INFLUENCE OF GROUND COVER ON DEVELOPMENT OF PHYTOPHTHORA CROWN AND ROOT ROT OF APPLE TREES

The influence of ground cover with fall rye, perennial rye grass, oats, canola, quack grass, and timothy grass on percent mortality and disease severity ratings of phytophthora crown and root rot of apple trees was determined over five years under orchard conditions in the Okanagan Valley of British Columbia. Fall rye and perennial rye grass significantly (P = 0.05) reduced the disease compared with the hand-weeded control. There were no significant differences in the percent tree mortality among the timothy grass, quack grass, oats, canola, and the hand-weeded control treatments. These results indicate that use of fall rye or perennial rye grass as a ground cover will reduce the incidence of phytophthora crown and root rot of apple trees planted in sandy soils of nurseries or orchards where the disease is present and conditions are sufficiently wet.