficial insect to keep around your garden. They will make a meal of your hornworms and help control the population. Check with your local garden center to see if these insects are carried by them or if they can be ordered.
Also, braconid wasps are an excellent insect to have around. These wasps will actually lay their eggs on the body of the tomato hornworm. When in their cocoon stage, the eggs will feed on the tomato hornworm, as parasites. Once the wasps are born, they kill their host and simply move on to the next one, laying eggs and continuing the life cyle. If you see a site like the one below, you are fortunate enough to have braconid wasps taking care of your tomato hornworm issue. Leave the caterpillars alone, allowing the wasps to do their job, and you will hopefully end up with long term pest control–for free!
In addition, your every day common wasp will also feed on tomato hornworms in their larval and caterpillar stage.
Typically, hand-picking and beneficial insects will get the job done, but if you find that you still have too many tomato hornworms, and that they are causing too much damage, then definitely introduce an organic pesticide. Just be sure to use a very low-toxin and quick-acting natural pesticide. Some examples are: Safer Brand Caterpillar Killer, Green Step Caterpillar Control, and Bonide Bacillus Thuringiensis Concentrate.
As an added preventative measure, try to roto-til your soil after you’ve harvested. This will eliminate up to 85% of the burrowed pupae, reducing the amount of adults born, reducing the amount of eggs hatched, and so on.
And The Pest Control Continues…
Next on our agenda, cutworms. Until then, take care and happy gardening.