Density independent propagation of the entomophagous and mycetophagous nematode, Contortylenchus genitalicola (Tylenchida: Allantonematidae), within the Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae)

摘要

The entomophagous and mycetophagous nematode, Contortylenchus genitalicola, is a candidate biological control agent of the Japanese pine sawyer, Monochamus alternatus, a serious forest pest. In the present study, the propagational traits of C. genitalicola within M. alternatus adults were investigated by counting the numbers of nematode females and progenies (juveniles and eggs) in the adult hosts and weighing host pupae as the host body size. Propagation of C. genitalicola within M. alternatus adults was not affected by the host sex and body size. The total number of nematode progenies within hosts increased with the number of female nematodes, whereas the mean number of nematode progenies per female nematode did not decreased with the increased number of female nematodes within hosts. This indicates that the propagation of C. genitalicola in M. alternatus is density independent. The density independent propagation is considered advantageous for the biological control of M. alternatus using C. genitalicola because this may cause larger production of the infective stages of nematodes for subsequent infection than the density dependent, and is one of the factors to limit host density under the carrying capacity in a theoretical model.