Effect of moisture evaporation from diatomaceous earth pellets on storage stability of Steinernema glaseri

ABSTRACT

Induction of anhydrobiosis and storage stability of entomopathogenic nematodes are influenced by moisture availability. Decreasing moisture content in diatomaceous earth (DE) pellets containing the Steinernema glaseri NJ-43 strain and its effect on survival time and infectivity of the nematode were determined. Pelletisation was performed in a vortex mixer, using DE Celite® 209 as the desiccant material. Pellets were stored at room temperature (23 ± 2°C) and high relative humidity (96–100%). Nematode survival and infectivity against last instar greater wax moth, Galleria mellonella, were tested daily. Initial average and average equilibrium moisture content in pellets were 66.7% and 13.6%, respectively, and the infective juveniles mean survival time was 8.8 days. A moisture transfer model based on diffusion and evaporation was evaluated to predict moisture fluctuations within the pellets. We concluded that 84% of variation in S. glaseri infectivity on G. mellonella larvae was explained by the survival of the nematode, whereas 52% of variation in S. glaseri survival was explained by the loss of moisture from the pellets. The moisture transfer model achieved 78% reliability in predicting moisture content and fluctuations. Therefore, the mechanisms of moisture diffusion and evaporation from the surface to the surrounding atmosphere contribute significantly to moisture loss from the pellets.

KEYWORDS:

• Entomopathogenic nematode
• desiccation
• pelletisation
• diffusion
• evaporation
• modelling

Acknowledgements

The authors would like to thank Professor Carlos Martínez Alvarez for his help over the course of this research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to thank to the Instituto Politécnico Nacional (IPN) of México, to the Commission to Operation and Foment of Academic Activities (COFAA-IPN) and to the SIP project 20140535 for funding this work, to the CONACYT for the scholarship 336753 granted to Carlos I. Cortés-Martinez.