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Beginner

Scientific Name 
Verticillium albo-atrum, Verticillium dahliae

Identification

• In peppers, Verticillium wilt typically begins with wilting
• If severe, leaf yellowing occurs, starting with the older leaves
• Eventually necrotic areas develop, starting at the leaf tips and edges, progressing to leaf drop

Often Confused With
Phytophthora blight
White mould (Sclerotinia)

Period of Activity
Verticillium is a soil-borne disease.  Symptoms are often more severe after fruit set or during dry periods.  The presence of plant parasitic nematodes may further aggravate Verticillium wilt.

Scouting Notes
Soil samples can be taken to test for Verticillium and nematodes.  The best times to sample are in May/June and September/October.  Try to sample at the same time of year each time, using the same laboratory, so that you can compare the counts from year to year.  Counts will be lower in the spring than in the fall.

Thresholds

THRESHOLDS FOR VERTICILLIUM AND NEMATODE COUNTS BASED ON SPRING SAMPLING

ECONOMIC DAMAGE PREDICTED IF:

2,000 or more root-lesion nematodes/kg of soil

1,000 or more root-knot nematodes/kg of soil

12 or more Verticillium dahliae colonies/g of soil

200 or more root-lesion nematodes/kg of soil AND 6 or more Verticillium dahliae colonies/g of soil

100 or more root-knot nematodes/kg of soil AND 6 or more Verticillium dahliae colonies/g of soil

Advanced

Scientific Name 
Verticillium albo-atrum, Verticillium dahliae

Identification
In the early stages, some wilting occurs and plants may become stunted.  Wilted plants may recover at night, or when moisture is plentiful.  Lower leaves may turn yellow and drop off as the disease progresses up the plant.  Eventually necrotic areas develop, starting at the leaf tips and edges, progressing to leaf drop.  A darkening of the vascular tissue may be observed if the stem is split lengthwise near the soil line.

Often Confused With
Phytophthora blight
White mould (Sclerotinia)

Biology
This is a soil-borne disease which can survive in the soil for long periods of time without host plants present.

Period of Activity
Symptoms can occur all season, but are generally more severe after fruit set or during dry spells.  Soil temperatures of 15- 21°C (59- 70°F) and air temperatures of 20- 24°C (68- 75°F) promote the development of symptoms.  The disease is more severe where plant parasitic nematodes are present.

Scouting Notes
Soil samples can be taken to test for Verticillium and nematodes.  The best times to sample are in May/June and September/October.  Try to sample at the same time of year each time, using the same laboratory, so that you can compare the counts from year to year.  Counts will be lower in the spring than in the fall.

Thresholds

THRESHOLDS FOR VERTICILLIUM AND NEMATODE COUNTS BASED ON SPRING SAMPLING

ECONOMIC DAMAGE PREDICTED IF:

2,000 or more root-lesion nematodes/kg of soil

1,000 or more root-knot nematodes/kg of soil

12 or more Verticillium dahliae colonies/g of soil

200 or more root-lesion nematodes/kg of soil AND 6 or more Verticillium dahliae colonies/g of soil

100 or more root-knot nematodes/kg of soil AND 6 or more Verticillium dahliae colonies/g of soil

Management Notes

• Follow a 4- 6 year crop rotation to reduce pathogen populations.
• Do not rotate with related (solanaceous) crops, strawberries or raspberries.
• Keep fields clean of host weeds such as nightshades.
• Cultivars vary in tolerance to Verticillium wilt.
• Soil fumigation may be required if Verticillium and nematode counts are high and yield loss is significant.