Discolored, brown and grayish vascular tissue exposed in a limb with Dutch elm disease, Ophiostoma ulmi.

An elm limb cut longitudinally to expose vascular tissue discolored by Dutch elm disease. Credit: William Jacobi, Colorado State University, Bugwood.org
Discolored, brown and grayish vascular tissue exposed in a limb with Dutch elm disease, Ophiostoma ulmi. Credit: William Jacobi, Colorado State University, Bugwood.org