Distribution and sampling of Sitophilus zeamais (M.) in wheat grains stored in a metallic bin

摘要

> face="Verdana" size="2"> The objective of this work was to determine the type of distribution of Sitophilus zeamais (Mostch., 1895) in a grain mass and to estimate the number of samples required for design of monitoring program for the insect-pest. A metallic bin filled with 12,5 t of wheat (type durum; harvested in Sept. 1998) was utilized. The wheat was infested with S. zeamais during the bin loading to obtain 1 insect kg-1 of grains. Grain sampling at three depths was carried out every eight days for three months. After weighing, the grain samples were sieved to isolate and allow insect counting. In order to characterize the type of the distribution of the Sitophilus population, three techniques were used: Iwao?s patchness, Taylor?s power law and Morisita?s index. Despite Iwao?s and Taylor?s techniques providing the same distribution characterization, Iwao?s technique was preferred because it is less affected by sample size, location and sampling intervals. The determination of the number of samples was based on the mean number of insects collected per sample. The results obtained indicated that a smaller number of sample is required for the detection of high insect densities.