Bug track, or worm track, or sometimes termed flex, is caused by annual attacks from a small fly and results in orange to reddish to brownish dashes in the wood of White Birch. Similar insects can cause the same in White Ash (Glass Fly), Black Cherry (gum), and Soft Maple.
Bug track is a surface defect only and will not affect any finishing; i.e., paint, stain, oil, etc. other than show the "defect" in a clear finish. The reason that veneer buyers do not like it is that often times they try to substitute White Birch for the more expensive Yellow Birch. The catch is that Yellow Birch is not affected by these insects and consequently never shows any track. Paper Birch veneer logs without the bug track may command a price of $2 / bf whereas the same quality log with the track will only sell for $.80 / bf.
© 2001 by David Mather. All rights reserved. No parts of this publication may be reproduced in any form or by any means without the written permission of the author.