Mechanical production of pellets for the application of entomopathogenic nematodes: factors that determine survival time of Steinernema glaseri

Applications of infective juveniles (IJ) of entomopathogenic nematodes (EPN) formulated in pellets are still limited. This is principally due to limited advances in the technology of formulation. We aimed to develop a new method of mechanical formulation through material flow and to analyse its effect on the survival time of encapsulated EPN by varying the granular materials, the components of the aqueous suspension, the age of the nematodes and by applying a surface coating (C) to the pellet. Three-day-old and two-month-old Steinernema glaseri IJ were encapsulated with different proportions of diatomaceous earth (DE) and attapulgite clay (AC). The aqueous suspension containing the nematodes was prepared with double distilled water (DDW), varying proportions of Opuntia ficus-indica mucilage (OM) or gelatin (GL), and a sunflower oil surface treatment. The pellets were stored at an average room temperature of 23 ± 6°C. The best results were obtained with the following proportions: 100DE:0AC and 50DE:50AC, using the OM suspension, three-day-old nematodes and a surface C, which resulted in an average of 14 days survival time. These results confirmed that the nematodes do not die during mechanical encapsulation and that the age of the IJ as well as the loss of moisture during storage at room temperature were the factors that decreased the survival of encapsulated EPN. It was concluded that it is necessary to use neonate IJ and to reduce the moisture transfer rate in the granular structure in order to delay the desiccation of the encapsulated nematodes.