Sequential sampling model with fixed precision level of the English grain aphid, Sitobion avenae in wheat fields of the Mahidasht region, Kermanshah

Spatial distribution of the English grain aphid, Sitobion avenae (F.), was studied in wheat fields of Mahidasht, Kermanshah province and Sequential sampling models with fixed precision level were prepared for its monitoring. Sampling was conducted during five years. At each sampling date, 100 tillers were randomly visited. The mean range of population density in wheat field was 0.39-34.01 aphids/ tiller. Taylor's Power Law parameters were used to preparing sampling models according to Green (1970). Spatial distribution was determined as cumulative. Sample size decreased with increasing aphid population density in sampling models. In research precision level of (0.1), the sample size required at the highest average population density observed in the field (34.01/ tiller) was 136, which in precision level proposed for integrated pest management (0.25) reduced to 22 tillers. Overall, due to the large sample size at the precision level of 0.1, the model prepared at the precision level of integrated pest management (0.25) was recommended for monitoring S. avenae. The recommended model can reduce sample size more than six times at different densities in comparison to the sequential sampling model at the precision level of 0.1.