Vascular diseases attack the tissue that conducts water, sugars and mineral nutrients through the trunk and branches of the tree, impeding the tree's ability to receive the products that it needs for growth. According to Ron Smith, a horticulturist with the North Dakota State University Extension Service, poplar trees are prone to problems, including a vascular disease known as Verticillium wilt that affects some species. Verticillium wilt will eventually kill a tree.
A fungus known as Verticillium causes vascular disease in a species of tree known as tulip poplar, or tuliptree. Verticillium occurs in the soil and may survive for years without a host tree. The fungus afflicts more than 300 plant species, according to the University of Kentucky College of Agriculture, and invades plants primarily through wounds in the roots caused by growth or other organisms in the soil, although it may occasionally enter the tree through wounds in the bark as well.
Vascular disease in tulip poplars causes leaves to wilt and branches to die. Branches may begin dying on only one side of the tree or throughout the entire tree, according to the University of Kentucky. Cutting into the sapwood may reveal green, brown or black streaky discoloration, although even wilted branches may not show this discoloration. A definitive diagnosis of Verticillium infection requires testing by a plant pathologist. Contact your local extension office for more information on obtaining this test.
Although tulip poplars are highly susceptible to Verticillium, these trees are only distantly related to true poplar trees, according to George A. Petrides in the Peterson field guide "Eastern Trees." The University of Minnesota Extension states that true poplar trees resist infection by Verticillium, making them ideal trees to plant in an area where the fungus is known to be a problem.
Although Verticillium wilt is fatal to many trees, you may be able to control early infections. Removed all dead or wilted branches, and provide the tree with adequate water and fertilizer, since infections often worsen under water stress. Badly diseased trees should be removed.
Because Verticillium can endure for years in the soil, even without a host, only plant trees known to be resistant in areas where the infection has occurred in the past. Aside from the tulip poplar, other poplars may also resist Verticillium wilt. Also, remove dead branches and do not use chipped wood from infected trees, since mulch, unless it has been properly heated in a compost pile, may spread the infection to other trees.