Predicting population level of Delphacodes kuscheli, vector of Mal de Río Cuarto virus, and climate risk in the Argentine Pampas using meteorological models.

Abstract

The planthopper Delphacodes kuscheli Fennah (Hemiptera: Delphacidae), principal insect vector of Mal de Rio Cuarto virus on corn in Argentina, produces severe disease outbreaks when migration of large macropterous populations coincides with early corn growth stages. Linear models based on winter environmental variables were developed to explain variation of macropterous populations accumulated on oat until November 30 (1993-2001) in La Aguada (department of Rio Cuarto, Cordoba, Argentina). Using daily records of maximum and minimum temperatures and precipitation, variables were generated and processed in different periods from June 1 to September 20. The best bivariate model (R2=0.97) had the lowest mean square error, was selected by Stepwise procedure, and its validation was highly satisfactory. It included the variable DDTxn, which accumulates mean temperature values exceeding 10°C on days with maximum and minimum temperature >24.5°C and 11°C, respectively, and DPr, which counts days with precipitation (>0mm). These variables were processed from July 1 to September 19. Using this model (correctly validated against independent observations in Chajan, Sol de Mayo and Espinillo -department of Rio Cuarto- for 2, 3 and 7 years, respectively), climate risk in the Pampas region was evaluated relative to insect population levels in the endemic area.