Effect of Criconemella onoensis on Potato

Criconemella onoensis (Luc) Luc and Raski increased to high (458-1,290/100 cm(3)) soil population densities in four fields planted to cover crops of sorghum-sudangrass (Sorghum bicolor (L.) Moench x S. arundinaceum (Desv.) Stapf var. sudanense (Stapf) Hitchc. 'Funk FP-4') during the summer of 1984 in southeastern Florida. Three pathogenicity tests conducted in the greenhouse with C. onoensis on potato (Solanum tuberosum L. 'La Rouge') using three different methods (inoculation, chemical treatment of infested soil, or pasteurization of infested soil) revealed no significant (P = 0.10) differences in plant growth, despite significant (P = 0.05) differences in population densities of C. onoensis between treated and control pots in each test. In these three tests, the maximum initial density of C. onoensis used was 720/100 cm(3) soil and the maximum final density was 686/100 cm(3) soil. Application of 933 liters/ha of Vapam to a field site with a pretreatment density of 1,120 C. onoensis/100 cm(3) soil significantly (P = 0.05) reduced populations compared with untreated control plots, but yields remained higher in control plots. Apparently C. onoensis has no significant effect on potato growth at the population densities tested.