Prospects for integrated control of Phytophthora diseases of strawberry

At least seven Phytophthora species attack strawberry, causing root, crown and fruit rots but the most important are P. cactorum (leather rot of fruit and crown rot) and P. fragariae (red core or red stele root rot). At present these two diseases are largely controlled by the widespread use of the fungicide fosetyl-Al, other fungicides and soil sterilants but more environmentally benign control strategies could and should play a more significant part in reducing their impact. These include cultural control, sensitive diagnostics for testing the health of propagation stocks and host resistance. New diagnostics based on the polymerase chain reaction are sensitive, specific and rapid and can be used on plants, water and soil. Integrated with host resistance, they could greatly lessen the impact of crown rot and red stele. For crown rot, avoiding hyper-susceptible cultivars may be all that is needed for useful control. Resistance to red stele is based on R-genes but in this soilborne disease it is still well worth exploiting, although it is at risk from the lability of races of the pathogen and uncontrolled movement of new races.