Ornamental Plants
Annual Reports and Research Reviews
2001

Special Circular 186-02

Apple Scab on Crabapples at the Secrest Arboretum: 2001

Results and Discussion

Apple scab ratings of crabapples at Secrest Arboretum for the 2001 season are presented in Table 1. Following are key findings.

1. A third of the crabapple taxa in the plot exhibited significant defoliation and substantial negative aesthetic effect in 2001 (Table 1).
2. Despite this level of scab pressure, nearly a third of the crabapple taxa in the plot exhibited no apple scab incidence in 2001 (Table 1). Furthermore, nearly half of the crabapples in the plot did not exhibit aesthetic impact from apple scab in 2001. This data, coupled with similar data from previous years, suggests that landscape managers have the option of selecting a wide palette of crabapples with little or no scab problems.
3. For the second year in row, 'Prairifire' crabapple did exhibit some scab in the plot, though it was minor. This is of some concern because scab was not seen on 'Prairifire' for several decades in the current and former plots at Secrest Arboretum. Though the level of scab was minor on 'Prairifire,' its presence in 2000 and 2001 raises the question of whether there is a new race of the apple scab fungus (Venturia inaequalis) in the arboretum.