Slugs and snails, destructors of crops and gardens, could be controlled by bread dough

New research from the Oregon State University Extension Service found that slugs and snails are strongly attracted to bread dough. This discovery could lead to better ways of controlling these severe pests in agriculture, nurseries, and home gardens.

Since the beginning of recorded history, slugs have ravaged crops and today are responsible for billions of dollars in damage – including between $60-$100 million to Oregon’s valuable grass seed industry alone, according to Rory Mc Donnell, associate professor and Extension gastropod specialist.

“Damage to grass seed is a major issue,” said Mc Donnell, who collaborated with scientists from other states on a study published in a special issue of Insects that focuses on slugs and snails. “But that’s just one crop. It’s mind-boggling when you think about it. A huge array of crops is affected. They even take out specialty crops like mint. Many times, I’ve seen farmers lose an entire crop.”

Nurseries, farmers, and home gardeners use commercial baits like metaldehyde, iron phosphate, or sodium ferric EDTA to control slugs and snails. These molluscicides are relatively expensive, can be toxic to non-targets, and work with varying degrees of success, Mc Donnell said. Given its simplicity, low cost, and the ready availability of its ingredients, bread dough has the potential for crop protection in the United States and developing countries where pesticide access is limited by cost. A dry formulation would likely have an indefinite shelf life and be easy to ship. It can attract the slugs to a trap, where they will die, or to attract them to molluscicides.

“Bread dough is a nontoxic, generic, and effective tool that could be used in detecting and managing gastropods worldwide,” Mc Donnell said. “It represents a tool to manage pest gastropod infestations, using baited traps or attract-and-kill approaches. It could also be incorporated into existing baits to improve their attractiveness.”

Of the 28 exotic or non-native slug and snail species in Oregon, two are particularly troublesome – European brown garden snails (Cornu aspersum) and gray field slugs (Deroceras reticulatum), which plague nurseries and feed on hundreds of essential crops with a high financial cost. If European brown garden snails are found in shipments of Oregon nursery plants at ports of entry in other states, the items are either shipped back or treated in place, Mc Donnell said. Either way, it’s expensive.

“With worldwide trade and travel, we are getting a homogenization of slugs and snails on planet Earth because of the widespread introduction of species,” Mc Donnell said. “This is not just a modern phenomenon. Slugs and snails have been traveling with humans for thousands of years. But it’s getting more severe because of purposeful introductions, global trade, intensification of agriculture, and development of new crops.”

Mc Donnell and his collaborators haven’t determined yet why bread dough—a simple mixture of flour, water, and yeast—attracts slugs and snails, but they theorize that fermentation draws them. They used a range of foods in addition to bread dough to determine which would be the most attractive bait, including beer, cucumber, lettuce, strawberries, citrus, tomatoes, hostas, and Marmite (a yeast-based food product popular in Great Britain).

“We gave them a choice of food, and they consistently went for the bread dough,” Mc Donnell said. “They like it. They went bonkers for it. Bread dough outperformed everything.”

According to Mc Donnell, over 18,000 snails were trapped in 48 hours in one instance. The research revealed that bread dough can be effective in the field in Oregon for at least eight days.

“It has something we call ‘good field life,’” Mc Donnell said. “That’s important. If it worked for 12 hours, that would be good, but eight days gives a much bigger window for use.”

The project was a collaboration between Mc Donnell and his team; Robin Veasey and Jocelyn Millar, University of California at Riverside; Arnold Hara, University of Hawaii at Hilo; Amy Roda, U.S. Department of Agriculture, Miami; Gary Adams, U.S. Department of Agriculture, Billings, Mont .; and Ian Foley, Montana Department of Agriculture. This work was supported by funding from the U.S. Department of Agriculture under the Plant Protection Act Section 7721.

Author Bio

Kym Pokorny, Communications Specialist for Oregon State University

Public Service Communications Specialist