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Written by Mousumi P., Somerset County Rutgers Master Gardener
The Somerset County Rutgers Master Gardener Helpline has been getting many inquiries lately about Boxwoods. Boxwoods, with its many species and cultivars, are broad-leaved evergreen shrubs mostly used as foundation planting and backdrops for planting beds and formal gardens. Unfortunately they are often susceptible to several pests like leafminers, psyllids and boxwood blight disease. All of these concerns, in addition to the emerging threat of the Box Tree Moth raise the questions: what can be done, and what are some alternatives to these common landscape shrubs?
Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org
Brian Kunkel, University of Delaware, Bugwood.org
Boxwood Leafminer
Boxwood leafminer insects (Monarthropalpus flavus) feed on the tissue between the outer surfaces of the leaves. The feeding leads to blotch-shaped mines in the leaves and cause leaf drop from heavy infestation. For infested boxwoods, prune back about 1/3 to remove and dispose the affected stems. For larger infestations, Spinosad based pesticide can be applied.
Nancy Gregory, University of Delaware, Bugwood.org
Boxwood Psyllid
The Boxwood Psyllid insect (Psylla buxi) feeds on the leaves and buds of the boxwood causing the leaves to curl and cup. Luckily the damage caused to the boxwoods is mostly aesthetic. Infested branches can be pruned out and disposed. For larger infestations, horticultural oil and insecticidal soap can be applied.
David L. Clement, University of Maryland, Bugwood.org
Adria Bordas, Virginia Polytechnic Institute and State University, Bugwood.org
Boxwood Blight
Boxwood blight is caused by the fungus Cylindrocladium pseudonaviculatum. The damage begins with leaf spots followed by rapid browning. Leaf drops start on the lower branches and move up the canopy. Also, narrow black streaks (cankers) develop on the green stems. Repeated defoliation and dieback can kill the entire plant. For diagnosis and management, contact landscapers and lawn care professionals, as the infected plants needs to removed, including fallen leaves.
Alternatives to Boxwoods
If you’re removing a boxwood due to any of these common issues, or if you’re looking for a low-maintenance hedge and would rather avoid the boxwood, there are luckily many alternatives available. The three listed below are all hardy for New Jersey and considered to be deer resistant.
Inkberry Holly, Ilex glabra
- Full sun to part shade
- NJ Native.
- Cultivar ‘Gem Box’ has small boxwood-like leaves and dwarf habit.
Bayberry, Myrica pennsylvanica
- Full sun to part shade
- Salt tolerant for coastal areas or near roads treated with de-icing salt
- NJ Native.
- The female plants produce a small gray waxy fruit that is attractive to certain birds and was traditionally used to make candles.
Plum Yew, Cephalotaxus harringtonia
- Shade Tolerant
- Dark green, flattened needle-shaped leaves.
- Can be pruned to maintain form.
Sources:
Boxwoods: Now You See Them, Soon You Won’t! — Plant & Pest Advisory (rutgers.edu)
Boxwood: Identify and Manage Common Problems | University of Maryland Extension (umd.edu)
Alternatives to Boxwood | CALS (cornell.edu)