Screening of selected entomopathogenic fungi for virulence against larvae of the fall armyworm spodoptera frugiperda (J.E. SMITH)

Abstract

The Fall Armyworm, Spodoptera frugiperda originated from the tropical regions of the Americas and was first discovered in Africa in 2016, the same year it was reported in Uganda. It is a phytophagous pest that feeds on over 80 species of crops including maize which is an important food crop in Uganda. Current control is through the use of insecticides. However these pesticides pose threat to the environment and human health, but also the notorious pest has developed resistance towards them. Therefore there is need for integrated pest management for example through alternative use of bio-pesticides. This research assessed the microbial potential of Beauveria bassiana against the larvae of the fall army worm, and compared its efficacy against a known market pesticide Amdocs 3 EC. Experiments were carried out in the Entomology and pathology laboratory at the National Crop Resources Research Institute (NaCRRI) at Namulonge, Uganda. Different concentrations of the spores were used for the bioassay assessment. Laboratory assays demonstrated the capacity of the pathogen to infect the larvae at a temperature of 24 ±20C with substantial reductions in fall army worm larvae populations in all the spore concentrations used for treatment. The highest mortality was registered with the highest spore deposits. Similar mortality at the highest spore concentration was obtained with Amdocs 3 EC. The larvae treated with highest spore concentrations were observed to be emaciated. Synthetic insecticide Amdocs 3 EC caused mortality after very short period unlike the fungal extracts where the mortality was achieved over longer periods. Bring here one discussion statement, conclusion and way forward. The observed mortality is attributed to the ability of B. bassiana pathogens to infect the fall army worm under ambient-humidity conditions and the moderate temperatures that prevailed during the trials. However, it cannot be assumed that the success in these trials will translate to equal success in other regions with more severe climates. Therefore, larger and wider trials that take into consideration these variations should be explored.