Soil texture, infective juvenile concentration, and soil organic matter influence the efficacy of Steinernema feltiae isolate Lican Ray.

Gabriela Lankin,Carlos Castaneda-Alvarez,Ernesto San-Blas,Geraldine Allende,Giselle Vidal-Retes,Erwin Aballay

doi:10.21307/jofnem-2020-007

Gabriela Lankin, Carlos Castaneda-Alvarez + Show 4 more

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https://doi.org/10.21307/jofnem-2020-007

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Abstract

The influence of infective juveniles (IJs) concentration, soil texture, IJ-host distance and organic matter (OM) content, at different decomposition degree, on the activity of the nematode Steinernema feltiae isolate Lican Ray (LR) was examined using Galleria mellonella larvae. Bioassays were conducted in tubes of varied length, filled with soil of different textures, placed either vertically or horizontally. In the concentration assay, highest IJ concentrations caused maximum larval mortality in all soil types (440, 2,200 and 4,400 IJs in clay, loam and sandy loam). In the second assay, soil texture (loam, clay or sandy loam) interacted significantly with IJ-host distance (10, 20, 30, 40 cm, horizontally; 30, 50, 70 cm, vertically), and distances of 30 cm or more affected IJ effectiveness on the control of G. mellonella. The effect was stronger in clay and sandy loam than in loam soils, where IJ moved up to 40 cm horizontally and 70 cm vertically. In the third assay, OM content (0, 2, 4, 6 and 8%) and its decomposition degree (initial, medium and advanced) did not interact to influence IJ movement in all treatments that contained any percentage of OM (2–8%). Only in the soil with no OM, IJ did not cause death of larvae at all. These results show the potential of S. feltiae LR to be used in different soil textures, as long as the content of soil OM allows its dispersal and host infection, in order to optimize the pest-control activity of the nematode.

Highlights

Steinernema feltiae (Nematoda: Rhabditidae) is a soil dwelling entomopathogenic nematode (EPN) that can exploit a wide range of insect hosts
At three days after inoculation (DAI) the analysis showed no interaction between infective juveniles (IJs) concentration and soil types (F(4,36) = 1.13; p = 0.357) factors were analyzed inde pendently
Considering the factor soil texture, and independently from the IJ concentration, the highest G. mellonella mortality occurred in loam soil (96%), followed by clay soil (75%), and sandy soil (50.7%), and significant differences were observed only between loam and sandy soils (F(2,36) = 9.59; p ≤ 0.0001; Fig. 2I, capital letters)

Summary

Introduction

Steinernema feltiae (Nematoda: Rhabditidae) is a soil dwelling entomopathogenic nematode (EPN) that can exploit a wide range of insect hosts. The potential of nematode of this genus for the control of several pest species has been demonstrated in Lepidoptera (Radhakrishnan et al, 2017), Coleoptera (Gulcu et al, 2019), Diptera (Chergui et al, 2019), among others Biotic factors such as antagonist organisms, abiotic factors, such as soil texture, moisture, temperature and content of organic matter (OM), and others, such as IJ concentration, application method and distance from the host, affect the effectivity of the IJ (Choo and Kaya, 1991; Shapiro et al, 2000; Sharma et al, 2011; Griffin, 2015). H. bacteriophora, S. carpocapsae and Steinernema glaseri dispersed significantly more in sandy loam than in loam or silty clay loam (PortilloAguilar et al, 1999) This may vary with EPNs species and isolate, as in a study by CamposHerrera and Gutiérrez (2014), where infection dynamics varied among 14 different populations of S. feltiae in the same soil texture. Texture, OM and IJ concentration are factors to consider for optimizing EPN activity, and they should be evaluated for different species

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