10 Best Caterpillar Killer 2026 in the United States

Bonide Captain Jack's Thuricide BT is a liquid spray designed to control caterpillars and worms in home gardens, especially suitable for organic gardening. Its active ingredient is Bacillus thuringiensis (BT), a naturally occurring bacterium that targets specific pests like cabbage loopers, hornworms, and tent caterpillars without harming beneficial insects. The product comes ready-to-use with a built-in sprayer, making it easy to apply directly to fruits, vegetables, trees, and ornamental plants.

One of its biggest benefits is that it’s safe to use even up to the day of harvest, which is great for those growing edible plants organically. It starts working quickly, usually within 2-3 days after spraying. However, because it’s a microbial insecticide, it doesn’t leave a long-lasting residual effect. This means that after heavy rain or in cases of severe infestation, you’ll need to reapply it every 5 to 7 days to keep caterpillars under control.

This product is a strong choice for home gardeners looking for a targeted, environmentally friendly caterpillar killer that’s gentle on beneficial insects and safe around food plants.

The Monterey B.t. Biological Insecticide is a liquid concentrate designed specifically for organic gardening. It utilizes Bacillus thuringiensis (B.t.) as its active ingredient, which is known for effectively targeting caterpillar and worm-type pests like cabbage loopers, bagworms, and gypsy moths. This makes it highly effective in protecting a wide range of plants, including vegetables, ornamentals, and shade trees. The formulation is organic and OMRI listed, ensuring it adheres to strict organic gardening standards, making it a suitable choice for eco-conscious gardeners.

One of its standout features is its safety profile; when used as directed, it does not harm birds, earthworms, or beneficial insects such as bees and ladybugs, thus maintaining ecological balance in your garden. The liquid form allows for easy mixing and application using various sprayers, though it requires careful adherence to label directions to ensure effectiveness and safety.

One potential drawback is the need to reapply the product following heavy rains or as new foliage emerges, which could mean more frequent applications. Additionally, while it is very effective on caterpillars, it may not address other pests that gardeners might be concerned about. The one-gallon volume offers a good supply for covering larger areas, but the 8.6-pound weight might be cumbersome for some users to handle. The Monterey B.t. Biological Insecticide excels in organic caterpillar control with a strong safety profile, although it requires diligent application and might not be a one-stop solution for all pest issues.

The AzaGuard Botanical Insecticide Nematicide Concentrate is a potent option for organic gardening enthusiasts. Its active ingredient, Azadirachtin, is a well-known insect growth regulator (IGR) that effectively targets a wide array of pests including aphids, armyworms, beetles, caterpillars, mealy bugs, mites, thrips, and whiteflies. This makes it a versatile choice for anyone dealing with multiple pest issues. Formulated at 3% concentration, it is twice as strong as many competing brands, ensuring effective pest control by inhibiting insect growth, feeding, and reproduction.

The product's organic certification (OMRI listed) and EPA registration add a layer of trust and safety, particularly for users concerned about using non-toxic solutions in their gardens. It is also convenient to use, given that it can be applied as a spray directly onto affected plants. However, while the AzaGuard is effective, it may not be the quickest solution for severe infestations due to its nature as an insect growth regulator, which works over time. Additionally, the product's residual effect is not extensively detailed, so users might need to reapply it periodically to maintain its efficacy.

This product is best suited for organic gardeners looking for a non-toxic, versatile, and EPA-approved pest control solution.