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Beginner

Scientific Name 
Phytophthora capsici

Identification

• This pathogen can initially cause a root and crown rot of pepper, which leads to wilting and death of the entire plant
• Above-ground infections cause stem and leaf lesions which are first dark green and water-soaked, then later become dry and turn purplish-brown
• Fruit may develop water-soaked patches that shrivel and darken
• A white to greyish mould may appear on the lesion or inside the fruit
• A brown discolouration of the vascular tissue can be seen if the main stem is cut open

Often Confused With
Verticillium wilt
White mold (Sclerotinia)

Period of Activity
Phytophthora spreads rapidly during warm, wet weather. Phytophthora problems often follow field drainage patterns.

Scouting Notes
Early diagnosis will allow growers to manage Phytophthora through crop rotation, before the inoculum builds to potentially devastating levels.

Thresholds
None established.

Advanced

Scientific Name 
Phytophthora capsici

While Phytophthora has not been a significant problem in peppers in Ontario in the past, this disease has caused serious losses in Michigan, Illinois and New York.  Once established in a field, Phytophthora is extremely difficult to control.

Identification
Depending on the crop affected and time of infection, Phytophthora symptoms include crown rot, foliar blight, fruit rot and stunting. 

This pathogen can initially cause a root and crown rot of pepper, which leads to wilting and death of the entire plant.  Above-ground infections cause stem and leaf lesions.  Stem lesions are first dark green and water soaked, then later become dry and turn purplish-brown.  Typically, the part of the plant above the affected area wilts.  Irregular water-soaked lesions may appear on the leaves, later drying to a tan colour or appearing bleached.  Fruit may develop water-soaked patches that shrivel and darken.  A white to greyish mould may appear on the lesion or inside the fruit.  Fruit typically shrivel, but remain attached to the plant.  A brown discolouration of the vascular tissue can be seen if the main stem is cut open.

Often Confused With
Verticillium wilt
White mold (Sclerotinia)

Biology
Phytophthora survives between crops as a thick-walled oospore or as mycelium on crop residue.  The oospores can survive in the soil for five to ten years.  Under intensive solanaceous and cucurbit production and short crop rotations, the levels of inoculum build up over time, potentially becoming a significant production problem.

Spores are formed on the roots, stems and leaves of infected plants.  They are spread long distances by air and splashing water.  Under saturated conditions, zoospores that can move on the plant surface and in the soil water are released.  They are attracted by the root exudates of host crops, allowing the infection to spread from plant to plant, and from field to field.  Irrigation water may also be a source of zoospores.

Period of Activity
Phytophthora spreads rapidly during warm, wet weather.  Ideal conditions for infection are moist soils above 18°C (65° F) and air temperatures of 24- 29°C (75- 85° F).
Phytophthora problems often follow field drainage patterns.  They are most likely to occur in low lying, or poorly drained areas of the field. 

Scouting Notes
Early diagnosis will allow growers to manage it through crop rotation, before the inoculum builds to potentially devastating levels.

Thresholds
None established.

Management Notes

• Rotate fields for a minimum of three years away from all host crops.
• Do not plant peppers in a field that has a history of Phytophthora infections. 
• Select well-drained fields. 
• Where drainage problems do exist, use a grassed waterway to divert surface water away from the crop.
• Plant resistant varieties if possible.  Some pepper varieties have tolerance to foliar or root infections.
• Minimize soil compaction and avoid excessive irrigation, especially in overhead systems.
• Raised beds and the use of plastic mulch can significantly reduce Phytophthora capsici infections in peppers.  Beds must be dome-shaped. 
• Ensure that the planter does not leave a depression at the base of the plants.
• Clean farm equipment if traveling between infected and non-infected fields.