They can be hard to find, but you'll know when your garden has them.
Tomato and tobacco hornworms can decimate plants in just a few days.
Gardeners and extension agents said this is the beginning of a three-week period when the caterpillars are at their hungriest.
Chesapeake's Paul Johnson has been picking them off his two dozen backyard tomato plants for several days.
"This is moth week, so there's a lot of procreation going on," said Johnson, 59, who has been gardening nearly his entire life. "They'll eat potato plants, tomato plants and moon flowers. I pick them off and put them on the moon flowers because I don't mind them eating those."
Hornworms also will feed on peppers and eggplants.
The easiest way for backyard gardeners to get rid of them is by hand – but the trick is finding them.
"We basically use scouting and prevention to deal with them," said Virginia Beach extension agent and farmer Roy Flanagan.
Industrial-sized gardens may have to be sprayed with insecticides, experts said.
Green like plant stems, hornworms easily blend in with foliage. Their bodies have spots that resemble eyes to confuse predators. Each has a single tail spike, which is the origin of the insect's name. The spike is red on a tobacco hornworm and blue on a tomato hornworm.