Wet weather heralds busy season for slug researcher

Mateusz Perkowski

Capital Press

Published on November 21, 2016 5:36PM

Courtesy of Rory McDonnell
Oregon State University assistant professor Rory McDonnell specializes in slugs. He’s currently helping Oregon farmers find efficient ways to kill the slimy pests.

Courtesy of Rory McDonnell Oregon State University assistant professor Rory McDonnell specializes in slugs. He’s currently helping Oregon farmers find efficient ways to kill the slimy pests.


It’s the rainy season in Oregon, which means there’s plenty of work for Oregon State University’s new slug expert, Rory McDonnell.

With slugs emerging from their underground hibernation, McDonnell has found that Oregon’s reputation as a haven for the slimy pests is well deserved.

“The populations are very large,” he said.

The number and size of slugs is greater in Oregon compared to McDonnell’s previous post as a research specialist at the University of California-Riverside.

“Sometimes, in California, I felt like I was trying to fit a square peg into a round hole,” he said.

McDonnell assumed his new position as an assistant professor at OSU in mid-July, but autumn is when his research began in earnest.

During the dry season, he got his laboratory equipped and met with farmers afflicted by the prodigious mollusks.

The wet weather has now allowed him to study the slug’s life cycle with the aim of developing efficient ways to eliminate the pests.

Slug activity peaks in fall and spring, so McDonnell is out in the field, checking traps to see which species are most problematic in certain locations.

European brown garden snails are the worst offenders in nurseries, while gray field slugs are the primary culprits in field crops, he said.

Indeed, the gray slug is likely the most prominent slug pest worldwide due to its ability to adapt to a variety of environments and food sources, McDonnell said.

“It can be successful under a wide range of conditions,” he said.

In March 2015, OSU organized a “slug summit” in Salem, Ore., where growers complained that damage from slugs has intensified in recent years.

That complaint prompted the university to seek additional funding from Oregon lawmakers to hire a slug researcher. The Legislature provided an addition $14 million to OSU later that year, allowing the university to fill this slug position and several others.

McDonnell is exploring strategies to fight the pests.

For example, farmers could use extracts from food or slug pheromones to attract them to a certain area of a field that’s treated with a hefty dose of molluscicide. This approach may kill the slugs more effectively than spreading a lesser concentration of molluscicide across an entire field.

McDonnell and other researchers have identified slug attractants that work in the laboratory, and they plan to see if the substance also works outdoors.

“What happens in the lab isn’t necessarily what happens in the field,” he said.

Another technique would involve parasitic nematodes that kill slugs, which are used for biocontrol in Europe.

If such nematodes were found in Oregon, researchers would have to prove to the USDA’s Animal and Plant Health Inspection Service that the parasites don’t affect native species.

“We only want to use tools that are safe and specific to the pest species,” McDonnell said.



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