Geographical variation of Delphacodes kuscheli (Fennah) population abundance in central Argentina

Abstract

Delphacodes kuscheli is the vector of the Río Cuarto Corn Disease, which affects maize in central Argentina. This disease is endemic of Río Cuarto Department in Córdoba Province. Preliminary studies indicate that the insect is present in Córdoba, La Pampa, San Luis, Santa Fe and Buenos Aires provinces, but there are few studies on the abundance in these places. Previous research showed that Delphacodes kuscheli arrives to maize plots from distant sources, and that there is a difference in the abundance of Delphacodes kuscheli in the endemic area and outside it. In this work we study the geographic variations of the population abundance of Delphacodes kuscheli along a transect that crosses the endemic area to verify whether there is a difference between the vector population dynamics within and outside the endemic area. Samples of dispersing individual were collected during three years by using sticky traps at two different heights. The samples were taken in eight sampling sites between the localities of Manfredi (Córdoba) and Mercedes (San Luis). Dispersive individuals of Delphacodes kuscheli were more abundant in the endemic area than outside it. The dispersive population captured with low traps had a higher proportion of females, but there were no differences at high traps. The correlation of density changes observed in high traps decreased with distance between sampling sites, but there was no relationship for low traps. It is discussed how these results could indicate that Delphacodes kuscheli is a species highly adapted to live in unstable habitats.