Received for publication Oct. 5, 1981. Michigan Agricultural Experiment Station Journal Article No. 10189. The cooperation of John Nelson, Research Director of the Michigan Blueberry Growers Association is gratefully acknowledged. This research was supported by U.S.D.A. Special Grant 7503G. Mark Waylon, Don Ramsdell and two anonymous reviewers made useful suggestions on earlier drafts of the manuscript.
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Assistant Professor, Graduate Assistants and Research Technologist, respectively.