Btk Biological Insecticide Concentrate 100 ml

Your leeks are perforated, your cabbages are full of holes, the centers of your garlic plants are turning yellow. A caterpillar has passed through, and it won't stop on its own.

Btk stops the damage in a few hours. It is a targeted biological insecticide: it only attacks caterpillars. Bees, ladybugs, and earthworms continue their work as if nothing happened. One spray in the evening on the affected plants, and the vegetable garden gets back on track.

How it works

Btk is based on a bacteria naturally present in the soil, Bacillus thuringiensis var. kurstaki. The caterpillar must eat the product for it to work: it has no effect on contact. You must therefore cover the foliage well, especially the undersides of the leaves, where the larvae hide.

Once ingested, it paralyzes the caterpillar's digestive system. It stops feeding within a few hours and dies in two to five days. The damage therefore stops well before the insect disappears.

What to use it against

• Leek moth, on leeks, onions, chives, and seed garlic
• Cabbage white butterfly and cabbage looper, on cabbage, broccoli, and kale
• Tomato hornworm
• Tent caterpillars, leafrollers, spongy moth

When to apply it

Early. Btk acts mainly on young larvae. A large, well-established caterpillar is much more resistant to it.

In the evening or in cloudy weather. UV rays degrade the bacteria in one or two days.

After every rain. The product washes off. During periods of high pressure, plan to reapply every 7 to 10 days.

For the leek moth, monitor the flight periods announced by the Phytosanitary Warning Network. It is just after the flight, when the larvae are still tiny, that the treatment is most effective.

Combine with insect netting

Btk cures, the net prevents. The most reliable method remains preventing the moth from reaching the foliage: place the Proteknet insect net on hoops before the flight period, and keep the Btk as backup for larvae that get through anyway.

Yellow sticky traps complement the duo well: they indicate when adults are active, and therefore when to act.

What it doesn't affect

Bees, ladybugs, earthworms, birds, pets, and humans. Accepted in organic farming.

A precaution

Btk does not distinguish between a harmful caterpillar and another. It is just as toxic to monarch and swallowtail larvae. Avoid spraying milkweed and neighboring host plants, and treat only the affected plants rather than the entire vegetable garden.

Format and preparation

100 ml concentrate, to be diluted in water according to the label instructions. A sprayer provides more even coverage than a watering can, especially under the leaves.

To learn more

The book Protecting your vegetable garden from pests and diseases covers insect identification and ecological control methods, season by season.