Assessing the impact of site-specific spraying on control of Eurygaster integriceps (Hemiptera: Scutelleridae) damage and natural enemies

Abstract

Sunn pest, Eurygaster integriceps Puton is a key pest of wheat and barley in Iran. In this study, the impact of site-specific spraying on control of sunn pest damage and densities of the natural enemies was compared with the whole-field spraying method in 2009 and 2010. Three plots were assigned to each spraying method and two others were left untreated as control. The plots were divided into 11 × 11 m grids. Adults of E. integriceps were sampled using the distance-walk method. Coccinellids, Chrysoperla carnea and nymphs of sunn pest were sampled using a sweep net. Spatial analysis of datasets was done using Geostatistical Analyst extension of ArcGIS 9.3. The spatial analysis indicated that the adults and nymphs of E. integriceps had aggregated distribution in space and that site-specific spraying was applicable. Whole-field spraying was carried out when the mean density of E. integriceps in plots exceeded the economic threshold. In the site-specific spraying method, decamethrin ([cyano-[3-(phenoxy) phenyl] methyl] 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane-1-carboxylate) was applied to the grid cells with densities above the economic threshold. Site-specific application reduced the insecticide input by ca. 40–50%. The numbers of C. carnea and coccinellids were higher in site-specifically sprayed plots compared with whole-sprayed plots after treatment. The mean numbers of nymphs were not significantly different (P < 0.01) in whole-field and site-specifically sprayed plots. Percent damaged grain was below the economic damage threshold in all treated plots. It can be concluded that site-specific spraying has the potential to control E. integriceps at an acceptable level along with reducing the amount of insecticide used. It also conserved natural enemies in untreated refuges.