University of California, Riverside

Department of Nematology

Irma De Ley

Irma De Ley Irma Tandingan De Ley

Associate Research Specialist
Department of Nematology/Entomology
2126 Genomics
Office phone: (951) 827-3914
Fax: (951) 827-3719



My research objective in the last five years centered on biological control. From a wider search for biological control agents against invasive gastropods in California nurseries, now I focus on the biological control potential of Phasmarhabditis hermaphrodita, a nematode that has been commercialized (Nemaslug ®) and used effectively for over 20 years in 14 European countries. My research is made possible through two consecutive grants from the California Department of Food and Agriculture (CDFA) Specialty Crops, with collaborators Rory McDonnell (Oregon State University, Corvallis, OR); Timothy Paine (Project Director) in the Department of Entomology, UCR; and Paul De Ley, Department of Nematology, UCR.


Research Highlights

a). We first reported the presence of invasive slug Boettgerilla pallens Simroth in the US (McDonnell, et al., 2014); first recorded P. hermaphrodita and P. papillosa in North America (Tandingan De Ley et al., 2014; Tandingan De Ley et al., 2016) from invasive slugs; described and first reported the new species of Phasmarhabditis californica (Tandingan De Ley et al, 2016); and Alloionema similis (Holovachov et al., 2016) from California nurseries; identified gastropod-associated nematodes that belong to at least 12 major families, including among others: Rhabditidae (Oscheius dolichura Schneider and O. tipulae Lam & Webster; Caenorhabditis elegans Maupas), Diplogasteridae (Protodiplogasteroides or Pseudodiplogasteroides), Cosmocercoidea (Cosmocercoides sp.), and Alloionematidae (Alloionema spp).

 Following discovery of three Phasmarhabditis spp we evaluated their lethal effects on invasive slugs, snails and non-targets.

b). We demonstrated that P. hermaphrodita US isolate caused significant to highly significant mortality on Lehmannia valentiana (Valencia slug, LV), Deroceras reticulatum (grey field slug, DR), Cornu aspersum (European brown garden snail) and Lissachatina fulica (giant African land snail, GALS)neonates at rates equivalent to or higher than Nemaslug®’s recommendation of 30 IJs/sq cm. It also infects LV, GALS and Limacus flavus (Tawny garden slug) all of which are new host records. A lethal effect of P. hermaphrodita on GALS is important, considering this invasive’s economic, environment and health risks.

c). We demonstrated that P. hermaphrodita US isolate does not cause mortality and is safe to four earthworm species Amynthas gracilis (Alabama jumper), Eisenia fetida (Red wigglers), Eisenia hortensis (European night crawler) and Lumbricus terrestris and therefore may be used as a safe molluscicide in nurseries, backyard gardens, or field crops.

 d). We demonstrated that the three Phasmarhabditis spp is safe to non-target decollate snails (Rumina decollate) that are currently in the market for biological control of C. aspersum in 12 counties of California.


Other Research Interests

Using a combination of morphology/morphometry and molecular sequencing/ barcoding for species diagnostics; ecology; taxonomy; systematics and phylogeny; I also collaborated and/or spearheaded research on e.g. bioinventory of nematodes in Philippine rice ecosystems (Pascual et al., 2014) and at a Philippine biodiversity hotspot and UNESCO world heritage site (Qing et al., 2015; Quisado et al., 2015); and on research that evaluated the impact of soil amendment on root knot and free-living nematodes (Ritzinger et al., 2014).


Prior affiliation; teaching and research experience:

under construction)

Videos and images of slug nematodes and gastropods:

The use of the CA isolates of Phasmarhabditis as a mollusk-killing biopesticide (reference #3868.040WO1):
Key to identification of California slugs:
Snail and Slug research on Facebook:
Identification, management and other information on California pest snails and slugs, UC Division of Agriculture and natural Resources:


Gastropods from the zoo:

 Glass snail (Oxychilus sp) Deroceras reticulatum (Gray field slug)
Glass snail (Oxychilus sp) and Deroceras reticulatum (Gray field slug)
Ariolaimax californicus (Banana slug)
Ariolaimax californicus
(Banana slug)


Phasmarhabditis-infected gastropods::

Lehmannia valenciana (Valencia slug)Lehmannia valenciana (Valencia slug)
Lehmannia valenciana
(Valencia slug) infected with Phasmarhabdtis hermaphrodita


Phasmarhabditis images and videos coming soon!


Other Links:

Research Gate, to download pdf of publications:
Google scholar pubs/ citations
Image Maps/Videos of terrestrial nematodes:
Hirschmanniella santarosae:
Hirschmanniella pomponiensis
Hirschmanniella belli:
Hemiplectus muscorum:
Links to other video-capture specimens

More Information

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Department Information

Department of Nematology
Margarita Flores
1447 Boyce Hall

Tel: (951) 827-3598
Fax: (951) 827-2364