Bagworms

If left to run amok, bagworms can defoliate an entire tree or shrub.

DRC_Janet Laminack

Janet Laminack

The bagworms are back. I have been spotting them in quite a few locations around Denton.

Barely noticeable at first, these insects hang in trees in bags of their own making, created from leaf material from the tree. It is a great camouflage. At the first sight of them (or maybe I should say, if you notice them early) you can handpick them from the shrub or tree. It doesn’t get much more organic than that.

You do need to remove them from the tree area and dispose of them somehow. They may not look like it, but they are alive.

We had several brought into our office a few years ago to be identified. After identifying them, we threw the sack in the trash. It was creepy later to hear all this commotion; like zombies, these innocent-enough looking clusters of leaves had risen from the (seeming) dead and were seeking vengeance.

Long story short (and less dramatic): You need to squish them. Because bagworms generally overwinter in the egg stage, every bag you remove in the winter holds the potential for hatching 500 to 1,000 eggs the next spring. Might be worth paying your child a quarter per bagworm to pick them off.

If bagworms are left to run amok on shrubs or trees, they can spread quite quickly and defoliate the whole plant. They particularly enjoy junipers and arborvitae, but I have seen them on roses and other plants. And this is where I tell you the sad tale of the female bagworm who doesn’t get to see much of the world. Not only is she wingless, but she had to make her own bag to live in and that is where she stays. Meanwhile, the male bagworms turn into moths and flit around wherever they please.

If handpicking is not for you, there are other control options. Bacillus thuringiensis (Bt), a bacteria, is especially effective on smaller bagworms. Spinosad is another effective low-impact insecticide. Spinosad is a natural substance made by a soil bacterium that is toxic to some insects, caterpillars being one. I should mention here that bagworms aren’t really worms, they are caterpillars — the larval form of the moth.

Bagworms aren’t a problem every year, but take a quick look at your landscape plants and make sure you don’t have any of these bad guys (or gals rather) hanging out.

The Master Gardener help desk is available to help you identify insects, diseases, plants and provide you with best management practices. Call us at 940-349-2892 or email master.gardener@dentoncounty.com. Visit www.dcmga.com to get more information about gardening in North Texas; now is the time to put in your fall garden.

JANET LAMINACK is the horticulture county extension agent with Texas AgriLife Extension. She can be reached at 940-349-2883 or via email at jelaminack@ag.tamu.edu.

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