One of the most exciting prospects for reducing pesticide use on apples has been the recent emergence of apple cultivars that are immune to apple scab and also possess desirable horticultural characteristics. Many of these cultivars also have good to excellent resistance to cedar-apple rust and fire blight. Their potential is at least as exciting for home orchardists as for commercial growers. Among the named scab-immune cultivars to come from the Purdue-Rutgers-Illinois (PRI) breeding program over the last few years are Redfree, Jonafree, Liberty, Dayton, and Williams Pride. Two newly named cultivars, Gold Rush and Enterprise, will be released sometime this year. In addition, several numbered selections will receive names within the next few years. The eating quality of some of these new cultivars is first-rate, and many are adapted for prolonged winter storage.
How well will these cultivars perform under Iowa conditions? A few growers have begun experimenting with Redfree, Jonafree, Liberty, and others, but no systematic testing has been done. This spring, Paul Domoto, ISU tree fruit specialist, and I will plant 12 scab-immune cultivars from the PRI program on M.7 EMLA rootstock at several sites around the state. Replicated plantings, including 9 trees of each cultivar as well as trees of two scab-susceptible cultivars (Jonathan and Empire), will be established at the Hort Farm and at ISU's Castana Farm. Nonreplicated plantings will be located as follows: at the Wright Orchard near Hamburg; at Kazimour Orchard near Marion; at John and Mary Ree's orchard near Burt; at ISU's outlying farms at Crawfordsville and Calumet; and at a Master Gardener planting in Des Moines. These plantings will give us a good picture of the adaptability of the new cultivars in all parts of the state. We will be monitoring winter hardiness, yield, and fruit quality, and also develop minimal-pesticide schedules for the plantings at the Hort Farm and Castana.
This is a long-term (10-12 year) project, but we will update you on findings as they develop.
This article originally appeared in the April 14, 1993 issue, p. 46.