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Ecology and Epidemiology

Effects of Certain Solutes, Osmotic Potential, and Soil Solutions on Parasitism of Criconemella xenoplax by Hirsutella rhossiliensis. B. A. Jaffee, Visiting assistant professor, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29632; E. I. Zehr, professor, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29632. Phytopathology 73:544-546. Accepted for publication 3 November 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-544.

Adult Criconemella xenoplax nematodes were inoculated with spores of the fungus, Hirsutella rhossiliensis, and incubated for 5 days in distilled water or in solutions adjusted to osmotic potentials of - 0.3, - 3, or - 6 bars with KCl. Almost all nematodes in KCl solutions became infected, whereas those in distilled water did not. The effect of KCl was not due to the osmotic potential of the incubation solution because little or no infection occurred in solutions adjusted to - 0.3, - 3, or - 6 bars with sucrose or polyethylene glycol 8000. All inoculated nematodes incubated in solutions adjusted to - 6 bars with KCl, KNO₃, KH₂PO₄, CaCl₂, Ca(NO₃)₂, and MgCl₂ became infected; much less infection occurred in solutions containing either Na⁴ or SO₄^-2 (NaCl, NaNO₃, Na₂SO₄, K₂SO₄, and MgSO₄). Infection in extracts of saturated soil from five orchards was correlated with salt concentration as measured by electrical conductivity. Concentration or dilution of the soil extracts increased or decreased infection, respectively. The results indicate that parasitism of C. xenoplax by H. rhossiliensis is greatly influenced by the kind and concentration of ionic solutes in the ambient solution.