I have 16 mature boxwoods planted along the fence (facing east and north). 3 out of 16 plants look very very unhealthy. These 3 are located in sunny spot ( the rest are in more shady area, and some also show the signs of the same problem) The leaves on these 3 sick plants are almost gone. it seems something is eating them up. After closer inspection I found lots of white looking webs between the branches and some creatures which look like caterpillars.
Can you please advise how to address this problem to save my plants?
Thanks for contacting the Toronto Master Gardeners.
You must be quite dismayed to find such a sudden decimating of the leaves on some of your boxwoods, with the remaining ones at risk also.
We recently answered a very similar question (see link below) where the person making the query had identified the culprit as the Boxwood Tree Moth. It is hard to be certain from your picture that you also have the same caterpillar (a close-up photo of the caterpillar(s) might have been helpful in narrowing it down). However, this is the most likely culprit as it is a caterpillar that only eats boxwood tree leaves for food, and completely consumes entire swaths of the tree, leading to its demise. Please have a look at the post, which may help you define the problem.
If you determine that the pest is not the Boxwood Tree Moth, the post nevertheless will likely help you in treating the issue, as the advice in our answer and in the referenced articles and websites would be similar for other caterpillars. However, if you need further help, please post again (but note that we are unable to recommend specific pest control products).
Good luck; I really hope you are able to save the boxwoods.