Sequential sampling for estimation of overwintered sunn pest, Eurygaster integriceps Put., in wheat fields in Firozabad region of Ardabil province and identification of its natural enemies

Bakhshizadeh, Nakisa and Asghar Fathi, Seyed Ali and Mohiseni, Abdolamir and Nouri-Ganbalani, Gadir (2011) Sequential sampling for estimation of overwintered sunn pest, Eurygaster integriceps Put., in wheat fields in Firozabad region of Ardabil province and identification of its natural enemies. Other thesis, University of Mohaghegh Ardabili.

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Abstract

The sunn pest, Eurygaster integriceps Put., is an important pest of wheat and barely in Firozabad region of Ardabil province. The present study was conducted in rainfed wheat fields during 2009 and 2010, with using 1, 0.5 and 0.25 m2 quadrates. Comparison of defined three quadrate sizes for sampling of overwintered sunn pest showed that, using the smallest quadrate has prefer because of high precision and lower cost for sampling. Spatial distribution pattern of overwintered sunn pest investigated by using mathematical distributions, dispersion indices and regression techniques. According to mathematical distributions, spatial distribution of overwintered sunn pest fitted with the negative binomial (aggregated distribution) better than the poison (random) distribution. Also, dispersion indices include variance-mean ratio, index of patchiness, K index and Morisita index used for determination spatial pattern of overwintered sunn pest. Results of all indices showed aggregated distribution of this pest in Firozabad region. Further, based on R2 of regression analysis, both of Taylor power law and Iwao patchiness regressions showed aggregated pattern for overwintered sunn pest. The decision lines in Wald's sequential sampling plan were calculated for defined three quadrate sizes in three treatments including: using of deltamethrin (decis) made in Iran, deltamethrin (decis) made in Germany and fenitrothion made in Italy. Also, fixed precision sequential sampling plans (Green's and Kuno's models) were designed for estimating population density of the sunn pest at three fixed precision levels of 0.1, 0.15 and 0.25. Green's and kuno's fixed precision sequential sampling plans were validated using 10 - 15 independent data sets. In Green's model, the average sample number (ASN) in 0.25 precision level (which in generally accepted in IPM programs) for 1, 0.5 and 0.25 m2 quadrates were 21, 23 and 29 quadrates, respectively. Further in Kuno's model, the ASN in 0.25 precision for the three studied quadrates were 22, 25 and 31 quadrates, respectively. These results showed that sequential sampling programs could reduce required sample sizes between 46 to 88 percentage. Therefore, sequential sampling programs could be useful for population estimation of overwintered sunn pest and decision for management of the sunn pest in rainfed wheat fields.

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