Phytophthora Root Rot Phytophthora Root Rot of raspberries is caused by Phytophthora fragariae var. This disease was first reported on red raspberries in Scotland in 1937. It has been in North America since 1958 and has been a widespread problem since the mid 1980s. It is primarily a red and purple raspberry disease, but can infect black raspberries and blackberries as well. It usually affects plants in wet or heavy soils.
Infection can occur in patches in the planting which correspond to the low or soggy areas.
These patches can become larger with time, as the amount of the fungus in the soil increases. The symptoms are most noticeable in the spring. Both first year and second year canes may be affected. Generally, fewer first year canes are produced than normal. First year canes may develop a dark, watersoaked spot at the base and may then wilt rapidly and collapse.