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Raspberries: Phytophthora Root Rot

Phytophthora Root Rot (Phytophthora spp.) – is a common cause of wilting in red raspberries. It mostly occurs in heavy soils, where standing water occurs, or where plants have been heavily mulched.

Raspberry planting with large pools of water in-between rows where soil is below water line. Most raspberry plants in row are healthy, but a large gap exists in a row where plants appear to be missing. The gap is bordered by a shrunken or dwarfed raspberry plant.

Raspberry planting with alternating patches of green, fruiting canes and brown, dead canes.

Canes suddenly wilt and turn brown at the onset of warm temperatures, usually in June.

Close-up of raspberry planting with green stalks and wilted, brown leaves. Few green leaves remain, most of the foliage along the length of the stalk looks brown and droopy.
Onset of root rot in June.

Field diagnosis involves removing the outer layer of epidermis on the roots and canes. Phytophthora infection is usually expressed as a chocolate-brown coloration of roots with a sharp transition to white, uninfected wood within the roots or crown.

Close-up of raspberry root ball. The thickest, central roots have the skin scraped off of towards the top of the root mass. The peeled area has a pale, beige patch at the top, that sharply transitions to woody brown.

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Use these resources if you need additional help with diagnosis and to find solutions to your problem.