Boxwoods turning yellow problem at my home

Question: Last year one of our boxwood’s leaves began turning yellowish beige in circular shapes.  It stopped over the winter but over the last two weeks it has begun again and is spreading on the one bush.  Over the last two weeks I have also notices that four other bushed has leaves turning yellowish beige in small circles about 5” in width.  No one seems to know what is happening to our boxwoods.  We have about 27 boxwoods in the front of our house and are worried that whatever this is it will spread to the other boxwoods.  Can you please help me.  I would greatly appreciate it.

responder: An Ask Extension Expert Replied April 30, 2023, 3:02 PM EDT
response: There are several reasons for boxwoods to show yellow/dying leaves. The small yellowed areas on your shrubs don't appear to be from a serious issue. The plant with the large brown area on top is more concerning. Below are some of the most common boxwood problems.  The most common cause for yellowing leaves is winter burn--cold winter winds and weather, ice, and cold. Damage occurs when an unseasonably warm winter day gets the water flowing in the plant — water that quickly freezes when evening arrives. This damages the plant, and as a result, the leaves turn pale yellow.  You can minimize winter damage by erecting some sort of cold wind protection such as burlap wraps around your boxwoods, but considering you have 27 of them, this may not be feasible. A thick layer of mulch around your boxwoods to keep the roots warmer would be a good idea. Feed and water your bushes like normal to help them recover.  Boxwoods are susceptible to pests such as boxwood scale, boxwood sawfly, boxwood moth, and boxwood weevil. Examine your plants for any sign of insect activity. Pest control is essential to prevent the spread of diseases.  A relatively new and serious problem is the fungal disease called boxwood blight. The link below will give you information on this disease and what you can do about it.   https://www.michigan.gov/invasives/id-report/disease/boxwood-blight  Salt used for sidewalks and roadways can cause damage to boxwoods. First, the spray of the salt water on the foliage can cause the plant to desiccate in those tissues, killing the leaves on one side of the plant. Excessive salt washed into the soil can also change the water uptake of the plant, causing salt damage. In these cases, it is most identifiable when there is a pattern where the boxwoods closest to walking surfaces show the worst damage. It is also noticed in spring.  Root rot is another possibility. Boxwoods are very sensitive to excess amounts of water. The roots can be damaged when exposed to too much water, and the bush cannot absorb nutrients from the soil. The best way to solve this problem is to add a layer of sand or peat moss to the ground. This will prevent excess moisture and allow the boxwood to grow healthy.  Another possibility...If you have a dog, or if your neighborhood has roaming dogs, is damage from dog urine. Considering the fact that the yellowed areas are circular and relatively low to the ground make this a definite possibility.  The boxwood leafminer is a serious pest of boxwoods. The tiny orange flies that swarm the plant aren't so much the problem as the eggs they lay, because it's the tiny larvae that feast on the leaves. Leaves infested with leafminer larvae usually present with misshapen, yellow,or brown swollen spots and often drop from the plant. The larval feeding between the upper and lower leaves causes blistering and often discoloration. A severe infestation can defoliate and kill a boxwood.   Boxwoods should be planted in a well-drained area in light, fertile soil. Avoid depressions where water tends to collect. Strong, healthy plants rarely get sick, so keep examine your plants regularly for any sign of damage.   I am unable to diagnose your issue by merely looking at pictures. Since you have so many boxwoods, and they are obviously very valuable to you, your best resource is a certified arborist. An arborist is a certified and generally insured expert in trees and their problems. He or she can examine your boxwoods and make recommendations regarding their health, any needed judicial pruning, and whether or not (in his opinion) any of them should be removed. You can find a certified arborist in your area here:  http://www.treesaregood.org/  Click on "Find an Arborist" at the top of the page; then click on United States from the pull-down menu. Then enter your State and City. This should bring up a list of certified arborists nearest to you. Or you may be able to locate one under "Tree Services" in your local Yellow Pages.

responder: The Question Asker Replied April 30, 2023, 5:28 PM EDT
response: Thank you!!!  Sent from my iPad  On Apr 30, 2023, at 3:02 PM, Ask Extension <<personal data hidden>> wrote:    ﻿