New Control Strategies

This work is funded by an Oregon Department of Agriculture Specialty Crop Block Grant under Agreement Number ODA-18-010-GR
Project Title: Development of new biological control strategies for pest slugs

Project Scientists:

Dr. Rory Mc Donnell, Dept of Crop and Soil Science, Oregon State University, Corvallis OR 97331

Dr. Dee Denver, Dept of Integrative Biology, Oregon State University, Corvallis OR 97331

Dr. Man Yeon Choi, USDA-ARS, Horticultural Crops Research Unit, Corvallis OR 97331

Dr. Ruth Martin, USDA-ARS, Forage Seed and Cereal Research Unit, Corvallis OR 97331


Project Summary:

The most common control methods for slugs rely on chemical pesticides, which have low efficacy, many environmental risks and potential for chemical resistance. Therefore, growers are challenged with developing sustainable management strategies focusing on biological-based environmentally friendly alternatives. Currently in Europe a commercially available biocontrol product (Nemaslug®) comprising a nematode and its associated bacteria is being used to manage slugs. In fact, the efficacy of using this product can significantly reduce slug populations in crops. The recent discovery of this nematode in Oregon by Mc Donnell and Denver opens the door to serious consideration of the nematode as a potential biological control agent in the United States. Further method development by our team expands the potential of this nematode system to deliver specific bacteria as vehicles for additional biocontrol strategies. Choi and Martin recently published the slug transcriptome and hypothesize that genes expressing antimicrobial peptides in the epidermal mucus are a critical component of the immune system essential for slug survival. Therefore, we are looking at these genes as potential biological targets (i.e. RNAi) that, when knocked out, will critically impact slug survival. In this project, our objectives focus on examining nematodes and associated bacteria for their efficacy in slug control, and as a potential RNAi delivery system to develop new biocontrol strategies for pest slugs in specialty crops. Our team comprises a slug and snail expert (Mc Donnell), a nematode expert (Denver), RNAi specialist (Choi), and a molecular biologist (Martin).


Slug-killing nematode Phasmarhabditis hermaphrodita collected in Oregon


Project Goal and Objectives:

The ultimate goal of this project is to identify a highly virulent Phasmarhabditis-bacteria combination for potential use as a biological control agent of gastropod pests of specialty crops.

To achieve this goal the objectives of our research are to:

  1. Construct a vector and establish a nematode associated bacteria strain to express dsRNA, as a potential RNAi delivery system for slugs.
  2. Assess the virulence of different Phasmarhabditis-bacteria combinations against both pest and native (non-pest) slug species in laboratory infection trials.
  3. Confirm the virulence of the most lethal Phasmarhabditis-bacteria combination in microcosm studies (i.e. pseudo-field conditions) against the key gastropod pest, the gray field slug (D. reticulatum).
  4. Analyze the transcriptome and peptidome of infested slug epidermal tissue.
  5. Identify genes involved in the immune response to screen as potential RNAi targets.

Slugs are not only significant pests of specialty crops in Oregon, they are major pests of specialty crops throughout the US, and consequently our proposed research could provide an effective solution to pest gastropod management for growers of these crops throughout the nation.


Project Updates:

January 2019: We have successfully set up our pest slug colonies!

May 2019: We have constructed a L4440 plasmid vector for expressing dsRNA and for expressing the green fluorescent protein, and transformed it into the E. coli strain HT115 (De3) which lacks the dsRNA-degrading enzyme.

September 2019: We have co-transformed the fluorescence-emitting plasmids into E. coli HT115 (De3) strain, in order to make a visual tracking tool for the bacteria. We have also successfully isolated the fluorescence-emitting bacteria, which will be tested in nematodes.


Slug-killing nematode with fluorescing bacteria


Contact Us:

To contact the project team send an email to Dr. Rory Mc Donnell at
For additional information on slug pests damaging specialty crops, how to identify different species, and information on control strategies see the other tabs on this website.