A New Twist on Tomato Hornworms
April showers bring more than just May flowers; they also bring plenty of pests into your gardens.
If you spy those pesky little hornworms clinging to your tomato plants, donít immediately reach for the pesticide, says Dr. Xing Ping Hu, an Alabama Cooperative Extension System entomologist.
"In most cases, tomato hornworm larvae harbors parasitic wasps," she says. "If you find a pretty big hornworm on your plant, donít spray it or squash it. Instead, gently pick it off and place it in a container with a host leaf."
Cover the container with a screen so the larva cannot escape, she says. Or simply cage the larva on the leaf with a screen cloth.
"Later on you will see a number of white projections protruding from and distributed over the whole larval body," Hu says. "These are the cocoons of the small parasitic wasps. Several days later you will see a lot of tiny black parasite wasps emerge from the cocoon. The screen cover will allow the parasite wasps to escape."
The wasps will kill the hornworms when they emerge from the cocoons, and will seek out other hornworms to parasitize.
"It is an automatic-conduct biological control of the hornworm," she says.
The container of larvae should be placed in your garden, Hu says.
"The container can be any kind of glass jar or plastic bottle," she says. "Last year, I found only one tomato larva, which was already 3 inches long, on my green pepper plant. I simply caged it on that plant and three days later, I found white cocoons projecting over the body. I counted 47 cocoons on it while the hornworm when the hornworm was about to die."
A few days later, Hu says she watched the beneficial parasite wasps emerge from the cocoons.
"They flew through the tiny holes of the screen on their way to freedom," she says. "This is a fun biological experiment to do with kids. I invited my neighborís children to come and see this great example of natureís own pest control system."
Hu says tomato hornworms produce only one generation each year.
"They pupae during the winter," she says. "Adults emerge in late spring and lay eggs on plants. The larvae do the damage in summer to early fall, so gardeners will notice big hormworm larvae in mid- to late-summer.
SOURCE: Dr. Xing Ping Hu, (email@example.com), Extension Entomologist, Alabama Cooperative Extension System, (334) 844-6392