What is a molluscicide?

A pesticide is an all encompassing term for a chemical or substance that kills unwanted animals, insects, plants or other organisms. It’s usually used in relation to large-scale agriculture, but sometimes used for domestic or commercial purposes. While herbicides and insecticides often dominate the conversation around pesticides, there are actually many other targeted pesticide types, such as nematicides, rodenticides, avicides and molluscicides.

Each of these terms refers to a pesticide targeted to specific animal or group of animals. Molluscicides are designed to kill mollusks, specifically snails and slugs in agricultural circumstances. Although this may be a slightly overlooked type of pesticide, it’s critical to many large- and small-scale gardeners and farmers. Learn more about how molluscicides work, what they target and which chemicals are most effective.

Understand molluscicides 
Molluscicides are pesticides which kill mollusks, an animal phylum of tens of thousands of invertebrate creatures. Mollusks include octopi and squid, as well as snails and slugs, which are usually targeted by molluscicides.

Slugs and snails are well-known by farmers and gardeners as some of the most annoying and destructive pests. They can destroy the leaves and fruit of a large variety of plants, old and young, according to the University of California Integrated Pest Management Program.

“Snails and slugs feed on a variety of living plants and on decaying plant matter,” UC IPM explained. “They chew irregular holes with smooth edges in leaves and flowers and can clip succulent plant parts. They also can chew fruit and young plant bark. Because they prefer succulent foliage or flowers, they primarily are pests of seedlings and herbaceous plants, but they also are serious pests of ripening fruits that are close to the ground such as strawberries, artichokes, and tomatoes. They also will feed on foliage and fruit of some trees; citrus are especially susceptible to damage.”

Luckily, these pests are easily noticeable by the silvery trails of dried mucus left behind by their foot. When farmers and gardeners spot the telltale signs and damage left behind by snails and slugs, it’s time to look to molluscicides for help.

As the U.S. Army Corps of Engineers explained, various types of molluscicides typically have similar modes of action. Molluscicides, sometimes referred to as bait, are touched or ingested by the slug or snail, then the chemicals manipulate the water balance of the animal. By affecting the amount of water in the mollusk’s body, the molluscicides put the slugs or snails on the path to organ failure and inhibit healthy body functions.

There are two forms of chemical molluscicides: oxidizing and non-oxidizing. The non-oxidizing are among the most popular because they’re more cost efficient. Although expensive in small quantities, non-oxidizing molluscicides are more effective in these small doses.

The Army Corps of Engineers outlined some of the most common non-oxidizing molluscicides including:

  • Quanternary and polyquaternary ammonium compounds
  • Aromatic hydrocarbons
  • Endothall as the mono salt
  • Metals like copper sulfate and their salts
  • Niclosamide.

Oxidizing compounds that can be used to combat snail and slug infestations include chlorine, chlorine dioxide, chloramines, ozone, bromine, hydrogen peroxide and potassium permanganate, according to the Army Core Engineers.

One of the most commonly used chemicals in molluscicides is metaldehyde. Used in Antimillace, Ariotox, Deadline, Halizan, Limatox, Namekil and Slug-Tox, this chemical has been popular since the late 1960s for attracting and killing slugs and snails.

Other uses for molluscicides
Aside from slugs and snails in the garden or on a farm, mollusks can also harm commercial and industrial business in bodies of water, Marrone Bio innovations explained. Mollusks can clog pipes, damage equipment and costs businesses significant amounts of money in lost efficiency.

Often people turn to molluscicides to get rid of these pests and keep business profitable. However, there are a variety of environmental factors to consider to avoid wide-spread pollution in the waterway.