Does your tree look like this?

Damage is often patchy.

Have you ever noticed a tree with a branch that turns brown midway through the season while the rest look fine? Or a vegetable plant with stems turning yellow and brown?

What is it?  

Verticillium Wilt (Vw) V. dahliae  and Verticillium albo-atrum  is a soil borne disease that spreads through the roots to a plant’s vascular system. It can stump a gardener with early drought-like symptoms. It is a fatal disease of many important agricultural and horticultural crops. It is particularly present wherever potatoes and mint were farmed. And it can even kill a tree.

What does Verticillium Wilt look like? 

Vw symptoms can include wilt, chlorosis, reddish to purplish discoloration of leaves or stems and brown-stained or stunted leaves and vary widely between species.See video.

Vw on Maple

If you think your plant is infected, first find out whether that species is a host. Plants Resistant Or Susceptible To Verticillium Wilt, developed by the University of California, is a good resource. 
Proper diagnosis requires laboratory testing to rule out other organisms. Homeowners can submit a sample of soil to find out the level of Vw in the soil. The cost is $50.00 for plant material sample and $105.00 for the soil testing at the University of Idaho Plant Disease Diagnostics Lab in Parma, Idaho. Be sure to contact the lab first for specific instructions at (208) 722-6701.

What Types of Plants are susceptible?

Vw affects over 300 species. Trees most commonly and severely affected are maple and ash. The list also includes red-bud, lilac, catalpa, and smoke-bush.

Vw on dahlia

Vw on blackberry

Annuals, including dahlia and sunflower can be infected, as well as garden plants like cantaloupe, tomato, and asparagus. Once affected, roots may not develop normally again.

Dr. James Woodhall, Assistant Professor and Plant Pathologist with the U of I Parma Research Center says Vw is patchy – particularly in maples, but also as it appears throughout your property. Not every inch of ground will have it.

How do I save a tree or shrub with Verticillium wilt?  

Trees and shrubs infected with this systemic disease cannot be cured. They may die quickly in one season or slowly over several years. However, you can extend the life of your plants by making sure that you water and fertilize properly. 

In woody host plants, pruning of symptomatic limbs to remove all discolored sapwood, followed by burning, has prolonged the life expectancy of some trees.

If you remove a plant or tree because of this, be sure to plant a high value tree in some other field. This fungal genus may remain alive in the soil for many years in a resting state.

Can I Prevent Verticillium damage in the future?

The best way to avoid Vw is to plant deciduous trees and shrubs that are immune or resistant. You may have seen some or all of the letters VFNT next to the names of hybrid plant varieties in catalogs and on seed packets. The name will have a V following the variety name if it is resistant to Vw. Always test the soil before planting, especially with high value trees. Purchase disease tolerant trees and plants.

Brian Hudelson, UW-Madison Plant Pathology advises not to use mulches that may have been produced from infected trees or have unknown composition. Finally, immediately collect and discard leaves that have fallen from symptomatic trees.  Both mulch and leaves are potential sources of Verticillium.