The marigold is a humble flower that is often overlooked, but it is a powerful weapon in the fight against the devastating tomato pest, the tomato hornworm. This large, green caterpillar can quickly defoliate a tomato plant and ruin the crop. But the marigold has a trick up its sleeve – it produces a chemical called alpha-terthienyl, which is toxic to the hornworm.

When the hornworm eats the marigold leaves, it ingests this chemical. The alpha-terthienyl binds to the hornworm’s gut wall and damages the cells. This causes the hornworm to stop eating and eventually die.

The marigold is a safe and effective way to control tomato hornworms without the use of pesticides. It is also a beautiful flower that can add beauty to any garden. So if you are growing tomatoes, be sure to plant some marigolds nearby to help protect your crop.

Here are some tips for using marigolds to control tomato hornworms:

* Plant marigolds around your tomato plants.

* Plant marigolds early in the season, so that they have time to establish themselves before the hornworms arrive.

* Pinch off the flowers of the marigolds to encourage the plants to produce more leaves.

* If you see any hornworms on your tomato plants, remove them by hand and drop them into a bucket of soapy water.

By following these tips, you can help protect your tomato plants from the devastating tomato hornworm.