1Received for publication Oct. 31, 1981. Paper No. 8035 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N.C.
The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.
2Graduate student, Associate Professor, and Professor, respectively.
3The assistance of L. R. Grand and R. D. Milholland, Department of Plant Pathology, is also gratefully acknowledged.
