The bay tree (Laurus nobilis) is a native of the Mediterranean region and also is referred to as Roman bay and Greek bay. An evergreen, the bay tree is grown as a shrub or specimen plant. Bay tree leaves are used as an herb. A fungal disease causes wilting and browning tree foliage.
Bay trees are susceptible to Dutch elm disease, a common disorder of shade and ornamental trees. The disease is caused by Ophiostoma ulmi fungus that is transmitted to trees by bark beetles. Though more frequent in elm trees, the fungus has a wide host range, including bay.
The disease spreads within the water-conducting tree tissues. Initial symptoms include curling, wilting and yellowing foliage that eventually turns brown. The damage starts in the upper area of the tree and progresses downward. Branches start to wilt, and there are streaks on bark and sapwood. Brown foliage remains attached to the tree.
Irrigate trees well during periods of high heat. Plant resistant tree species. In case of light damage, prune and remove all infected tree areas to about 10 feet of non-infected wood. Bury or burn infected pruned tree areas.