Field infestation of the invasive fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize in Southern Ethiopia

Abstract

The biggest obstacle to Ethiopia's maize production is the fall armyworm (FAW), Spodoptera frugiperda. Since its recent introduction, the pest has assumed a key pest status displacing most other stalk borer insects known to attack maize in the country. This study was carried out to assess the infestation of FAW on maize, identify associated natural enemies, and determined the geographic distribution of the pest in southern Ethiopia. Infestation by FAW was encountered in most surveyed areas. The earwig, Doru luteipes (Scudder) was frequently found preying on larvae of FAW while the larvae of Chrysoperla rufilabris (Burmeister) were observed feeding on FAW egg masses. Megaselia scalaris (Loew) and Palexorista zonata (Curran), two parasitoids of FAW, were recovered from FAW larvae. The entomopathogenic fungus, Beauveria bassiana, was isolated from the cadaver of FAW larvae. Modeling the distribution of FAW revealed that there are many suitable places in southern Ethiopia, with low-lying plain lands having the greatest potential for pest invasion. With AUC values above 0.9, the MaxEnt models demonstrated great prediction accuracy. Precipitation in the driest month (27.3%) and precipitation in the coldest quarter (25.4%), accounted for more than half of the variance in the pest's potential distribution. The findings of this study have contributed to a greater understanding of field infestation of FAW and associated natural enemies. The species distribution model result constituted a crucial point in providing the rationale for devising management strategy by taking into account a specified area susceptible to enhance invasion risk by FAW.