This post contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. Learn more.
Garden centers have a whole aisle of “organic” insect killers, and they are not interchangeable. Each works on different pests in different ways. Use the wrong one and you’ll waste money, and possibly harm the bees and ladybugs that are on your side. Here’s how to match the product to the problem.
At a glance
| Product type | Best for | How it works | Watch out for |
|---|---|---|---|
| Insecticidal soap | Aphids, whiteflies, mealybugs, spider mites | Breaks down the insect’s outer coating; contact only | Must hit the pest directly; can burn sensitive or hairy-leaved plants; avoid heat over 90°F |
| Bt kurstaki | Caterpillars (hornworms, cabbage worms, loopers) | Bacterial toxin caterpillars eat | Also kills butterfly caterpillars you want; washes off in rain |
| Spinosad | Caterpillars, thrips, leaf miners, some beetles, spider mites | Affects insect nervous system; contact and ingestion | Toxic to bees while wet; spray at dusk, off flowers |
| Neem oil | Mixed soft-bodied pests; some fungal issues | Smothers and disrupts feeding and growth | Can burn plants in heat or sun; avoid blooms |
Insecticidal soap
True insecticidal soap is not dish soap. Products like Safer Brand Insect Killing Soap use potassium salts of fatty acids, which weaken the protective outer layer of soft-bodied insects so they dehydrate. It works only on contact, so coat the undersides of leaves where aphids cluster, and repeat every 5 to 7 days while pests are present. The National Pesticide Information Center notes it breaks down quickly in soil. Test on a few leaves first, since some plants are sensitive.
Check price for Safer Brand Insect Killing Soap →
Bt (Bacillus thuringiensis var. kurstaki)
Bt kurstaki is a bacterium that kills caterpillars after they eat treated leaves. It doesn’t harm bees, ladybugs or people at labeled rates. It will kill any caterpillar, though, including monarchs and swallowtails, so only spray plants that are actually under attack. Reapply after rain.
Check price for Bt caterpillar killer →
Spinosad
Spinosad comes from a soil bacterium and is widely used in organic farming. Bonide Captain Jack’s Deadbug Brew is the best-known garden version. Its label lists caterpillars, bagworms, leaf miners, thrips, spider mites and certain beetles. Spinosad-treated insects may stop feeding quickly but take a day or two to die, so check results after 2 or 3 days before respraying. It’s toxic to bees while wet: spray in the evening, keep it off open flowers, and let it dry.
Check price for Captain Jack's Deadbug Brew →
Neem oil
Neem oil, pressed from neem tree seeds, works as a smothering oil and feeding disruptor against many soft-bodied pests, and some formulations also help with powdery mildew. Apply in the evening, never in full sun or high heat, and keep it off flowers.
Check price for neem oil spray →
Before you spray anything
- Identify the pest. Your local Cooperative Extension office can help, often for free.
- Try a hard spray of water first for aphids. It knocks many off for good.
- Hand-pick big pests like hornworms and beetles.
- Encourage predators such as ladybugs, lacewings and parasitic wasps by planting flowers like dill, yarrow and alyssum.
- Check the label for which crops it’s approved on and how long to wait before harvest.
Always read and follow label directions, including pre-harvest intervals. “Organic” and “OMRI Listed” do not mean a product has no effect on people, pets or beneficial insects.