Effect of Fenarimol Application Timing on Fruit Shape of Bartlett Pear

Plots were established at Ukiah and Davis, California, and Medford and Hood River, Oregon, to evaluate the effect of fenarimol (Rubigan 1 EC), applied at various stages of bloom development, on fruit shape of Bartlett pear. At each location, 10 different treatment schedules were applied at various combinations of bud burst (BB), green cluster (GC), white bud (WB), and full bloom (FB). In schedules that included an application at FB, the fruit length:diameter (L/D) ratio was significantly reduced in at least three of four locations when compared to untreated controls. When fenarimol was applied at BB, GC, WB, and FB, the L/D ratio was reduced at all locations. Treatment at BB only did not affect L/D ratio. Schedules involving GC or WB, but not FB, resulted in reduced L/D ratios at only one or two locations. When data from all four locations were combined, L/D ratios were significantly reduced by all fenarimol treatments except BB alone, and the smallest L/D ratios resulted from treatments which included applications at both WB and FB. Fruit stem length was significantly reduced by all timings of fenarimol application except GC at Medford, and all timings except BB and GC at Ukiah. Fruit weight did not differ among treatments.