Ecological aspects of an isolate ofSteinernema diaprepesi(Rhabditida: Steinernematidae) from Argentina

Abstract

Ecological aspects of Steinernema diaprepesi isolate SRC were studied to evaluate the species potential as biological control agent of insect pests. Under laboratory conditions, the following aspects were determined: the nematode life cycle, pathogenicity to several arthropods, reproductive capacity, tolerance to desiccation, effect of temperature on survival and infectivity of infective juveniles (IJs), and influence of soil texture and soil water potential on the isolate. The parasitic cycle on last-instar larvae of Galleria mellonella at 25°C was completed 8 days after infection. The nematode showed high virulence to lepidopteran larvae, being limited or nil in the remaining orders of arthropods evaluated. An acceptable offspring production of S. diaprepesi was confirmed in the species G. mellonella and S. frugiperda, suggesting that the isolate would have potential for control of lepidopteran larvae. Optimum temperature for reproduction was 20-25°C. IJs survived exposure to a range of temperatures between 10 and 40°C, with a significant reduction in the number of live IJs at 40°C. The nematodes remained infective at 20-40°C. IJ mortality was 100% on day 6 of exposure to 85% RH. The movement of IJs observed in the soil column experiments revealed that the isolate uses a cruiser-type search strategy. Soil texture and water potential significantly influenced IJ movement, search and penetration of G. mellonella larvae. The efficacy of this isolate was found to be favoured in sandy soils, regardless of the soil water potential.

Steinernema diaprepesi (Rhabditida: Steinernematidae) parasitizing Gonipterus platensis (Coleoptera: Curculionidae)

“…The high death of G. platensis pupae after inoculation of the three IJ concentrations confirms their susceptibility to S. diaprepesi and the potential of this nematode for managing this pest, as reported for G. mellonella and S. frugiperda [29]. The G. platensis mortality rate is related to the association of S. diaprepesi with the symbiotic bacterium X. doucetiae [27], which when released into host haemocele, promoted rapid degradation of the host pupae.…”

“…This nematode S. diaprepesi was first identified in Diaprepes abbreviates Linnaeus (Coleoptera: Curculionidae) larvae in Florida, USA [ 23 ] and, in South America, only in Venezuela and Argentina [ 27 ]. Steinernema diaprepesi is highly virulent for lepidopteran larvae such as those of Galleria mellonella L. (Lepidoptera: Pyralidae) and Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), due to its association with the symbiotic bacterium Xenorhabdus doucetiae Tailliez, Pagès, Ginibra & Boemare, 2006 [ 27 , 29 ]. Therefore, the detection of S. diaprepesi in eucalyptus crops in Brazil can contribute to programmes for integrated management in this culture in the country.…”

Biological control of Alphitobius diaperinus with Steinernema rarum CUL and Heterorhabditis bacteriophora SMC and feasibility of application in rice hull

“…Ten larvae or adults of the insect were put in each Petri dish; then, 500 IJs (Del Valle et al 2014) contained in 0.5 ml of aqueous solution were surface applied to the test arena (insects were not directly sprayed because once the insects were introduced in the dish, they immediately moved downwards). Control treatments consisted of the addition of an equal volume of distilled water on each substrate and tested insect stage.…”

Assessment of entomopathogenic nematodes and their symbiotic bacteria to control the stink bugs Euschistus heros and Dichelops melacanthus (Heteroptera: Pentatomidae) in the soybean-corn succession system

“…The similarity in mortalities caused to E. heros on the two layers thicknesses (1 an 5 cm) of each substrate may suggest an equal attraction of the IJs to the surface in an attempt to reach the adults moving there. S. diaprepesi is considered to display a cruiser behavior (Del Valle et al, 2014), which can generate better results against buried insects in relation to those on the substrate surface (Banu et al, 2017).…”

“…These two nematodes were selected because they caused 100% mortality of E. heros in the first test and because they have different foraging behaviors. While S. diaprepesi displays a "cruise" behavior (Del Valle et al, 2014), seeking its target insects, the nematode S. carpocapsae displays an "ambush" behavior (Koppenhöfer and Kaya, 1996), staying in lurk waiting for the host to approach.…”