Efficacy of alginate-based formulation of Steinernema carpocapsae IRMoghan1 against Mythimna loreyi (Lepidoptera: Noctuidae)

Abstract

ABSTRACT Entomopathogenic nematodes (EPNs) are effective biocontrol agents. Extending the shelf-life and storage at room temperature, along with maintaining their pathogenicity, are the most important goals of EPNs formulation. Alginate is a natural anionic polysaccharide utilised in manufacturing plant protection products. In the present study, two types of alginate-based capsules (containing 0.5% sodium alginate and 2% CaCl2·2H2O (w/v), and containing 2% sodium alginate and 0.5% CaCl2·2H2O w/v) were used for the formulation of infective juveniles (IJs) of Steinernema carpocapsae IRMoghan1. Additionally, the efficacy of the manufactured capsules against Mythimna loreyi Duponchel was evaluated. Based on the results, the survival rate of the nematodes was not significantly different among the treatments (including the two capsule types and water-suspended IJs) at 60 days after capsule formation; however, water-suspended IJs showed a significantly lower survival rate than the IJs extracted from both capsule types. The IJs extracted from the capsules containing 0.5% sodium alginate (w/v) and 2% CaCl2·2H2O (w/v) exhibited the highest and the water-suspended IJs showed the lowest pathogenicity against larvae of Galleria mellonella. Application of the alginate-based capsules manufactured with 0.5% sodium alginate (w/v) and 2% CaCl2·2H2O (w/v) against M. loreyi prepupae in the soil (at a dose of 800 IJs per insect) caused 75% insect mortality. Appropriate survival rate (74% for 120 days post-formulation at 24°C) and maintenance of pathogenicity of the nematodes over 120 days-period and effective application of the alginate-based capsules against M. loreyi is a promising successful prospect for the use of this formulation against soil pests.