An experiment-based screening approach to formulate the entomopathogenic nematode Steinernema glaseri in pellets with powder materials

In this work, a discrete choice sequential approach for the pelletisation of the entomopathogenic nematode Steinernema glaseri is investigated. First, the pellets were made with agricultural soil (S), sugarcane bagasse ash (A), and diatomaceous earth (DE) in different proportions. Then, the physical stability and moisture retention ability were evaluated to select the best combinations for the pelletisation of infective juveniles (IJs) and the survival and pathogenicity on Galleria mellonella larvae were determined. Second, clay (C) and/or sodium polyacrylate (SP) were added to the best combinations to improve the moisture retention and, the survival and pathogenicity on Tenebrio molitor larvae were evaluated. The initial combinations selected were S85:A15:DE0, S50:A15:DE35 and S80:A15:DE5. The highest mean survival time (16.1 days) of IJs was obtained with S50:C15:DE35 and the pathogenicity in G. mellonella was 20 ± 6.40 %. The S15:C50:A15:DE20:SP1 mixture stood out for its lower moisture loss (90.17 %) when SP (1 g per 100 g of the mixture) and C were added, the survival of S. glaseri increases to 26.4 ± 0.433 days and increased the pathogenicity on T. molitor to 42.5 ± 7.9 %.