Population cycles of the small moth-borers of sugar cane, Diatraea spp., and their primary and secondary parasitoids, in Trinidad, West Indies

Abstract

Population data consisting of counts of larvae of three species of sugar cane moth-borer, Diatraea spp., and assessments of the extent of parasitism by Paratheresia claripalpis and secondary parasitism by Trichopria cubensis, have been analysed. Time-series analysis of the data revealed two regular cycles in population density, one with a period of about four months, the other with a period of about one year.

The four month cycle was apparent in all three species of Diatraea, although two species, D. saccharalis and D. impersonatella, were subject to parasitism and one, D. centrella, was not. Analysis of the annual cycle of the Diatraea-Paratheresia-Trichopria interaction indicated that the densities of these populations increased during the rainy season and decreased during the dry season.

From the time-series analysis, estimates of time-lags in host-parasitoid interaction responses and in the responses of parasitoid populations' growth rates to changes in their host populations' densities were made. Estimates of parasitoids' generation times could then be derived. These estimates have been compared with independent data collected from direct observations.