Comparison of 'Pioneer Mac' and 'McIntosh' apples'

A planting was established to compare 'Pioneer Mac,' 'Marshall McIntosh,' a nd 'Rogers Red McIntosh' apple trees. After eight growing seasons, 'Pioneer ' trees were the largest. Cumulative yield per tree was greatest for 'Pione er' and least for 'Marshall', with 'Rogers' intermediate; however, cultivar differences were significant in only one of the six fruiting years. Cumula tive yield efficiency was not affected by cultivar, nor was average crop lo ad. Average fruit weight was greatest for 'Rogers,' with 'Marshall' and 'Pi oneer' similar and significantly less. 'Marshall' fruit developed red color over a larger percentage of the surface than the other two cultivars. Ripe ning, as measured by internal ethylene levels, was earliest for 'Marshall' in two of four years, but in all years, 'Pioneer' and 'Rogers' ripened simi larly. Fruit abscission was earliest from 'Marshall' trees in both years of assessment. In one year, 'Pioneer' fruit dropped later than 'Marshall' but similarly to 'Rogers; and in the second year, 'Pioneer' fruit dropped simi larly to 'Marshall: These data suggest that 'Pioneer Mac' provides no expan sion of the 'McIntosh' harvest season.