Stop Caterpillar and Cutworm Damage to Garden Veggie Plants

Your brand new, just-planted vegetable starts have holes in the leaves! Who is eating them? It’s caterpillars and cutworms who come out at night to feast on your tender, baby plants! And worse, they can eat a young plant to the ground, killing it overnight. There’s no need to let this happen. Here is the safe, natural, organic spray I use to give my bell pepper, tomato, green bean, squash and cucumber starts the best protection and stop caterpillar damage to plants:

Stop Caterpillar Damage to garden veggie plants

Instantly Stop Caterpillar and Cutworm Damage to Garden Veggie Plants

Caterpillars, cut worms, army worms – they are all larva and they want nothing more than to eat your young vegetable plants to death. Chances are you had holes appear in your leaves almost the moment your small tomatoes and baby pepper plants were put in the ground. I hate these hungry, destructive pests. Here is what I use to kill them naturally without harming my organic garden:

use 4 teaspoons of BT per gallon of water in a garden sprayer

Organic BT Spray

Ba cillus thuringiensis, also known as BT, is a naturally occurring, soil-borne bacteria that is harmless to plants and humans but causes death when ingested by cutworms. The bacteria causes lethal digestive disruption in caterpillars, which kills them within 72 hours of ingesting the tiniest amounts.

a cutworm eating a leaf — How cutworms in Magnolia (Houston area), Texas often appear.

leaf damage to a bell pepper plant from a caterpillar — Leaf damage on bell pepper starts that had been planted out less than 72 hours before.

So Easy to Apply!

One bottle of BT is usually enough for 2 years of application for over a thousand square feet of young garden plants during the spring months. I add 4 teaspoons of BT to a 1 gallon garden sprayer which I then fill with water to the 1 gallon line. You then pump to pressurize the sprayer and drench the foliage of your young vegetable plants.

how to mix and spray Bacillus thuringiensis BT liquid concentrate in a garden sprayer for your vegetable plants — So easy to mix! Add the greenish-teal colored BT concentrate to a garden sprayer, fill with water, cap and then pump to pressurize and spray your plants. 1,000 square feet of young plants can be sprayed in less than 10 minutes.

When & How to Apply BT to Stop Caterpillar Damage to Plants

Spraying your veggie plants is best done in the evening shortly before sundown! You need to ensure the liquid drenches the leaves, top and undersides if possible, until the plant is dripping. Once the sun is low on the horizon, the risk of sun scald to your plants is low. But there is just enough warmth and light left that the plant can drip dry and not get mildew in normal climates.

a tomato horn worm eating a stem — Tomato horn worms will kill even established, larger tomato plants, eating almost every green leaf overnight.

Stops Tomato Horn Worms

These neon green destroyers of growing tomatoes can eat an entire plant in a day. BT will kill them too, but you must spray the tomato plants twice weekly and again after it rains. If you are foliar feeding your tomatoes, foliar feed in the morning and spray BT in the evening.

a caterpillar damaging a garden vine — White Cabbage fly larva damaging garden vines.

Effective Against All Caterpillar Type Pests

If white cabbage flies have laid eggs and the caterpillar larva are eating holes in the leaves of your brassicas until they look like lace, use the BT spray recipe above! Be sure to drench the leaves, top and bottom, as much as possible. The eaten leaves will not regrow but the plant should quickly put out new leaves. Be sure to spray the tender new leaves every 48 hours until the pest damage stops. After that, a twice per week treatment every 3-4 days with re-application the day after a rain will keep the plants safe.

If your zucchini plants shrivel up and die about the time they produce one small, first little fruit, squash vine borers are to blame.

Also Works on Squash Vine Borers!

Those horrid little larva that bore into the stalks of your squash and kill them shortly after they produce the first fruit are a menace. BT will also handle them but you have to spray your squash plants every 48 hours and squirt the BT concentrate (straight from the bottle) inside the vine stem if you find a hole. This can be tedious and if you live in a southern state where we have 3 seasons of squash vine borers, it may be easier to plant resistant varieties. I have had White Scallop, Lemon Squash and Zucchino Rampicante varieties grow untouched by vine borers for months. Planting more than one really helps guarantee a harvest before July and August burn everything to a crisp.

Stop Caterpillar Damage to Plants & Leaves

Even if you don’t know what pest is eating your leaves, bacillus thuringiensis is going to help! I’ve seen tiny, lime green caterpillars, thicker cut worms and absolutely enormous tomato horn worms all taken out by BT. After ingesting the BT on the leaves the first night, they tend to burrow and hide while they deal with the digestive distress that ends up killing them. Damage usually does not continue after the first 24 hours.

a bee pollinating pink and orange flowers — BT will NOT harm bees, butterflies or other beneficial pollinators!

Safe for Pollinators and Bees!

BT is completely safe for use around bees, butterflies, wasps, hummingbirds and other pollinators who visit your garden. It does not kill bees! However, it is deadly to Monarch butterfly caterpillars so do not spray host plants where you hope to support these caterpillars. It is not deadly to butterflies or nectar-drinking insects.

What If I want a Chemical Free Option?

If you don’t want to spray anything but are still dealing with infuriating pests, there is a mechanical solution that is 100% chemical-free and organic. You can use a blacklight flashlight (afflink) and hand-pick cutworms and horn worms from your plants. The hornworms entire bodies fluoresce and glow bright greenish-blue at night under a blacklight. Any white or cream colored patterning on cutworms will light up in shades of glowing yellow-green, also making them easier to find in the dark.

The blacklight flashlight I’m using is this one (afflink) with a wide beam and has been serving me well since 2020! I use long tweezers to grab the caterpillars and place them in a jar. The next morning I feed the caterpillars to my chickens as a healthy treat. (Chicken keeping and gardening really do go hand-in-hand!)

No More Dead Baby Plants!

I hope this article has armed you with the info you need to stop the horrible caterpillar damage to your veggie plants. Staying on top of spraying for the first two months after your starts have gone into the garden is usually all that is needed each season!