Abstract: Experiments were conducted to determine whether responses of strawberry plants topowdery mildew follow a similar trend over time and over clonal propagation. The same plants(including daughter plants) were inoculated over a period of several months. Results suggestedthat correlation in the response of the same plants to mildew over time and over clonalpropagation is weak, only accounting for < 9% of the total observed variability. Seedlings weremost susceptible to mildew; however, new leaves on many of these plants were free of mildewdespite of artificial inoculation a few months later. The ability to differentiate susceptibility ofindividual genotypes to mildew was greatly enhanced if screening was based on even just twodaughter (clonal) plants of the same age. Selection for mildew resistance based on single plant inthe early stages of breeding is thus not likely to be either reliable or efficient.