Is bagworm and shade damage reversible?

Asked June 3, 2019, 5:30 PM EDT

I am a volunteer on advisory board for our non-profit senior citizen apartment building. It was built more than 20 years ago but some of the landscaping that was established then has not been professionally managed, esp. trees and shrubs. We back up to a city park in Rockville. The border with the park is lined with a row of our planted dogwoods, in front of which are a row of evergreens. Photo 1 shows an evergreen with bagworm damage. We tried to handpick the bagworms for several years but have obviously not succeeded; as you can see, the damage is extensive. Is there any way to salvage this specimen? We do not want to go to the expense of spraying if it is past saving. Photo 2 shows shade damage at the back of the other evergreens in the row. The dogwoods have shaded the backs of the evergreens which no longer have green growth. We have not seen bagworms on these but they are looking worse each year, I assume from the shade. Any advice for these ? (short of cutting down our dogwoods which we will not do.) The dogwoods themselves are constantly under attack from vines coming from park property. We try to cut these invasives annually to prevent damage to tops of dogwoods. Any help would be appreciated, even if that means hiring consultants. Do you hire out consultants from the extension service?

Montgomery County Maryland

1 Response

We are not staffed for site visits.

However, a site visit should not be necessary. Your dwarf Alberta spruce will not put out new growth in the part killed by bagworms. (Besides hand-picking, the approach to take with bagworms is to spray with Bt. Search 'bagworms' on our website.)

Your other spruces are overshaded, as you know. There is no remedy for the thinning and dieback you see. The best approach is to cut down the spruce when they no longer are attractive, but are a negative in your landscape.

This should give you better access to the dogwoods, which are the most valuable because they are native. (Dwarf Alberta spruce are not native here. They generally do not do well, ultimately.) Then you can battle invasive vines more easily. If possible, increase the cleared swath around the dogwoods so that managing invasive vines is simplified. The dogwoods are the valuable asset here.