Hot July makes bagworms happy

In Gardening, science plants, video on July 21, 2011 at 3:57 pm

Bagworms (Thyridopteryx ephemeraeformis) are especially bad this year. My three mature Thuja occidentalis “pyramid” trees are now dead due to infestations. In the past, I picked and killed bagworms by hand, up to 50 a day. They were usually concentrated in a small area of one of the trees. This year the population exploded. There were 1000 or so of the critters on each tree. Too bad for them, they ate so much that most of them did not grow to maturity and are abandoning their dead prey. Today I gave up and cut down 2 of the trees. In the video you can see the worms crawling off- I hope to their death in our 100-degree weather. I squished a few, which quickly attracted yellow jackets to feed. Maybe the yellow jackets will move onto the live ones too! Ideally I would burn the tree carcasses to kill the remaining worms, but we are in a drought and it is not safe to burn. We had an abnormally hot and dry June, which probably stressed the trees, perhaps weakening their resistance to pests. Alternatively, the hot, dry conditions may have favored bagworm egg emergence.

Although I enjoyed these trees, they obstructed the view at the end of the driveway. With a new 15-year-old driver in the family, it was probably a good idea to get rid of the trees anyway. I generally avoid pesticides in my yard, but if I had really wanted to help the trees I could have sprayed with a systemic insecticide early in the spring, before the bugs began devouring the trees. Perhaps they were doomed no matter what I did; Further reading indicates that trees rarely survive over 3 years of bagworm infestations.

© 2011 Sharon Settlage.  All rights reserved.

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