Populations of T. allius increased to levels nine times higher in Glurk tobacco plants infected with California tobacco rattle virus than in healthy plants of the same variety and age. Populations of T. christiei increased with applications of Hoagland's nutrient solution diluted up to 50-percent concentration, whereas population densities were low at the highest concentration (100 percent), and in water alone. Trichodorus allius did not seem to be affected to a large extent by similar

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... ons of Hoagland's nutrient solution. Soil type influenced populations of T. allius; lighter soils were conducive to development of higher populations while soil, coarse sand, and white quartz sand used separately were not favorable for reproduction. Temperature proved to be one of the most important ecological factors in nematode reproduction. The optimum temperatures for the reproduction of each species was as follows: T. christiei, 16° to 24° C; T. porosus, 24° C; and. T allius, 21° to 24° C. Extremes of temperatures at which the different species could reproduce also varied. Populations of T. christiei were affected by an undetermined disease or condition which seemed to slow movement but did not have any apparent effect on rate of reproduction. Host ranges of three species of Trichodorus were studied. All three nematode species seemed to be polyphagous because 90 percent, 90 percent and 95 percent of the plant species tested were hosts of T. christiei, T. porosus, and T. allius, respectively. Twenty-five plant species were tested for T. porosus, 50 for T. christiei and 38 for T. allius. A method is described for keeping populations of T. allius alive in water for extended periods of time.