Tomato Hornworms are a very common pest that gardeners have to deal with regularly. These pests can decimate an entire crop quickly if they are not kept under control. Even though they are referred to as the Tomato Hornworm, they attack other similar plants in the nightshade family (Solanaceae), including potato, and tobacco.
Last year I wrote an article about organic solutions for controlling caterpillars and hornworms, but that should be used as a last resort in controlling them. Anytime we are trying to garden organically, we should use the least invasive technique possible to achieve the desired pest and disease control results.
While Bacillus Thuringiensis, otherwise known as BT, is a completely organic and natural pest control measure, there is also an expense to consider in purchasing it which must be taken into account. It also does not specifically target tomato hornworms, but kills all caterpillars, including those who become Monarch butterflies and other butterflies who are very beneficial in our gardens.
With this in mind, the best thing for us to do is to first employ a targeted eradication method first so that we are only getting rid of the actual pests that we are trying to eradicate instead of using a "weapon of mass destruction" to wipe out everything all at once. If you have caterpillars which produce beneficial butterflies who will help to pollinate your garden and produce a larger harvest for you, why would you want to harm them when tomato hornworms are the problem? If other types of caterpillars are found in the garden, they can simply be relocated out of the garden.
Tomatoes hornworms are caterpillars, but they do not produce beautiful butterflies that are going to pollinate your garden, instead, Tomato Hornworms are the caterpillar stage of the 5 Spotted Hawk Moth shown below.
These moths have no benefits to your garden. They have a wingspan of between 4 to 5 inches wide and they have between 5 to sometimes 6 pairs of yellow bands on their abdomen. Adults fly at dusk, and females deposit eggs singly on the upper surface of host plant leaves. The caterpillars are called Tomato Hornworms and each has a black horn at the end of the abdomen. Caterpillars have huge appetites for leaves and fruits and can defoliate plants quickly. Fully-grown caterpillars pupate and overwinter in soil burrows. They can be found from Mexico north throughout most of the United States and occasionally into southern Canada.
The best way to deal with garden pests is by not having the problem in the first place. This can be accomplished by having more healthy microbiology in your soil. The healthier your soil biology is, the healthier your plants will be. The healthier your plants, the more pest and disease resistant they can be.
By increasing the health of the biology in your soil, you can increase the Brix level in your plants. The Brix level basically is the amount of sugars in your plants. I will be doing another article soon all about the Brix level, and how you can increase the Brix levels in your plants. Most insects do not like to feed on plants with a high Brix level. Instead, they tend to move onto other plants that taste better to them. So merely by increasing the Brix level of the plant, you are also making it more pest resistant.
But what happens if you have tried to make your plants more pest resistant and you still end up with tomato hornworms eating on them? Well, before we pull out the "Big Guns" and start spraying everything down with BT, take a look and see how bad the situation really is first.
Typically you will not have a whole herd of caterpillars feasting on your crop. I have rarely ever seen more than half a dozen at the most in my gardens. If you only have half a dozen caterpillars that you need to deal with, there is a much better way of combatting them without using chemical pesticides or even organic solutions like BT. The best thing to do in this situation is to go hunting and simply pick them off your plants by hand.
Now, nature has thought about this, and has created the tomato hornworm in a perfect shade of green to blend in very well to your plants. They have a very effective natural camouflage, but, we have something even more effective available to us than their camouflage, we have science.
The easiest way to hunt for tomato hornworms is at night simply using a small handheld UV flashlight. Tomato hornworms cannot hide from UV light, they glow under it which makes them stand out against the plants making them very easy to see.
Now that you can see them, simply pick them off and dispose of them, it is as simple as that, problem solved, and you didn't have to order any organic pesticide to get rid of them.
A simple UV (blacklight) flashlight can be purchased from Amazon or several suppliers online. They are typically listed as UV Pet Urine Detectors and generally sell for $10 or less.
If you happen to live in Hawaii, or the South West where scorpions are a concern, the UV light also is very effective in spotting them as well as scorpions also fluoresce under UV light just like the tomato hornworms do.
In addition to the BT and other organic solutions that I keep on hand for serious problems, I also keep several UV flashlights around for the occasional simple pest situation.
One word of caution regarding UV flashlights. While they are a useful tool in the garden, they also cause any biological fluids to fluoresce, so make sure you never take one with you if you ever stay in a motel. Let's just say if you do, you will not be able to sleep afterward.