Geographic distribution, relative importance, and association of factors influencing fall armyworm [Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)] on maize (Zea mays L.) in Southern Ethiopia

Abstract

Spodoptera frugiperda is considered the most severe maize pest in the world and Ethiopia as well. A survey was conducted during the 2017 and 2018 cropping seasons to determine the distribution, relative importance, and the association between S. frugiperda intensity and biophysical factors. A total of 375 maize fields were surveyed during the two cropping seasons. The spatiotemporal analysis revealed that there was a 100% prevalence of the S. frugiperda with various degrees in both cropping seasons. However, significant variations were observed in the pest incidence and plant damage severity of S. frugiperda among the surveyed districts in the two seasons. There were higher pest incidence and plant damage severity in 2017 than in the 2018 cropping season. Logistic regression analysis was used to analyze the association of S. frugiperda with biophysical factors. Higher (> 75% for both cropping seasons) S. frugiperda plant damage severity was highly associated with Denba Gofa, Zala, Arba Minch, cropping system, altitude, pest management, insecticide spray frequency, and weeding practice with variable levels of significance. Lower plant damage severity of S. frugiperda was highly associated with Burji, high intercropping, altitude, a cultural plus insecticide used in pest management, more than two times insecticide applications, and high weeding practice. The study suggests proper pest management practices should be carried out to reduce S. frugiperda damaged to the maize crop.

Keywords:

• Biophysical factors
• maize
• regression analysis
• severity
• S. frugiperda
• spatiotemporal analysis

Acknowledgments

The authors gratefully acknowledge the Southern Agricultural Research Institute and Arba Minch Plant Protection Clinic for providing the necessary research fund and technical support for conducting the survey research, respectively. Special appreciation goes to our colleagues who supported the researchers with indisputable and unreserved support during the survey period, especially Tariku Simion, Selamawit Markos, Tsebaye Tsala, and Betsegaw Yato, Mulalem Mersha, Yemane Woldeyohanis, and Biya Tadesse. Last but not least heartfelt thanks go to Bereket Gebresilassie (MSc) for his willingness to sketching the map of the surveyed areas.