07/22/2026
Have you ever seen a bug glow in the dark??
Under UV light, tomato hornworms fluoresce with an eerie glow, making them surprisingly easy to spot during nighttime āhornworm hunts.ā What feels like sci-fi is actually a trick many gardeners use to find these masters of camouflage.
A few fascinating facts:
ā¢ Tomato hornworms are the caterpillar stage of the five-spotted hawk moth.
ā¢ They can grow over 4 inches long!! One of the largest caterpillars in North America.
ā¢ During the day, their bright green bodies blend almost perfectly with tomato foliage.
ā¢ At night, UV light causes their bodies to fluoresce, revealing exactly where theyāre hiding.
Why do farmers care? Because a single hornworm can strip leaves, chew through stems, and scar developing tomatoes in just a few days. A handful of caterpillars can quickly defoliate an entire tomato plant, reducing the plantās ability to photosynthesize and produce healthy fruit.
Hereās the cool part: not every hornworm should be removed.
If you find one covered in tiny white cocoons, leave it alone! Those arenāt eggs, theyāre the pupae of beneficial braconid wasps. The wasps developed inside the hornworm, eventually killing it, and then go on to parasitize more hornworms. Theyāre one of natureās best forms of biological pest control.
Organic farming is often about working with nature rather than against it. Sometimes the most effective pest management comes from protecting the predators already doing the job for us!
