Biological Control of Pest Non-Marine Molluscs: A Pacific Perspective on Risks to Non-Target Organisms

Abstract

Classic biological control of pest non-marine mollusks has a long history of disastrous outcomes, and despite claims to the contrary, few advances have been made to ensure that contemporary biocontrol efforts targeting mollusks are safe and effective. For more than half a century, malacologists have warned of the dangers in applying practices developed in the field of insect biological control, where biocontrol agents are often highly host-specific, to the use of generalist predators and parasites against non-marine mollusk pests. Unfortunately, many of the lessons that should have been learned from these failed biocontrol programs have not been rigorously applied to contemporary efforts. Here, we briefly review the failures of past non-marine mollusk biocontrol efforts in the Pacific islands and their adverse environmental impacts that continue to reverberate across ecosystems. We highlight the fact that none of these past programs has ever been demonstrated to be effective against targeted species, and at least two (the snails Euglandina spp. and the flatworm Platydemus manokwari) are implicated in the extinction of hundreds of snail species endemic to Pacific islands. We also highlight other recent efforts, including the proposed use of sarcophagid flies and nematodes in the genus Phasmarhabditis, that clearly illustrate the false claims that past bad practices are not being repeated. We are not making the claim that biocontrol programs can never be safe and effective. Instead, we hope that in highlighting the need for robust controls, clear and measurable definitions of success, and a broader understanding of ecosystem level interactions within a rigorous scientific framework are all necessary before claims of success can be made by biocontrol advocates. Without such amendments to contemporary biocontrol programs, it will be impossible to avoid repeating the failures of non-marine mollusk biocontrol programs to date.

Surface crawling and pedal surface collecting in aquatic gastropods: A case of scientific amnesia

“…As a consequence, attempts to tackle invasive Ampullariidae specifically by delivering molluscicides via the water surface predictably will affect native gastropod faunas. In the history of our efforts to control pest molluscs, lacking familiarity with the biology of non-target species has contributed to misjudgments with devastating consequences (chriStenSen et al 2021). This short review hopefully will help to avoid adding another failure to the list.…”

Thirty years of slug control using the parasitic nematode Phasmarhabditis hermaphrodita and beyond

“…Concern has been raised about the use of Phasmarhabditits species on nontarget organisms, 175 particularly native snail populations, yet there has not been one observation of these nematodes significantly affecting the health or populations of nontarget slugs or snails in 30 years of use across northern Europe. Also, there has been unease about the potential spread of M. osloensis (an opportunistic human pathogen) used to grow P. hermaphrodita , yet the bacterium these nematodes are reared on is not M. osloensis but a species closely related to P. faecalis , 135 which poses no threat to humans, so the level of risk to nontarget organisms associated with the use of the these nematodes remains low.…”

An Insight into Different Strategies for Control and Prophylaxis of Fasciolosis: A Review

“…Different compounds used as molluscicides for the control of trematode infection and their possible risks are given in Table 1. Other beneficial approaches to control fasciolosis include snails' biological control and fencing of the waterlogged region to prevent infected snails from direct contact with final hosts [19] . Other than chemical compounds, a variety of medicinal plants have been used as molluscicides around the world (Table 2).…”