Occurrence and pathogenicity of entomopathogenic nematode isolates in maize growing regions of Ethiopia

Abstract

The objective of this study was to find and test entomopathogenic nematodes (EPNs) native to regions of Ethiopia where maize is grown with the aim of developing a biocontrol program against fall armyworm (FAW) Spodoptera frugiperda (Smith) and other arthropod pests. Six hundred seventy-nine soil samples were collected from eight regional states of Ethiopia between August and October 2019. From these collections, 28 EPN isolates, 13 from Steinernema genera and 15 from Heterorhabditis genera have been identified. All the 28 isolates identified from the survey and nine Ambo Agricultural Research Center’s isolates were tested using a single dose (500 infective juveniles ml^-1(IJ)/ml) under laboratory conditions using FAW larvae in completely randomized design. Isolates, such as Aso-Tes-287 from Steinernema genera and Am-Ger-Tes-74, Am-Adm-Tes-369, and Z9 from Heterorhabditis genera caused significant larval mortality within eight days. Moreover, the LT₅₀ values i.e., 3.5 to 6.7 days showed that these isolates are more virulent. These most virulent isolates were further tested for their potential in a pot experiment under wire house conditions at three different concentration levels (250, 400, and 600 IJ/ml) in randomized complete block design. The isolates Aso-Tes-287 and Am-Ger-Tes-74 resulted in higher mortality of 74.7% and 78.3%, respectively at 600 IJ/ml. The EPN isolates Aso-Tes-287 and Am-Ger-Tes-74 which caused higher mortalities within shorter periods, were promising bio-agents for the management of FAW. A confirmatory study is suggested to use the two promising bioagents for the management of FAW and other arthropod pests.