Mahaleb is the most susceptible cherry rootstock, whereas Mazzard, Morello, and Colt are somewhat more resistant and would be recommended on the heavier cherry soils. Some of the newer clonal cherry rootstocks may have an additional measure of resistance, but these have not yet been sufficiently evaluated to determine. Seedling peach and apricot rootstocks are very susceptible, although the range of suitable soils may be expanded if these trees can be grown without other problems on plum-type rootstocks. Soil fumigation before planting is ineffective in controlling Phytophthora root and crown rots because the fumigant never completely eradicates existing inoculum from the soil and Phytophthora spp. New fungicides have recently been developed which are effective in controlling these diseases when used preventively, but they are seldom effective in reviving trees once the crown has become infected and moderate symptoms of decline have appeared.
Fungicides are most effective when used in combination with the cultural practices described above.
Check current labels and recommendations for approved materials and timings.