Spatial distribution of Cotesia flavipes (Cameron): Sampling performed using sugarcane stems

The objective of this study was to evaluate the spatial distribution of C. flavipes by using the methodology from the 1980s to assess whether the methodology is effective or requires modification. Two areas (100 × 100 m) of sugarcane were divided into 100 plots (10 × 10 m). In each plot, 10 stems of sugarcane with 1 D. saccharalis larva inside each stem were fixed in the soil and kept in the field for 2 days. Parasitism without the release of parasitoids (control) and with parasitoids released at 4 points spaced 50 m apart (1,500 parasitoids per point) was evaluated. We calculated aggregation indices; negative binomial distribution, Poisson distribution and geostatistical maps were constructed. To the control was not possible to calculate the indices of dispersion due to the absence of parasitized larvae. After the release of the parasitoid, the variance/mean ratio indicated a clustered distribution in the 2 areas. Morisita index values of 3.26 and 10.0 were observed for the replicate areas 1 and 2, respectively. Positive values were obtained for Cx and binomial distribution showed no significant difference to observed frequency that characterized aggregation. The parasitism mean was 0.25 parasite larvae at every 20-m radius, except for some spots that showed a parasitism mean of 2.97. The results showed that the studied areas were not affected by nature parasitism, and the release of 4 cups per hectare was not efficient for the effective control of the pest in the field.