August—Time for Brown Bags on Trees

On my journeys throughout Upper Milford Township, I can’t help but see the different varieties of coniferous trees. There are various shades of green, different lengths of needles, and some even have cones hanging down.

But at this time of year those brown bags begin to appear on some of them.  And as time goes on, those beautiful pines and spruces can become brown and completely defoliated.

This year, our front trees were “chosen.” We have four Douglas fir, four blue spruce and four arborvitae. Nearly all have been “decorated” with the brown bags. 

We realized we were infested and needed advice from the experts. So we called the Penn State Cooperative Extension Service and my father (we always need our parents no matter how old we get). Besides, my dad once had a small orchard and I know he had bagworms at some point.

Both experts told us how to rid the trees of our unwanted guests. The best way, they said, is to pick off the bagworms and burn them.  The worms would sometimes pop their heads out of their bag. Yuck!! But we did it … at least the ones we could reach. So far, we have filled over a five-gallon bucket with those creatures.

We were also told to spray the affected trees once a week until there are no signs of the bagworms. So it was off to the store to purchase the proper insecticide.

These bagworms are very destructive, attacking many deciduous trees that lose their leaves in the fall and grow new ones in the spring, as well as evergreen trees and shrubs. Some of their favorites include: arborvitae, cedar, fruit and nut trees, juniper, locust, maple, pines, willow and others.

The young caterpillars feed on needles and leaves, stripping plants of their foliage. They can be recognized by the characteristic “bag” they construct around themselves. This bag is made from silk and material from the plants they feed on. 

Bagworm eggs, produced by females in the fall, are sealed in their bags during the winter months. In late May/early June, tiny caterpillars hatch and build a bag around their hind parts, carrying it around while feeding on the foliage of trees throughout the summer. 

In August, the mature larvaean immature form of an insect often referred to as a grub with few physical characteristics of the adult attach their bags to a branch where they remain for about four weeks in a pupa stage. This is when they eat the needles and leaves of the trees.

We noticed as we were removing the bags and tossing them to the ground that the bagworms crawled back to the trees and reattached themselves to the branches! It was then that we learned all the bags must be immediately burned.

Later, the male wriggles out of the bag and develops into a moth, then seeks out a female to mate. Because he cannot eat due to an underdeveloped mouth, he dies after reproduction.

The female does not develop into a moth, but remains inside her bag. After mating, she produces 500 to 1,000 eggs and dies. 

I have no idea what their purpose is. They eat the needles and leaves of trees, mate and die. What a life!