A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor
of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and
Technology
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
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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.