Pathogenicity and Population Dynamics of Meloidogyne hapla Associated with Allium cepa. A. E. MacGuidwin, Department of Plant Pathology, University of Wisconsin, Madison 53706. G. W. Bird, D. L. Haynes, and S. H. Gage. Department of Entomology, Michigan State University, East Lansing 48823. Plant Dis. 71:446-449. Accepted for publication 11 November 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0446.

Densities of Meloidogyne hapla from 15,000 to 40,000 eggs per plant at seeding retarded the growth of Allium cepa ‘Krummery Special’ under greenhouse conditions. There was a significant (P = 0.05) negative linear relationship between the fresh bulb weight of A. cepa grown in the field and M. hapla density at midseason. M. hapla developed and reproduced on A. cepa in both greenhouse and field environments. The rate of colonization of A. cepa roots and reproduction by M. hapla were not affected by increasing nematode inoculum density. According to field census data, there was one generation of M. hapla associated with A. cepa during the 1981 growing season. The fourfold increase in the M. hapla population level was low compared with that reported on other hosts. This seemed to be related to the early senescence of A. cepa roots relative to the rate of M. hapla development rather than to excessive mortality of M. hapla within root systems.

Keyword(s): northern root-knot nematode, onion.