Boxwood Pest - Knowledgebase Question

bethesda, MD
Avatar for gcahn6
Question by gcahn6
August 26, 1999
I live in the Washington, DC area and have 8 extremely large mature boxwoods all planted in a row. They are 30 years old and 10 feet in diameter.

Two of them have big chunks of folliage that is dying, i.e. discoloring (red, yellow) and then eventually turning brown and dead. The rest of the plant is find, but there is chunk (2 feet in diameter) of the plant that has died.

This began to happen last year. I thought it might be leaf spot or the boxwood miner. So I made 3 combination sprays a month a part in the spring. The sprays consisted of daconil (to deal with the leaf spot) and cygon (to deal with the leaf miner.)

None of that worked. After 4 months, a chunk of the boxwood had died. So I pruned the dead part away.

Now this year, another chunk of the same plant is infected.

The pH of the soil is 7.0 and I have kept the plants fertilized and watered.

The remaining boxwoods are all fine.

Any ideas what this might be?

Answer from NGA
August 26, 1999
In addition to the two pests you mentioned, the boxwood mite is also fairly common and of the three it is the one more likely to cause bronzing of the foliage -- although I don't think I would call it red. Virginia Cooperative Extension provides some good boxwood information here (Boxwood in the Landscape) and some more specifics on boxwood pests here including photos. Unfortunately, based on your description I can't make a diagnosis of the particular problem you are seeing.

It is important to first specifically indentify the pest and then determine not only which control to use but also the correct timing to use it. Some insects can only be controlled by spraying at a specific time in their life cycle and in many cases two carefully timed applications are needed in order to kill not only the intitial generation of adults but also the remaining generation that hatches later. You might wish to contact your local County Extension (301-590-9638) to see if they can help you identify the pest and suggest the appropriate control measures for it.

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