Inhibition ofCriconemella xenoplaxEgg Hatch byPseudomonas aureofaciens

Nine fluorescent pseudomonad strains and one strain each of Escherichia coli and Rhizobium fredii were tested for potential to inhibit Criconemella xenoplax egg hatch. One strain, Pseudomonas aureofaciens BG33, and its genetically modified derivative, BG33CL1R, effectively inhibited egg hatch at 2.0 X 10(8) cfu ml-1. Strain BG33CL1R inhibited egg hatch by 5, 50, and 95% when present at 1.0 X 10(7), 4.8 X 10(7), and 2.4 X 10(8) cfu ml-1, respectively. Eggs were sensitive to BG33CL1R from the time of deposition until second-stage juveniles were formed inside eggs 6.5 days later. In contrast, activity of second-stage juveniles and adults did not appear to be affected by incubation in BG33CL1R for up to 2 wk. Seven strains of P. aureofaciens and one strain each of E. coli, P. chlororaphis, and R. fredii did not inhibit egg hatch in similar tests. Therefore, general septic conditions apparently are not responsible for egg kill. The potential for P. aureofaciens BG33 and BG33CL1R to kill C. xenoplax eggs could explain in part their suppression of nematode population increase in greenhouse tests.