Intraspecific virulence of entomopathogenic nematodes against the pests Frankliniella occidentalis (Thysanoptera: Thripidae) and Tuta absoluta (Lepidoptera: Gelechiidae)

Raquel Campos-Herrera; Ignacio Vicente-Díez; Magda Galeano; Maryam Chelkha; María Del Mar González-Trujillo; Miguel Puelles; David Labarga; Alicia Pou; Javier Calvo; José Eduardo Belda

doi:10.21307/jofnem-2021-102

Intraspecific virulence of entomopathogenic nematodes against the pests Frankliniella occidentalis (Thysanoptera: Thripidae) and Tuta absoluta (Lepidoptera: Gelechiidae)

J Nematol. 2021 Dec 14:53:e2021-102. doi: 10.21307/jofnem-2021-102. eCollection 2021.

Affiliations

¹ Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de La Rioja, Gobierno de La Rioja) Finca La Grajera Ctra. Burgos Km. 6 Salida 13 Lo-20, Logroño 26007, Spain.
² R&D Department of Koppert España, S.L. Paraje Piedra Rodada, 470, Vícar, Almería 04738, Spain.
³ Research Team "Lombricidae, Improving Soil Productivity and Environment" (LAPSE), Ecole Normale Supérieure (E.N.S.), Centre Eau, Ressources Naturelles, Environnement et Développement Durable (CERNE2D), Mohammed V University, Avenue Mohamed Bel Hassan El Ouazzani, BP: 5118, Takaddoum - Rabat, Morocco.

Abstract

Entomopathogenic nematodes (EPN) are excellent biocontrol agents against various insect pests. Novel biotechnological approaches can enhance their utility against insects above-ground, opening a new venue for selecting superior EPN against certain insects. We hypothesize that different populations of the same species but from different origins (habitat, ecoregion) will differ in their virulence. This study aimed to evaluate the virulence of various EPN populations against two pests of worldwide incidence and damage to high value crops: Frankliniella occidentalis (Thysanoptera: Thripidae) and Tuta absoluta (Lepidoptera: Gelechiidae). We tested 10 EPN populations belonging to three EPN species: Heterorhabditis bacteriophora (Koppert, MG-618b, AM-203, RM-102), Steinernema feltiae (Koppert, RS-5, AM-25, RM-107), and Steinernema carpocapsae (Koppert, MG-596a). Each EPN population was tested at two concentrations. Frankliniella occidentalis was tested at 160 and 80 IJs/cm² and T. absoluta at 21 and 4 IJs/cm². Control treatments followed the same experimental procedure but only adding distilled water. Overall, whenever different, higher IJs concentration resulted in lower adult emergence, higher larval mortality, and shorter time to kill the insects. Considering the low concentration, S. feltiae provided the best results for both insects and instars investigated, while H. bacteriophora and S. carpocapsae required a high concentration to reach similar or slightly better results. Differences among populations of each of the species were detected, but only the native populations of H. bacteriophora populations showed consistently higher control values against both insects/instar compared with the commercial one. Differences among S. feltiae and S. carpocapsae populations depended on the IJs concentration, insect, and instar. We consider S. feltiae a very promising species for their application against F. occidentalis and T. absoluta, with the Koppert population as the most consistent among the populations tested. Specific EPN-populations of S. carpocapsae and H. bacteriophora were good candidates against certain instar/insects at high concentrations. This study emphasized the importance of intraspecific variability for EPN virulence.

Keywords: Aerial insect-pests; Heterorhabditis; Steinernema; Tomato.