Beginner

Scientific Name
Phytophthora spp.

Identification

• Usually appears only on fruit in contact with the soil
• A dark spot forms on the fruit, enlarging to cover large areas of the fruit, showing concentric light and dark brown rings
• Fruit initially remains firm, but later decays
• If wet conditions persist, a white fungal growth can develop on the fruit

Often Confused With
Late Blight (Similar to late blight fruit symptoms, but the lesions remain smooth.)

Period of Activity
Buckeye rot favours very warm, humid weather and wet conditions. The time for concern is when fruit are present, however the disease is uncommon and not usually a serious concern. 

Scouting Notes
Buckeye rot resembles late blight lesions on fruit, however the surface of fruit affected by buckeye rot remains smooth and foliar symptoms associated with late blight are not present.

Thresholds
None established

Advanced

Scientific Name
Phytophthora spp.

Identification
The disease usually appears only on fruit that contact the soil. A dark spot forms on the fruit, enlarging to cover large areas of the fruit, showing concentric light and dark brown rings. Fruit initially remains firm, but later decays. If wet conditions persist, a white fungal growth can develop on the fruit.

Often Confused With
Late Blight (Similar to late blight fruit symptoms, but the lesions remain smooth.)

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 short crop rotations with susceptible crops (cucurbits, solanaceous crops), the levels of inoculum build up over time, potentially becoming a significant production problem.

Sporangia are formed on the roots, stems and leaves of infected plants. They are spread long distances by air and splashing water. Under saturated conditions, the sporangia will release motile zoospores. The zoospores move on the plant surface and in the soil water. They are capable of directional mobility and 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 an additional source of zoospores.

Period of Activity
Buckeye rot favours very warm, humid weather and wet conditions. The time for concern is when fruit are present, however the disease is uncommon and not usually a serious concern. 

Scouting Notes

• Buckeye rot resembles late blight lesions on fruit, however the surface of fruit affected by buckeye rot remains smooth and foliar symptoms associated with late blight are not present..

Thresholds
None established

Management Notes

• Rotate fields for a minimum of 3 years away from all host crops. 
• Select well-drained fields. Where drainage problems do exist, use a grassed waterway to divert surface water away from the crop. 
• Minimize soil compaction and avoid excessive irrigation, especially in overhead systems.