In vitro occurrence of dispersal fourth stage juveniles in Bursaphelenchus xylophilus co-incubated with Monochamus alternatus

The pinewood nematode (PWN), Bursaphelenchus xylophilus, was cultured on an unidentified fungus, which was related to Contortylenchus genitalicola, grown on potatoglucose-agar medium supplemented with yeast extract in a flattened culture bottle. C. genitalicola is an entomophagous and mycetophagous nematode parasitic to the Japanese pine sawyer, Monochamus alternatus. The mean number of dispersal 3rd stage juveniles (DSJ3s) and the mean percentage of DSJ3 in the populations of PWN were 24, 870 and 93.1% at 80 days' culture. Dispersal 4th stage juveniles (DSJ4s) developed in the culture bottles when B. xylophilus were co-incubated with pupa or adult M. alternatus on the fungus. DSJ4s (mean number, 9, 105) were recovered from 9-day-oldM. alternatusadults that had been coincubated with B. xylophilus during the pupal and adult stages. The usual theory that occurrence of DSJ4 is triggered mainly by existence of Monochamus cerambycid pupa and adult has been supported by the in vitro experiment. Jpn. J. Nematol. 32 (2), 53-59 (2002).