This Summer, my hedge is dying. It started on one side and continued all the way around. It is pretty much died. I first thought it’s because it needs water so I diligently watered it every other day but it did not stop the hedge from turning brown. All leaves have vanished and the branches are dry. I read that it needs to be trimmed to the stem and may be it will grow back. Is this true? This problem seems very common this summer in South Oakville. Bugs are eating the leaves. I can tell from looking at neighbours’ boxwood shrubs.
Thank you for contacting the Toronto Master Gardeners about your boxwood (Buxus spp.). I can’t be certain without a photo but the damage you have described sounds very much like your hedge has been attacked by Box Tree Moths (BTM), Cydalima perspectalis (Walker). This pest is believed to have originated in Asia and was first detected in Canada in an urban neighbourhood in Toronto in August 2018. It has now reached plague proportions. Symptoms of the presence of BTM are loss of leaves (which are eaten by the larvae), damaged bark (also eaten by larvae) and webbing (spun by the larvae). Positive identification is made by seeing BTM in one of its four life stages (eggs, larvae, pupae, moths). There are good descriptions and photos of these life stages in the link below.
Depending on the extent of the damage to your plants, they may be salvageable but they need to be treated to get rid of this pest before they can start to return to good health. BTM does not attack the boxwood roots, but if left untreated the larvae will consume 100% of the leaves and then start on the bark and stems which will eventually kill the plant.
In addition to helpful information about identifying and treating BTM and how to remove and dispose of infected plants (not in your compost!), the link below also has information about other possible problems with boxwood and alternatives for consideration if your plants need to be replaced.
Good luck with your boxwood hedge!