An experiment in which second-stage juveniles of Meloidogyne javanica were extracted after 1, 2, 3 or 4 days in soil containing between 10 3 and 5 x 10 5 Pasteuria penetrans spores/g soil showed that the number of spores attached increased in proportion to both spore concentration and time. The rate of spore attachment at 27°C was approximately double that at 18°C. In a second experiment, M. javanica juveniles were given access to tomato roots through 2, 4 or 8 cm long tubes filled with soil containing 0, 10 3 , 10 4 , 10 5 or 10 6 spores/g soil. Regardless of whether spores were present or not, the number of galls formed on roots decreased as the distance juveniles migrated increased. Gall production was lessened in the presence of P. penetrans and virtually no galls formed when juveniles moved more than 2 cm through soil containing 10 5 spores/g soil. Data from both experiments were used to predict the concentration of P. penetrans spores likely to be needed to control root-knot nematodes in the field.
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Perry et al. (1990) studied this question.