Fixed Precision Sequential Sampling Plans to Estimate Overwintered Sunn Pest) Eurygaster integriceps Put.) Population in Rainfed Wheat Fields in Borujerd
Sunn Pest، Eurygaster integriceps Put.، is the most important pest of wheat and barley in most producing regions of Iran، including Lorestan province. Spatial distribution and fixed precision sequential sampling plans of Sunn pest by the use of two quadrate sizes 0. 25 and 0. 5 m2 were investigated in rainfed wheat fields in Borujerd during 2004 and 2005. Based on R square of regression، Taylor''s power law and Iwao''s patchiness regression models provided a more adequate description of variance-mean relationships for 0. 25 and 0. 5 m2 quadrate sizes، respectively. Taylor''s and Iwao''s were significantly >1، for two quadrate sizes، indicating that over-wintered Sunn pest population was aggregated in rainfed wheat fields. Fixed-precision sequential sampling plans (Green''s and Kuno''s model) were designed for estimating over-wintered adult stage of E. integriceps density at three fixed precision levels (0. 1، 0. 15 and 0. 25). For each quadrate size، Green''s and Kuno''s fixed precision sequential sampling plans were validated using 12 independent data sets ranging in density from 0. 09 to 2. 65 (for smaller quadrate) and 0. 1 to 5. 24 (for larger quadrate) over-wintered adults per quadrate. To achieve a precision of 0. 25 in Green''s fixed-precision sequential sampling (by use of 0. 25 m2 quadrate)، which is generally accepted in IPM programs، it is necessary to take samples with an average sample number (ASN) of 26. As the precision level was increased to 0. 10، average sample size (for smaller quadrate) increased to 157. For Kuno’s Fixed-precision sequential sampling plan (use of quadrate 0. 5 m2)، an average sample number of only 16 quadrates was necessary to achieve a precision level of 0. 25. As the precision level was increased to 0. 10، average sample size (for larger quadrate) increased to 90. Therefore، Green’s fixed precision sequential sampling plan (by use of quadrate 0. 25 m2) that has the least cost and the highest ASN was the most preferred and suitable quadrate size to forecasting of over-wintered adults of E. integriceps in rainfed wheat fields.