The Effect of Soil Type on Movement and Infection Rate of Larvae of Tylenchulus semipenetrans.

Most of the Tylenchulus semipenetrans larvae applied on the surface of four soils in pots 14.5-cm deep moved no further downward than 6.5 crn, and remained in the upper half of the pot. The percentage of second-stage larvae that developed into adult females on 'Homosassa' sweet orange in the soils were: sandy loam, 6.8% in the same soil with inoculation holes, 8.6%; loamy sand, 5.4%; coarse sand, 0.2%; and in sand-peat (2:1, v/v)mixture 0.04%. Low percentage infection in coarse sand and sand-peat mixture may have been caused by restriction of larval migration in the coarse sand, and by low pH or toxic organic acids in the sand-peat mixture. Good root development occurred throughout all soils.