Verticillium Wilt

Verticillium wilt is often confused with fusarium wilt due to their similar plant responses.  Treatment for one can apply to the other.

Disease Identification

Description

Verticillium wilt (along with fusarium wilt) is a major disease of a number of garden plants.  It is a soil-borne disease that enters the plant through the root system and spreads through the vascular tissue.  Once inside, it begins blocking the flow of water to various parts of the plant starting with the older leaves.  It will gradually move through the plant as long as the conditions remain favorable.

Verticillium wilt is mainly found in more northern parts of the country (including the Philadelphia suburbs) where the air and soil temperatures remain cooler later into spring.  In Delaware county, verticillium wilt takes a backseat to fusarium wilt which thrives in the mid to late summer when the soil and air temperatures are higher.

Signs of a plant infected with verticillium and fusarium wilt are similar.  The oldest leaves on the plant begin turning yellow and wilting.  As the season progresses, the disease will move to younger leaves resulting in stunted plant growth and fruit production.  Properly established and strong plants will likely outgrow the progress of the disease while weakened and underdeveloped plants will perish.

Many confuse signs of verticillium wilt with late blight.  The easiest way to differentiate the two is late blight results in brown spots on the tomatoes while verticillium wilt doesn’t.  There have not been any documented cases of light blight at Rose Tree Garden.  If you think you have spotted late blight, contact us immediately.

  • Leaves: The bottom leaves turn yellow and then brown as the disease progresses up the plant.
  • Stems: Yellowing may appear on the surface.  Inside a cut stem will contain yellow streaks.
  • Fruit: Not affected

Images

Tomatoes

Beginning in the late spring to early summer, leaves at the bottom of the plant will turn brown.  The browning will work its way up the plant as the season progresses.

Affected Plants

Disease Control

Life Cycle

Verticillium wilt can be introduced into gardens via contaminated seeds or soil.  Because Rose Tree Garden already contains the fungus, there isn’t any concern spreading it to the garden, but be sure to clean and sanitize tools before using them elsewhere.  Once the area has been contaminated, it is difficult to completely eradicate it, so management is the only option.

The verticillium fungus is a soil-borne pathogen that attacks plants through being absorbed by their root systems.  Once inside the plant, the fungus limits the movement of water within the vascular system.  This lack of water slowly kills the plant starting with older leaves and working its way to the younger leaves.  All while this is happening, the concentration of the fungus is increasing in the soil.  Each subsequent planting of vulnerable plants further increases the concentration in the soil along with the amount of the fungus taken in by the plants roots.

Verticillium wilt favors the cool and moist soils found in the spring and early summer.  Vunerable plants in the ground at this time may show signs of the disease soon after being transplanted into the garden. 

High concentrations of the fungus will remain in the soil as long as host plants are regularly planted.

Management

The management recommendations below will help limit the impact of verticillium wilt on your plants.

  1. Plant Rotation: Because verticillium is a soil-borne disease that requires a host to survive, the simplest way to manage the fungus is to practice crop rotation.  A general rule of thumb is to grow plants in areas that have not hosted a similar plant in the past 3 years.  For example, if you grew tomatoes in one part of your garden, do not grow them in that same spot for the next 3 years.  Many gardeners divide their plots into 3 or more sections and plant different crops in each every year.
  2. Resistant Varieties: Many plant varieties have been bred to resist verticillium wilt and should be investigated if you’ve experienced verticillium wilt in your garden.  Before purchasing a plant or seeds look for a “V” on the tag or packet, respectively.  This will indicate the plant shows some resistance to the fungus and may provide an increased level of protection.  Some labels indicate resistance to a specific race of verticillium indicated with a number (i.e. V1, V2, or V3).  It is unlikely you know the specific race of verticillium in your plot, so choosing one with more numbers will offer a wider degree of protection.  Don’t rely solely on these bred varieties because resistance does not mean immunity.
  3. Grafted Varieties: Some varieties of plants have been bred to be extremely resistant to verticillium wilt but do not produce fruit worth eating.  On the other hand, varieties have been bred to be extremely good producers of fruit but are poor at resisting disease.  So with grafting, growers will take the top of the tasty variety and attach it to the bottom of the resistant variety.  This is called a grafted plant.  These have become more popular and are starting to become available in local garden centers.  Some members of Rose Tree Garden graft their own plants and occasionally have extras to share.  When planting, be sure to keep the graft a few inches above the soil line.
  4. Healthy Starts and Transplants: Health of your transplants can go a long way in determining if your plant will survive through the season.  Only purchasing healthy and vigorous plants that do not show signs of stress will give you the best chance of a reasonable harvest at the end of the season.  We highly recommend only purchasing plants from reputable garden centers.

Verticillium wilt cannot be slowed or stopped through topical sprays and soil treatments.  Do not spray anything on your plant or dump products into your soil in an attempt to control the fungus.  At best you will waste your money and at worst you will kill your plant and beneficial insects.