Garden Q&A: On how to deal with bagworms and stiltgrass
By Ellen Nibali
Sep 04, 2019 | 7:00 AM
I pulled all the bagworms off my evergreen shrub and put them in the garbage can. Next day, they were all hanging from the lid like Christmas lights. Can they live on plastic? What do I do about next year? Will the bare area they ate on my evergreen fill in?
We’ve seen them hanging from traffic light poles this time of year. It’s late in their life cycle now. The “worms” (actually moth larvae) are big, mature and less interested in eating than perpetuating the species. They pull in their heads and attach their bags with tough threads, then transform into moths. Only males have wings and they fly to bags containing females to mate. The females lay 200 to 1000 eggs in the bag and both sexes then die. So, those bags are still bags full of trouble.
To kill both bagworms and eggs, drop bags in a bucket of soapy water to drown.
Unfortunately, evergreen areas killed by bagworms do not regrow. If there is a chance some bags escaped you, you may want to spray your shrub preventatively next spring with Bacillus thuringiensis, referred to as Bt. It’s a bacteria-based insecticide that kills a narrow range of insects and is not harmful to humans or animals. Several brands are available.
I’ve been listening to others complain about stiltgrass for years. Well, now I’ve got it — big time. Help! It’s all intermixed with my liriope and spreading into clumps in the flower beds.
Foreign invasive stiltgrass has exploded in Maryland this past year. Now it is producing seeds. It’s an annual, so any seeds you catch now will save you a ton of stiltgrass next year — and for seven years to come. (That’s how long the seed stays alive in the soil.)
Tedious as it may seem, take the 10 or 20 minutes to pull the stiltgrass out of the liriope and your beds. It pulls easily — almost too easily, since it will break off sometimes. Be sure you get the whole plant, including the shallow roots. Bag any stiltgrass with seed heads. Otherwise, it can be composted.
Next year, you can apply a crabgrass preemergent herbicide to your lawn (stiltgrass is undoubtedly there) and your liriope. You’ll have less in your beds and it will be easier to keep ahead of.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.