Every stripe displays worm holes. Wormy Maple - primary insect cause is the Ambrosia beetle. Trees or wood species most affected are aspen, cottonwood, elm, hickory, maples, oaks, pecan, pines, sweetgum, tupelo, and yellow poplar. The stains are oval to slightly elongated with irregular margins. Bruce Hoadley in Understanding Wood defines a burl as, A hard, woody outgrowth on a tree, more or less rounded in form, usually resulting from the entwined growth of a cluster of adventitious buds.
Burls are a source of highly figured veneers.
The most easily recognized external expression of figure in trees is an overgrowth commonly referred to as a burl. Burls are relatively large, abnormal bulges that sometimes form on trunks and limbs of almost any tree species. Burl surfaces may be corrugated or smooth, but usually are somewhat gnarled. Conifer burls generally are corrugated. Fiber alignment within burls, which is extremely irregular, produces a striking figure that is highly prized for veneer and turned articles.