Q.? disease i or insect festation on my lilac bushes
I have 3 bushes approx. 10 years old & just noticed on one there is a beige colored area on the trunk of one with a hole in the trunk. What could this be?

I can't determine the cause with just your description.
You can upload an image to our Q & A.
These links may help you pinpoint the issue.
https://www.gardeningknowhow.com/ornamental/shrubs/lilac/common-lilac-problems.htm
https://www.gardeningknowhow.com/ornamental/shrubs/lilac/witches-broom-in-lilacs.htm
https://www.gardeningknowhow.com/ornamental/shrubs/lilac/powdery-mildew-on-lilac-bushes.htm