Estimating Economic Thresholds and Economic Injury Levels for Schizaphis graminum (Rond.) and Sitobion avenae Fab. Infesting Wheat Plants in Najaf Government, Iraq

Document Type : Original Article

Authors

1 Econ. Entomol. Dept., Fac. of Agric., Mansoura Univ., Egypt.

2 Dept. of Plant protection- College of Agriculture – University of Baghdad.

Abstract

Wheat (Triticum aestivum L.) is a vital cereal crop in Iraq and worldwide, but its productivity is threatened by cereal aphids, particularly Schizaphis graminum and Sitobion avenae. This study estimated the economic injury level (EIL) and  economic threshold (ET) for both species during two successive seasons (2023–2024 and 2024–2025) in Najaf Governorate, Iraq. Caged experiments involved artificial infestations at early, mid, and late growth stages, with varying aphid densities ranging from 0 to 50 individuals per tiller . Grain weight and yield loss were estimated to determine those economic limits. Results showed that aphid density and infestation timing significantly influenced crop yield, with mid-season infestations of S. graminum and late-season infestations of S. avenae caused the greatest losses. In 2023–2024, the lowest EIL were recorded in mid infestations for S. graminum (4.886 aphids/feddan) and S. avenae (2.887 aphids/feddan). In 2024–2025, S. graminum showed the lowest EIL in mid infestation (0.46 aphids/kg), while S. avenae reached the lowest in late infestation (0.28 aphids/kg). These findings highlighted the necessity for plant stage-specific integrated pest management, prioritizing aphid control during the most susceptible growth phases to minimize economic losses. These thresholds provide a basis for optimizing control decisions while reducing unnecessary pesticide use.

Keywords

Journal of Plant Protection and Pathology
Volume 16, Issue 9
September 2025
Pages 463-468

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