By MIKE COURSON
Great Bend Post
Many a camper will spend a summer evening wrapped up in a sleeping bag. So, too, does the bagworm. The destructive pests hatch in mid-May through early June and begin emerging from their bags over the next several weeks. Alicia Boor, agriculture and natural resources agent in the Cottonwood District for K-State Research and Extension, said now is the time to spray for the worms.
"A smaller tree or bush, they can kill it," she said. "Over time, even a large tree with enough infestation, they can kill it by defoliating it. Especially with evergreens, they don't grow back their needles. They grow new ones at their base, but if you kill off the tip, it doesn't work very well."
Bagworm larvae, when they are an eighth to a fourth of an inch in size, produce a fine strand of silk they can use to move to other host plants. While feeding, the worms construct silken bags that are covered with dead needles. In mid-August to early September, when the bags are 1-2 inches long, the larvae stop eating and seal the bags.
"If you've seen the bags in the past, then you know that next spring you need to be looking for them," Boor said. "Once they're the big bags, other than picking them off, there's not anything you can do. No insecticide is going to penetrate that."
Boor said insecticides should be applied once a week for four weeks when the larvae are small because they emerge at different times. During the winter, the bags can be picked off the tree or nearby buildings and soaked in soapy water or burned to help with the infestation. Click here for more information on effective pesticides.