Development of bio-pesticide for management of spodoptera frugiperda (j. e. smith) and other lepidoptera pests of maize in Tanzania

Abstract

This study was conducted to evaluate the infestation levels and develop management option for a Lepidoptera namely fall armyworm (Spodoptera frugiperda J. E. Smith). The survey was carried out in three regions of northern Tanzania namely; Kilimanjaro, Arusha and Manyara regions, and bioassay tests were conducted at the Hunan University of Technology and Nelson Mandela African Institution of Science and Technology. Six villages per region were surveyed, and a total of 210 maize growers were interviewed in all regions during maize growing season in 2018. A scale of 0 (no damage) to 9 (100 % damage) was used to assess severity of S. frugiperda in the study area. Performance of bio-based formulation against G. mellonella and S. frugiperda were measure by the percentage of insect mortality recorded 2 days and 9 days post-treatment for entomopathogenic nematodes and plant extracts treatments respectively. Data collected were analyzed using GenStat software 16 th edition and SPSS version 21. Results indicated that S. frugiperda incidence and severity level on maize were 66.59 % and 5.422; 52.96 % and 4.756; 52.64 % and 3.989 for Arusha, Kilimanjaro and Manyara regions respectively. The commonly applied pest management options by farmers in the study area were synthetic pesticides (86 %) and non-synthetic methods (14 %). Laboratory experiment showed that, formulations from Tephrosia vogelii and Dolichous kilimandscharius caused S. frugiperda larvae mortality of up to 70 % and 60 % respectively. Bio-based formulations from entomopathogenic nematodes (40 IJ/ml) caused G. mellonella larvae mortality of up to 100 %. On the S. frugiperda, the same nematodes concentration caused high mortality 48 h after treatment indicating that it can be used against S. frugiperda. Bio-formulation of nematodes in UV protecting ingredients caused higher larvae mortality (20 %) than the aqueous formulation (0 %) under direct sunlight for 6 h, indicating that nanoparticles protected the nematodes against UV radiation. Of the two biopesticide formulations, entomopathogenic nematodes had high performance, and thus, this study recommends the use of entomopathogenic nematodes for the management of S. frugiperda and other Lepidoptera. However, further study on their performance in different agricultural systems is needed.