Why Are My Raspberry Canes Wilting and Turning Brown at the Base?

Raspberry canes that wilt progressively from the base, with the crown area and lower stem turning dark brown and the bark showing a reddish-brown discolouration when scraped, are showing signs of Phytophthora root rot — one of the most destructive raspberry diseases in poorly-drained soils. Unlike cane blight which usually attacks canes at specific points above ground, Phytophthora is a root and crown pathogen that kills from the ground down, affecting the entire root system.

What Phytophthora does to raspberry roots

Phytophthora fragariae var. rubi (and related species) are water moulds that thrive in oxygen-poor, waterlogged soil. They infect the small feeder roots first, causing them to turn brown and die, then progress to the main roots and the crown. As the root system collapses, canes cannot access water or nutrients and wilt progressively. The wilting is non-recoverable — even if the soil subsequently dries, the destroyed root tissue cannot regenerate. In severe cases the entire row can be killed.

Is the row still recoverable?

If only a few plants are affected and the disease is caught early, improving drainage — by raising the bed height, incorporating grit or diverting surface water — combined with removing the worst-affected canes may allow the remainder to continue. However, if more than a third of the row is showing symptoms, and the soil is persistently waterlogged, the row is unlikely to recover productively. Removing all affected material and not replanting raspberries in that spot for five or more years is the pragmatic decision.

Prevention for new plantings

Never plant raspberries in soil that sits waterlogged after rain. Test drainage by digging a hole 30cm deep and filling it with water — if water remains after 30 minutes, drainage is inadequate. Raised beds at least 20cm above the surrounding soil level resolve drainage problems on most sites. Choose varieties described as having tolerance to Phytophthora — these are increasingly available from specialist suppliers.