CONICET | Buscador de Institutos y Recursos Humanos

The effect of host patch area and configuration on the abundance of dispersing individuals of Delphacodes kuscheli Fennah (Homoptera: Delphacidae), the vector of Río Cuarto disease in maize, was investigated in the main maize production area of Argentina. Actively dispersing D. kuscheli individuals were collected from 15 sampling sites during the spring seasons of 1999 and 2000, using sticky traps placed at 6 m above ground level. Host patches were detected and quantified using Landsat 5 TM images for the periods studied. FRAGSTATS 3.3 was used to estimate the Total Class Area, Largest Patch Index, Mean Proximity Index and Patch Cohesion Index for patches of winter pastures (the main insect host during winter) as observed from the satellite images. Landsat 5 TM estimations showed local variability in the proportion of winter pastures,, with patches bigger during 1999 than during 2000, but these patches represented only a very small part of the total landscape. Proximity between host patches was also variable between sites and higher values of cohesion occurred during the first sampling season. The relationship between host area and D. kuscheli mean abundance was adjusted to an exponential (R2 = 77.5 %) model. Host patch dominance, host patch isolation, and host patch connectivity all showed a positive relationship with D. kuscheli mean abundance, adjusting significantly to linear models (R2 = 92%; R2 = 90%; R2 = 22% respectively). Outbreaks of Río Cuarto disease in the main maize production area of Argentina are related to high vector populations. The mechanisms by which D. kuscheli populations increased so much were not clear until now. The results presented here indicate that the abundance of D. kuscheli depends on factors related to the abundance and configuration of its host patches.

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