Three dimensional temporal and spatial distribution of adult Oryzaephilus surinamensis and Sitophilus oryzae in stored wheat under different temperatures, moisture contents, and adult densities

Three dimensional temporal and spatial distributions of adult Oryzaephilus surinamensis at densities of 0.1, 1.0, and 5.0 adults/kg wheat (referred to as A/kg) and adult Sitophilus oryzae at densities of 1.0, 5.0, and 10.0 A/kg were determined in bins filled with 1.5 t wheat having 11.0 ± 0.8, 13.0 ± 0.6, or 15.0 ± 0.5% moisture content at 20 ± 1, 25 ± 1 or 30 ± 1 °C. At each of the five sampled locations, wheat was separated into three 15 kg vertical layers and the number of adults in each layer was counted.Less than 30% of adult O. surinamensis were recovered in the top layer, while more than 80% of adult S. oryzae were recovered in the top layer. Adults of O. surinamensis preferred the center locations in each layer and adults of S. oryzae preferred the top layer. Densities of both species at adjacent locations in the horizontal direction were autocorrelated with each other. The temporal continuous property might not exist for the adults of O. surinamensis but exists for the adults of S. oryzae. Even though both species had aggregated and clumped distribution at any temperature, moisture content and adult density, adults of O. surinamensis had a more homogeneous distribution than S. oryzae. These characterized patterns of distribution of adult insects could be used to effectively estimate their density inside stored grain-bins.

► The two adults had different preferences in their distribution in a 1.5 t wheat bin.
► More than 80% of Sitophilus oryzae were recovered in the top layer.
► Less than 30% of Oryzaephilus surinamensis were recovered in the top layer.
► Densities of S. oryzae in the horizontal direction were autocorrelated.
► The temporal continuous property might not exist for the adults of O. surinamensis.