What are bagworms?
"Many people think that bagworms are the worms that create large webs in trees; those are actually tent caterpillars. Bagworms are the larvae of another moth that feed primarily on evergreens and create a little bag constructed of silk and needles that resembles a cone. That's what makes them so hard to spot."

Are they a problem here?
"Yes, especially in Bourbonnais. I would say that they are reaching epidemic proportions and will have a an economic impact if they are not controlled. We have found them on arborvitae, spruce, fir trees and bald cypress. Many banks, schools, libraries and businesses are unaware that their trees are infested until they become completely defoliated like the arborvitae hedges around Turnberry subdivision."

How do you control them?
"Well, it's not easy. You need to understand how they live to know what to do and when to do it. The eggs hatch in the bags in May and begin to crawl around the plant and feed. As they grow and feed, they begin constructing their own bag from silk and leaves (needles). They drag it along with them and when they are ready to pupate, they affix their bag to a branch and pupate. The male moths fly out in August and September, impregnate the females that remain in their bags, and they in turn lay 500 to 1000 eggs that over winter in the trees."

"So, you can do one of two things. You can handpick the bags from trees that are small enough to reach. Just be sure to destroy the bags completely. Or you can wait until May when the larvae are hatching and feeding to apply a pesticide drench to the ground under trees. It will be taken up into the leaves and the larvae will die from feeding. As always, read the label carefully and follow the directions to the letter."

If you don't already have them, do you need to take these measures?
"Firstly, don't assume you don't have them. As I stated earlier, they are very hard to spot for the first year or two because they look just like cones. We inspected a fir tree at a bank in Bourbonnais and it took us about twenty minutes to spot the bags because they were cleverly hung just behind each fir cone. You can tell the difference though, once you spot them, because they are constructed of needles, not scales like regular cones."

"Also, handpicking is still the best method of control, but the soil drench becomes necessary when the trees are too large to handpick. Spraying is not a good choice because the window of opportunity to directly hit the larvae or the adult males is so slim. Spraying evergreens is also inadvisable in very hot weather."

"Everyone should be scouting for them, but don't use any chemicals in an attempt to prevent them. That doesn't work."