Survival and Infectivity of Entomopathogenic Nematodes Formulated in Sodium Alginate Beads

Abstract

An alternative control method to the use of chemical insecticides against soil dwelling insect pests is the application of entomopathogenic nematodes formulated in alginate beads for enhanced shelf life. The aim was to compare the benefit on nematode survival and infectivity of: (i) pre-conditioning of juveniles, and (ii) coating of alginate beads. The nematodes Steinernema glaseri, Steinernema carpocapsae, and Heterorhabditis bacteriophora were reproduced in last instar larvae of the wax moth Galleria mellonella and the infective juveniles emerged were subjected to two capture treatments: white traps and plaster of Paris, the latter was utilized as a pre-conditioning treatment. A total of 1,000 infective juveniles were formulated in each sodium alginate bead with or without an alginate coating. The beads were stored at 23 ± 3°C and a bidistilled water suspension of nematodes was set as a control. The survivorship of these formulates and their infectivity on Galleria mellonella larvae were evaluated every 7 d post-formulation (dpf). In beads without pre-conditioning juveniles nor coating, Steinernema carpocapsae had the higher survival rate (58.8%), the longest survival time (28 dpf) and the higher infectivity (100%) as well. Pre-conditioning improved the survival and infectivity of Steinernema glaseri by 22.5% at 21 dpf and 70.0% at 14 dpf, respectively. Alginate coating increased survival (21.7%) and infectivity (95%) of Heterorhabditis bacteriophora for up to 28 dpf. The combination of pre-conditioning and coating slightly favored the survival (10% for up to 14 dpf) of Steinernema glaseri and infectivity (100% for up to 35 dpf) of Steinernema carpocapsae. Non pre-conditioned Steinernema carpocapsae formulated in uncoated beads was the combination with better performance in survivorship (58.8%) and infectivity (100%) at 28 dpf. It was concluded that non pre-conditioned Steinernema carpocapsae formulated in uncoated beads was the combination with better survivorship and infectivity.

Formulation of Entomopathogenic Nematodes for the Control of Key Pests of Grapevine: A Review

“…Ehlers (2007) suggests that, for an EPN formulation to be a successful product, it should be formulated soon after nematode production so as to limit the formulation of dead nematodes, which might compromise the storage process. To improve the large-scale use of EPNs as biological control agents, ongoing research focuses on the development of IJ formulations that are cost-effective, that can survive storage at room temperature for relatively long periods, that can be transported and applied easily, and that have high infectivity against host insects (Shapiro-Ilan et al, 2012;Grzywacz et al, 2014;Ruiz-Vega et al, 2018).…”