Control of Apple Scab and Cytospora Canker with Paclobutrazol    (View PDF)

Gary Watson and Karel Jacobs

Abstract: Forty Malus ‘Radiant’ crabapples, a variety known to be highly susceptible to apple scab disease, were field-planted then treated three months later with paclobutrazol (PBZ) as a basal drench, at rates of 0, 0.8, 1.6, and 2.4 g a.i./cm caliper. Apple scab was significantly reduced for two years post treatment by all rates of PBZ applied. However, significant growth regulation occurred through the third and final year of the study. Thirty Picea pungens (Colorado spruce) trees in containers were treated with PBZ, applied as a basal drench, at rates of 0, 1.6, and 3.2 g a.i./cm caliper. Cytospora canker development from subsequent branch inoculations was significantly reduced by both PBZ treatment rates and persisted through the end of the two year monitoring period. Cytospora canker disease control with only moderate growth regulation indicates that a PBZ basal drench could be developed into a viable landscape treatment.

Keywords: Colorado Spruce; Crabapple; Disease Control; Growth Regulation; Paclobutrazol; Picea pungens.

https://doi.org/10.48044/jauf.2012.017