KC Gardens: Now is the time to watch out for bagworms

06/28/2014 7:09 PM

06/28/2014 7:09 PM

It is one of the most easily identified insects found in the area: the bagworm.

Bagworms are hatching and getting ready to munch their way through many landscape plants. They form a silken bag mixed with plant parts up to 2 inches in length, feeding on different plants. Their favorites are junipers, spruce and arborvitae.

The young, worm-like insects eat the foliage, resulting in an initial browning of the area followed by death of the plant under severe feeding.

Understanding the bagworm’s life cycle is important for control. They spend most of their lives attached to a branch or stem eating, never leaving the comfort of the spun bag. Only the males leave the bags to mate, and then they die. The female lays eggs for next year’s hatch.

Bagworms spend their winters in the egg stage in bags attached to the plant. The eggs hatch in late May through mid-June. The hatchlings are very small at first. They start out about the size of a sharpened pencil lead. They grow quickly, spinning a larger bag until mid- to late summer. The bag is thick, about 2 to 3 inches in length. At that point the bagworms mate, eggs are laid and the whole process is ready to start over for next year.

Their populations build up to damaging levels quickly — each bag of eggs can produce more than a thousand hungry little worms. Controlling them is best done just after they hatch in the late spring or very early summer.

Just about any insecticide will kill the worms while they are small and the silken bag not highly formed. The larger the bag, the less effective the control. By late summer, chemical applications are worthless. At this stage handpicking and destruction of the bags is recommended. This is a slow task that most people would prefer not to do.

To read more on this topic or to get your gardening questions answered on The Star’s KC Garden’s blog by Dennis Patton and other Extension experts, go to KCGardens.KansasCity.com.

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